American Journal of Surgical Pathology

CTNNB1 Mutations and Aberrant β-Catenin Expression in Ovarian Endometrioid Carcinoma

CTNNB1 mutations and aberrant β-catenin expression have adverse prognosis in endometrial endometrioid carcinoma, and recent evidence suggests a prognostic role of β-catenin in ovarian endometrioid carcinoma. Thus, we aimed to determine the prognostic value of the CTNNB1 mutational status, and its correlation with β-catenin expression, in a well-annotated cohort of 51 ovarian endometrioid carcinomas. We performed immunohistochemistry for β-catenin and developed an 11-gene next-generation sequencing panel that included whole exome sequencing of CTNNB1 and TP53. Results were correlated with clinicopathologic variables including disease-free and disease-specific survival. Tumor recurrence was documented in 14 patients (27%), and cancer-related death in 8 patients (16%). CTNNB1 mutations were found in 22 cases (43%), and nuclear β-catenin in 26 cases (51%). CTNNB1 mutation highly correlated with nuclear β-catenin (P<0.05). Mutated CTNNB1 status was statistically associated with better disease-free survival (P=0.04, log-rank test) and approached significance for better disease-specific survival (P=0.07). It also correlated with earlier International Federation of Gynecology and Obstetrics stage (P<0.05). Nuclear β-catenin, TP53 mutations, age, ProMisE group, surface involvement, tumor grade and stage also correlated with disease-free survival. There was no association between membranous β-catenin expression and disease-free or disease-specific survival. CTNNB1 mutations and nuclear β-catenin expression are associated with better progression-free survival in patients with OEC. This relationship may be in part due to a trend of CTNNB1-mutated tumors to present at early stage. β-catenin immunohistochemistry may serve as a prognostic biomarker and a surrogate for CTNN1B mutations in the evaluation of patients with ovarian endometrioid neoplasia, particularly those in reproductive-age or found incidentally without upfront staging surgery.

Endometrial Carcinomas with a “Serous” Component in Young Women Are Enriched for DNA Mismatch Repair Deficiency, Lynch Syndrome, and POLE Exonuclease Domain Mutations

Endometrial carcinoma (EC), as described by Bokhman, has historically been classified as Type I (low-grade, hormone-dependant, young patients, good prognosis) or Type II (high-grade, hormone-independent, older patients, poor prognosis). This classification is no longer pragmatic, however, as EC is a much more heterogeneous disease. Four molecular subtypes of EC were identified by The Cancer Genome Atlas (TCGA), and subsequent studies have demonstrated its utility in predicting prognosis. While endometrial serous carcinoma (ESC), the prototypical Type II EC, largely occurs in older women, younger women with ESC were not accounted for in the Bokhman model and were underrepresented in the TCGA study. We hypothesized that a subset of ESCs in young patients do not represent bona fide serous carcinomas but rather high-grade endometrioid carcinomas mimicking a serous phenotype. We identified ESCs and mixed endometrioid/serous carcinomas in women <60 years (n=37), and analyzed their clinical, morphologic, immunohistochemical, and molecular characteristics. Sixteen percent showed mismatch repair deficiency (MMR-D) and 11% were diagnosed with Lynch syndrome. Additionally, 16% of cases tested harbored a hotspot POLE exonuclease domain mutation (POLE-EDM). Morphologically, 47% of tumors showed confirmatory endometrioid features, including atypical hyperplasia, a low-grade endometrioid carcinoma component, or squamous differentiation. Clinically, the overall survival in patients with MMR-D and POLE-EDM was significantly better than that of patients without these features (P=0.0329). In conclusion, ESCs in young patients comprise a heterogeneous group of tumors, demonstrating diverse clinical, immunohistochemical, morphologic, and molecular features which have implications for prognosis and adjuvant therapy.

SOX2 Is the Most Sensitive Biomarker in Testicular and Gynecologic Embryonic-type Neuroectodermal Tumors (ENT) Based on a Comprehensive Evaluation of Biomarker Expression

Embryonic-type neuroectodermal tumor (ENT; previously referred to as primitive neuroectodermal tumor, PNET) of the testis and gynecologic tract share morphologic features with small round blue cell tumors, including Ewing sarcoma (ES), yet are biologically, therapeutically, and prognostically distinct. The diagnosis of ENT can be challenging, and it is unclear if there are reliable biomarkers that can be used to confirm this diagnosis. This study characterized 50 ENTs arising from the testis (n=38) and gynecologic tract (n=12; 7 ovary/5 uterus) with 27 biomarkers (AE1/AE3, ATRX, CD99, chromogranin-A, Cyclin D1, Fli-1, GFAP, GLUT-1, IDH1/2, INSM1, MTAP, NANOG, Nestin, neurofilament, NKX2.2, NSE, OCT3/4, OLIG2, p16, PAX6, PHOX2B, S100, SALL4, SOX2, SOX10, SOX17, synaptophysin). Expression was evaluated for extent (0, negative; 1, ≤10% positive; 2, 11% to 50% positive; 3, >50% positive) and intensity (1, weak; 2, moderate; 3, strong) of staining to obtain a combined score (CS) of 0-9; a CS ≥4 was considered “significant staining.” SOX2 was the most sensitive biomarker for ENT, as 85% of the tumors demonstrated CS=9. GLUT-1, Fli-1, SALL4, and Cyclin D1 also showed CS ≥4 in more than half of the ENTs; however, only a minority demonstrated CS=9. All other biomarkers showed CS ≥4 in fewer than half of the ENTs, including synaptophysin (38%), GFAP (15%), S100 (15%), and chromogranin-A (14%). NKX2.2, CD99, and SOX17 showed CS ≥4 in 7%, 0%, and 3% of tumors, respectively. Overall, we found that in the appropriate clinicopathologic context, utilizing a panel of SOX2, OCT3/4 (to exclude embryonal carcinoma), AE1/AE3, NKX2.2, CD99, and SOX17 could be helpful in the diagnosis of ENT; many other traditional diagnostic biomarkers show limited utility.

Low-Grade Endometrial Stromal Sarcoma

Low-grade endometrial stromal sarcomas (LG-ESS) are the second most common malignant uterine mesenchymal tumors, but in contrast to the more common leiomyosarcomas, they are often characterized by a prolonged and relatively indolent course. However, a subset of patients experience significant morbidity or die of disease, and it is difficult to predict which tumors will behave aggressively, with most published studies limited in either the number of tumors or the depth of pathologic parameters evaluated. Thus, we studied the clinicopathologic features of LG-ESS in 102 patients ranging from 21 to 74 (median: 47) years. All were treated with hysterectomy and staged according to both the FIGO 2018 system (stage IA=22, IB=36, I-not otherwise specified=5, II=16, III=13, IV=10) and the FIGO 1988 system (stage I=62, II=1, III=17, IV=22). Tumors measured 1.2-49 (median: 7) cm. Microscopically, 69 involved the endometrium while 33 were centered in the myometrium. Thirteen showed only minimal infiltration of the myometrium while the rest displayed the typical extensive myometrial permeation. The cervical stroma was involved in 18, the uterine serosa in 27, and the parametrium in 22. Conventional morphology resembling proliferative endometrial stroma was seen in 95, fibroblastic appearance in 35, smooth muscle differentiation in 23, sex cord-like differentiation in 21, stromal hyalinization in 21, and myxoid stroma in 9. Less common features included glandular differentiation resembling adenomyosis (n=5), pseudopapillary pattern (n=1), deciduoid appearance (n=2), adipocytic differentiation (n=2), multinucleated cells (n=2), and rhabdomyoblastic differentiation (n=1). Mitoses ranged from <1 to 20 per 10 high-power fields (median=3). Lymphovascular invasion and infarct-type necrosis were present in 64 and 23, respectively. Follow-up was available in all patients ranging from 16 to 358 (median: 79) months. Forty-six received adjuvant treatment as hormonal therapy (n=34), radiation (n=4), radiation and hormonal therapy (n=4), chemotherapy (n=3), or chemotherapy and radiation (n=1). Three patients had persistent unresected tumor following surgery, and an additional 34 had recurrences at intervals of 3 to 272 (median: 79) months, including 2 tumors with minimal infiltration. At last follow-up, 75 patients were alive with no evidence of disease, 14 were alive with disease, and 9 died of disease at intervals of 16 to 167 (median=70) months. Four died of unrelated causes without recurrence. Five-year recurrence-free survival (RFS) and disease-specific survival (DSS) were 80% and 94%, while 10-year RFS and DSS were 51% and 87%, respectively. On statistical analysis, cervical stromal involvement (P=0.018) and myxoid stroma (P<0.001) were associated with shorter recurrence-free survival. Tumors lacking a conventional component had worse disease-specific survival (P=0.048). All other clinical and morphologic features, including stage, were not significantly associated with outcome. On multivariate analysis, only cervical stromal involvement remained an independent predictor of recurrence-free survival (P=0.047; HR: 16.939) and no factors were independently predictive of disease-specific survival. Our findings highlight the difficulty in predicting outcomes in these tumors, likely due to slow progression and frequent treatment responses even in the recurrent setting. We confirm the potential for recurrence even in tumors initially showing minimal infiltration. Cervical stromal involvement and lack of conventional morphology are potential novel risk factors that should be further evaluated in subsequent studies.

The Evolving Spectrum of Endometrial Glandular Proliferations With Corded and Hyalinized Features

We present the clinicopathologic and immunohistochemical features of 14 endometrial glandular proliferations with conspicuous corded and hyalinized (CH) features comprised entirely or predominantly of endometrial hyperplasia. Endometrial glandular lesions ranged in severity from endometrial hyperplasia with and without cytologic atypia (5/14 [36%]) to hyperplasia with architectural complexity bordering on well-differentiated endometrioid adenocarcinoma (3/14 [21%]) to frank corded and hyalinized endometrial carcinoma (“CHEC”) (6/14 [43%]). In addition to sex cord–like growth and hyalinized stroma, other common histologic features included prominent spindle cells (11/14 [79%]), keratinizing and/or morular squamous differentiation (10/14 [71%]), and osseous metaplasia (6/14 [43%]). Immunohistochemical characterization revealed aberrant nuclear beta-catenin in all cases (14/14 [100%]); additionally, all cases demonstrated positive estrogen receptors, intact PTEN, PMS2 and MSH6, and wild-type p53 expression. Patients ranged in age from 24 to 58 (mean 38) years. Of 5 patients with hyperplasia with CH features, 2 experienced complete resolution after progestin therapy and none progressed to adenocarcinoma (mean follow-up 15.6 mo, range 2 to 64). By contrast, of 2 patients with hyperplasia bordering on CHEC and with available follow-up, both subsequently developed adenocarcinoma, suggesting that even focal increased architectural complexity may predict an elevated risk of malignancy. We conclude that CH morphology is not limited to endometrioid carcinoma and may occur across a spectrum of neoplastic proliferations, including those without sufficient architectural complexity or cytologic atypia to warrant classification as adenocarcinoma. We propose the term “corded and hyalinized endometrial hyperplasia” to describe this precursor lesion and report favorable outcomes with conservative treatment.

Endometrial Stromal Sarcomas With BCOR Internal Tandem Duplication and Variant BCOR/BCORL1 Rearrangements Resemble High-grade Endometrial Stromal Sarcomas With Recurrent CDK4 Pathway Alterations and MDM2 Amplifications

The distinction between low-grade and high-grade endometrial stromal sarcomas (LGESS, HGESS) is increasingly defined by genetics. Recently, variant genomic alterations involving BCOR or BCORL1 have been reported in endometrial stromal sarcoma (ESS), although it remains unclear whether these justify a diagnosis of LGESS or HGESS. In this study, we describe clinicopathologic and molecular features of ESS with such alterations to help clarify their classification in the spectrum of ESS. We collected a cohort of 13 ESS harboring variant alteration involving BCOR (6 with internal tandem duplication, 1 with EP300::BCOR fusion, 1 with BCOR::LPP fusion) and BCORL1 (4 with JAZF1::BCORL1 fusion, 1 with EPC1::BCORL1 fusion). The median patient age at primary diagnosis was 51 years (range: 18 to 70 y). Median tumor size at primary diagnosis was 9.3 cm (range: 4.5 to 21 cm), and extrauterine disease spread (stage IIIB-C) was present in 27%. The tumors were composed of round to spindled cells with cellularity and cytologic atypia ranging from mild to marked and a median mitotic count of 18/10 HPFs (range: 2 to 85/10 HPFs). At least focally myopermeative growth was noted in 8/8 assessable cases. Of 12 patients with follow-up data (median: 25 mo), 4 patients died of disease and 3 were alive with recurrent disease. Unsupervised hierarchical clustering of DNA methylation data together with a large cohort of uterine mesenchymal tumors that included YWHAE::NUTM2 and ZC3H7B::BCOR HGESS and molecularly confirmed LGESS revealed a common methylation signature for all ESS with variant BCOR and BCORL1 alterations and HGESS with YWHAE::NUTM2 and ZC3H7B::BCOR gene fusion. Copy number analysis revealed amplifications of CDK4 and MDM2, as well as homozygous deletions of CDKN2A/B and NF1 in a subset of tumors. Our results indicate that ESS with BCOR internal tandem duplication and variant BCOR and BCORL1 rearrangements clinically and molecularly resemble conventional HGESS.

SALL4 as a Useful Marker for the Distinction of Various Gestational Trophoblastic Disease Subtypes

The distinction between choriocarcinoma and residual trophoblastic cell proliferation from a complete hydatidiform mole/invasive mole (CHM/IM) without villi is challenging on curettage materials. We investigated whether SALL4 immunostaining could help differentiate various gestational trophoblastic diseases. Placental site nodules (PSN; n=10), atypical PSN (APSN; n=8), placental site trophoblastic tumors (PSTT; n=9), epithelioid trophoblastic tumors (ETT; n=5), gestational choriocarcinomas (n=31), partial hydatidiform moles (PHM; n=13), CHM/IM (n=47), and nonmolar products of conception (POC) (n=26) were included. SALL4 immunostaining was quantified (0 [1% to 10%], [11% to 100%]) and characterized (scattered single-cell or clustered nuclear positivity) in 2 locations: cytotrophoblast/intermediate trophoblast and villous stromal fibroblasts. A diffuse (11% to 100%) and clustered pattern of SALL4 immunostaining in cytotrophoblast/intermediate trophoblast was statistically associated with choriocarcinomas (74.2%, 23/31) as compared with PSN (0/10; P<0.0001), APSN (0/8; P=0.0002), PSTT (0/9; P<0.0001), ETT (0/5; P=0.0034), PHM (0/13; P<0.0001), CHM/IM (0/47; P<0.0001), and nonmolar POC (0/26; P<0.0001). Most nonchoriocarcinoma samples showed no SALL4 expression; when present, it was of low level (1% to 10%) and with a scattered single-cell staining in 3/9 PSTT (33%), 1/13 PHM (7.7%), 19/47 CHM/IM (40%), and 1/26 nonmolar POC (1.7%). These results were confirmed using a validation cohort. In addition, 66% (31/47) of CHM/IM villous stromal fibroblasts showed SALL4 expression (11% to 100%) (all before 14 gestational weeks), whereas this level of expression was never observed in PHM (0/13), nor in nonmolar POC (0/26; P<0.0001). Finally, a clustered and >10% SALL4 immunostaining in cytotrophoblast/intermediate trophoblast favors choriocarcinoma diagnosis. SALL4 expression in >10% villous stromal fibroblasts before 14 gestational weeks favors CHM/IM rather than PHM and nonmolar POC.

Secondary Involvement of the Uterine Cervix by Nongynecologic Neoplasms

Secondary involvement of the uterine cervix by nongynecologic neoplasms is rare accounting for <2% of metastases to the gynecologic tract. This study aimed to analyze the clinicopathologic features of cervical involvement by nongynecologic malignancies. A total of 47 cases were identified including 39 (83%) carcinomas, 6 lymphomas (12.8%), and 2 (4.2%) cutaneous malignant melanomas. The most common primary site of origin among carcinomas was the gastrointestinal tract (27, 69.2%), followed by breast and urothelium (5 each, 12.8%), gallbladder, and lung (1 each, 2.6%). The gynecologic tract was involved at the presentation in 16 patients (34%), including 5 (10.6%) with the cervix being the first site, 7 (14.9%) with synchronous involvement of the cervix and other gynecologic sites, and 4 (8.5%) with the involvement of other gynecologic sites before the cervical presentation. Patients with lymphoma were younger compared with those with carcinoma (43.7 vs. >50.5) (P=0.01). Mean time to identification of cervical metastases was <1 year for gallbladder carcinoma, melanomas, and gastrointestinal signet ring cell carcinomas (P=0.03). Features that varied with different types of metastatic tumor included lymphovascular space invasion, depth of stromal invasion, growth pattern (glands lacking architectural complexity, cribriforming, solid), presence of goblet cells, and signet ring cells, degree of cytologic atypia, and overall findings mimicking a benign/noninvasive process (P≤0.027). Six tumors (12.8%) were initially misdiagnosed as cervical primary. Metastatic nongynecologic tumors can mimic primary in situ or invasive neoplasms in both ectocervix and endocervix. In patients with a known prior malignancy, the clinical history with ancillary studies and a high level of suspicion are crucial to ensure accurate diagnosis.

BRG1, INI1, and ARID1B Deficiency in Endometrial Carcinoma

Switch/sucrose nonfermenting complex subunits, such as BRG1, INI1, and ARID1B, are inactivated in a subset of endometrial undifferentiated carcinoma and dedifferentiated carcinoma (DC). Limited information is currently available on their prevalence in other subtypes or the nosological status of endometrial carcinoma with their deficiencies. This study immunohistochemically examined the expression status of BRG1, INI1, and ARID1B using 570 archived cases of endometrial carcinoma and carcinosarcoma resected at a single institution. We identified 1 BRG1-deficient undifferentiated carcinoma, 8 BRG1/INI1/ARID1B–deficient DC, and 3 BRG1-deficient clear-cell carcinomas. None of the cases of endometrioid and serous carcinomas or carcinosarcoma showed deficiencies of these subunits. We then compared 8 BRG1/INI1/ARID1B–deficient DC with 6 BRG1/INI1/ARID1B–intact DC and 28 carcinosarcomas, the latter of which was often confused with DC. Histologically, BRG1/INI1/ARID1B–intact and BRG1/INI1/ARID1B–deficient DC shared a monotonous solid appearance with rhabdoid and epithelioid cells and a myxoid stroma; however, abrupt keratinization and cell spindling was absent in BRG1/INI1/ARID1B–deficient tumors. The median overall survival of patients with BRG1/INI1/ARID1B–deficient DC was 3.8 months, which was worse than those with BRG1/INI1/ARID1B–intact DC (P=0.008) and with carcinosarcoma (P=0.004). BRG1/INI1/ARID1B–deficient DC may be a separate entity with an aggressive behavior to be distinguished from BRG1/INI1/ARID1B–intact DC and carcinosarcoma. Regarding clear-cell carcinoma (n=12), BRG1 deficiency appeared to be mutually exclusive with abnormal ARID1A, BRM, and p53 expression. Further studies are needed to clarify whether BRG1 deficiency plays a role in the pathogenesis of clear-cell carcinoma.

DNA Mismatch Repair–deficient Endometrial Carcinosarcomas Portend Distinct Clinical, Morphologic, and Molecular Features Compared With Traditional Carcinosarcomas

Uterine carcinosarcomas (UCSs) are aggressive neoplasms composed of high-grade malignant epithelial and mesenchymal elements with most (∼90%) showingTP53abnormalities. A subset, however, shows mismatch repair deficiency (MMR-D). We sought to describe their clinical, morphologic, and molecular features. Clinicopathologic data of MMR-D UCSs were recorded including age, stage, follow-up, mismatch repair and p53 immunohistochemistry (IHC),MLH1promoter methylation status, and germline alterations,TP53mutation status, microsatellite instability and mutational burden by massively parallel sequencing. Seventeen (6.2%) MMR-D were identified among 276 UCSs. Of MMR-D UCSs, the median age was 60 years. mismatch repair IHC loss is as follows: MLH1/PMS2 65%, MSH2/MSH6 18%, MSH6 12%, and PMS2 6%.MLH1promoter methylation and Lynch syndrome was identified in 47% and 12% of cases, respectively. Cases with p53 IHC showed the following patterns: wild-type 70%, aberrant 20%, and equivocal 10%. Of cases with sequencing, 88% were hypermutated and microsatellite instability high. High-grade endometrioid, undifferentiated, and clear cell carcinoma was present in 53%, 41%, and 6% of cases, respectively and 47% also showed a low-grade endometrioid component. Most patients presented at an early stage (67%) and upon follow-up, 18% died of disease, 65% showed no evidence of disease, while 18% are alive with disease. Patients with MMR-D UCS are younger than the reported median age (70 y) for traditional UCS and most do not show p53 abnormalities. Low-grade endometrioid and undifferentiated carcinoma were seen in approximately half of all cases. Although UCSs have a high tendency for early extrauterine spread, most patients in our cohort presented at an early stage and at follow-up were no evidence of disease. MMR-D UCSs display distinct clinical, morphologic, and molecular features compared with traditional UCSs.

Uterine Tumor Resembling Ovarian Sex Cord Stromal Tumor (UTROSCT)

ESR1 and GREB1 fusions have recently been described in uterine tumor resembling ovarian sex cord tumor (UTROSCT). Thus far, recurrences have been documented in a subset of those harboring GREB1 fusions, but not in those with ESR1 rearrangements. Here we describe the clinicopathologic features of 3 recurrent UTROSCTs with striking rhabdoid morphology (an unusual feature of these tumors overall) and ESR1-NCOA2 fusions. The patients were 32, 37, and 54 years at initial diagnosis and first recurrence occurred at 7, 9, and 32 years. The primary tumors (available in two cases) were centered in the myometrium and showed infiltrative borders. They predominantly grew in sheets and cords, but also had a pseudopapillary appearance. Cells were uniformly epithelioid with eccentric nuclei, prominent nucleoli, abundant eosinophilic globular/glassy (rhabdoid) cytoplasm, and infrequent mitoses (≤4/10 high-power fields [HPFs]). Recurrences were morphologically identical to the primary tumors, but demonstrated brisk mitotic activity (≥16/10 HPFs). The third tumor (with only recurrences available) had multiple patterns, including diffuse, corded, trabecular, and a focal retiform growth. Rhabdoid cells were conspicuous, but only comprised ~50% of the tumor, and mitoses numbered up to 2/10 HPFs. All tumors were strongly and diffusely positive for WT1, CAM5.2, ER, and PR, but negative for inhibin. Diffuse calretinin and desmin expression, as well as focal melan-A positivity, was noted in one tumor, but was negative in the others. In all 3 tumors, INI-1 and BRG-1 were retained, and ESR1-NCOA2 fusions were detected by targeted RNA sequencing. This study is the first to highlight an association between UTROSCTs with extensive rhabdoid differentiation, ESR1-NCOA2 fusions, and aggressive behavior. UTROSCTs are considered neoplasms of uncertain malignant potential, but have a benign course in most cases. Thus, it is important to be aware of these specific features and recommend long-term follow-up due to their propensity for late recurrences.

Molecular Profiles of Mixed Endometrial Carcinoma

Mixed endometrial carcinomas are defined as a combination of 2 or more distinct histologic subtypes, one of which must be a type II tumor comprising at least 5% of the tumor volume. The oncogenesis of these tumors remains unclear, particularly in light of the increasingly appreciated morphologic overlap among subtypes, as well as evolving molecular data. We evaluated 8 cases of mixed endometrial carcinoma, including 4 endometrioid (EC)/serous (SC), 1 SC/clear cell (CC), and 3 EC/CC cases, to study the underlying molecular features and oncogenic mechanisms at play. Each component was analyzed by a targeted next-generation sequencing assay. All tumors shared mutations in both components. In 6 cases, one component showed additional mutations. Two EC/SC cases showed shared mutations and mutations unique to each component. When present, unique mutations were typically seen in the SC component, including variants in POLE and TP53, as well as potentially targetable genes DDR2, MAP2K1, and CCNE1. In EC/SC tumors, ERBB2 abnormalities were seen in 2 cases. EC/CC cases showed FGFR2 activating mutations in the EC component only. No fusion drivers were identified. Our data suggest that the majority of these tumors begin as a single clone and diverge along 2 pathways: (1) tumor progression, with one component showing additional mutations, and (2) tumor divergence, in which tumor components have both shared mutations and mutations unique to each component. In addition, the findings suggest a component of morphologic mimicry in these tumors. Our findings are clinically relevant since targetable mutations may be present in only one component of mixed tumors.

PD-L1 Expression and CD8+ Tumor-infiltrating Lymphocytes in Different Types of Tubo-ovarian Carcinoma and Their Prognostic Value in High-grade Serous Carcinoma

The prevalence and significance of programmed death-1 ligand (PD-L1) expression in different types of tubo-ovarian carcinoma have not been well defined. We evaluated PD-L1 expression and CD8+ tumor-infiltrating lymphocyte (TIL) density in whole tissue sections of 189 cases of tubo-ovarian carcinoma, including high-grade serous carcinoma (HGSC, n=100), clear cell carcinoma (CCC, n=24), endometrioid carcinoma (EmC, n=40), and mucinous carcinomas (MC, n=25). Using the tumor proportion score (TPS) with a 1% cutoff, PD-L1 expression was present in 21% of HGSC, 16.7% of CCC, 2.5% of EmC, and 4% of MC. Using the combined positive score (CPS) with a cutoff of 1, PD-L1 expression was present in 48% of HGSC, 25% of CCC, 20% of EmC, and 24% of MC. HGSC demonstrated significantly higher CD8+ TIL density than CCC (P=0.013238), EmC (P=0.01341), or MC (P=0.004556). In HGSC, CD8+ TIL density was directly correlated with PD-L1 positivity using either TPS (P=0.0008) or CPS (P=0.00011). Survival analysis of patients with high stage (stage III to IV) HGSC revealed PD-L1 positivity by TPS to be associated with improved progression-free survival (adjusted hazard ratio: 0.4912 vs. 2.036, P=0.0378). Although not statistically significant, a similar trend was observed in overall survival (adjusted hazard ratio: 0.3387 vs. 2.953, P=0.0548). In contrast, with CPS, no significant difference was identified between PD-L1-positive and negative groups in either progression-free survival (P=0.5086) or overall survival (P=0.7823). Neoadjuvant chemotherapy was associated with higher PD-L1 expression by TPS (P=0.00407) but not CPS. No significant difference in PD-L1 expression was detected in tumors from patients with germline BRCA1/2 mutations compared with germline mutation-negative tumors by either TPS or CPS. In conclusion, the prevalence of PD-L1 expression is variable in different types of tubo-ovarian carcinoma and is highest in HGSC. In high-stage HGSC, PD-L1 positivity in tumor cells is associated with an increased immune response and improved survival.

Molecular Heterogeneity of Endometrioid Ovarian Carcinoma

Endometrioid ovarian carcinoma (EOC) has clinical and biological differences compared with other histologic types of ovarian carcinomas, but it shares morphologic and molecular features with endometrioid endometrial carcinoma. To analyze the molecular heterogeneity of EOC according to the new molecular classification of endometrial cancer and to evaluate the prognostic significance of this molecular classification, we have analyzed 166 early-stage EOC by immunohistochemistry for mismatch repair proteins and p53 expression, and by Sanger sequencing for the exonuclease domain of polymerase epsilon (POLE EDM). In addition, we have carried out next-generation sequencing analysis of tumors with POLE EDM mutations to confirm the ultramutated profile. Eight tumors carried POLE EDM mutations and were classified as ultramutated (5%), 29 showed mismatch repair deficiency and were classified as hypermutated (18%), 16 tumors had a mutated pattern of p53 expression and were classified as p53 abnormal (11%), and 114 tumors did not have any of the previous alterations and were classified as no specific type (66%). Five tumors showed >1 classification criteria. The frequencies of ultramutated and hypermutated tumors were lower in EOC compared with the frequency reported in endometrial cancer. Subrogate molecular groups differed in both morphologic features (histologic grade, squamous and morular metaplasia, and necrosis) and immunohistochemical expression of several biomarkers (ARID1A, nuclear β-catenin, estrogen receptors, Napsin A, and HINF1B). In addition, the number of CD8+ tumor-infiltrating lymphocytes was higher in ultramutated and hypermutated tumors. The most commonly mutated genes in the ultramutated group were ARID1A (100%), PIK3R1, PTEN, BCOR, and TP53 (67% each), whereas no mutations were detected in KRAS. Although the prognosis did not differ among subgroups in the multivariate analysis, a trend toward a better prognosis in POLE-mutated and a worse prognosis in p53 abnormal tumors was observed. In addition, this classification could have important therapeutic implications for the use of immunotherapy in tumors classified as ultramutated and hypermutated.

Endometrial Gastric-type Carcinoma

BCOR Expression in Mullerian Adenosarcoma

Adenosarcoma can mimic high-grade endometrial stromal sarcoma with ZC3H7B-BCOR fusion that may show entrapped glands and often exhibits diffuse BCOR expression. We encountered diffuse BCOR expression in rare adenosarcomas and sought to define its frequency among a larger cohort of these tumors. BCOR immunohistochemistry was performed on archival formalin-fixed paraffin-embedded tumor tissue in 13 of 14 adenosarcomas with and without stromal overgrowth arising in the uterus or ovary. The staining intensity and percentage of positive tumor nuclei in the mesenchymal component were evaluated. Eleven cases with sufficient tumoral tissue were subjected to fluorescence in situ hybridization for the detection of BCOR, BCORL1, NUTM1, ZC3H7B, and JAZF1 rearrangement. Three cases were subjected to targeted RNA sequencing. BCOR was expressed in 9 of 13 (70%) tumors, including 6 with and 3 without stromal overgrowth. Moderate to strong staining in >70% of cells was seen throughout in 1 low-grade and 6 high-grade tumors, 5 of which had stromal overgrowth. No staining was seen in 3 low-grade and 1 high-grade tumors with stromal overgrowth. One tumor demonstrating extensive sex cord-like differentiation and diffuse BCOR expression harbored JAZF1 and BCORL1 rearrangements. No BCOR or BCORL1 rearrangement was identified in the remaining tumors. BCOR expression is seen in most adenosarcomas with and without stromal overgrowth. BCORL1 rearrangement is seen in rare tumors with diffuse BCOR expression. Assessment of BCOR or BCORL1 rearrangement status is required in adenosarcomas demonstrating BCOR expression.

Mesonephric-like Carcinoma of the Endometrium

Endometrial mesonephric-like carcinomas (MLCa) are uncommon with <50 reported cases thus far. Previous studies have characterized the histologic, immunohistochemical, and molecular features of MLCa; however, there is limited information with respect to outcome. This single-institution study of 23 uterine MLCas characterizes the behavior of such a neoplasm. Uterine MLCas (2004-present) had review of histologic features, immunohistochemical results, molecular profile, and clinical information (stage, treatment, follow-up). The behavior of MLCa was compared with low-grade endometrioid carcinomas (ECas) and uterine serous carcinomas (USCs) treated at our institution from 2004 to present. All MLCas had a mixture of previously described architectural and cytologic features most notably ductal and/or tubular architecture (21/23), nuclei resembling those of papillary thyroid carcinoma (18/23), and at least focal intraluminal eosinophilic secretions (20/23). Immunoperoxidase studies facilitated diagnosis in 22 cases: CD10, 10/10; calretinin, 5/15; estrogen receptor (≥10% nuclei), 6/21; progesterone receptor, 1/15; GATA-3, 15/16; TTF-1, 11/16. Fourteen of 17 tested cases had a KRAS mutation (7 as the only alteration; 7 with additional mutations including PIK [n=5]; PTEN [n=2], CTNNB1 [n=1]).One case had mutations in PTEN, PIK, and CTNNB1 without KRAS; 2 cases had no detectable somatic mutation. Overall, 48% of patients presented with International Federation of Gynecology and Obstetrics (FIGO) stage 3 or 4 disease with the following uterine risk factors: >50% myometrial invasion, 20/23; lymphovascular space invasion, 16/23; cervical stromal invasion, 7/23. Twenty patients had adjuvant therapy (7 radiation only; 13 chemotherapy±radiation), whereas 3 patients had either unknown or declined therapy. Follow-up was known for 21 patients: 17 patients had recurrences or never achieved remission with the lung being the most common recurrence site (n=9); 7 patients died of disease. The median progression-free survival was 18.2 months for MLCa compared with 183 months for ECa and 67.1 months for USC. The median overall survival for MLCa was 70.6 months compared with 139.1 months for USC (median survival for ECa not reached). Uterine MLCa is uncommon with most tumors recognized by architectural heterogeneity, vesicular, overlapping nuclei with grooves, and eosinophilic luminal secretions. The typical immunoprofile includes low to absent expression of hormone receptors but at least focal expression of GATA-3 and/or TTF-1. Most tested cases had a KRAS mutation although genetic mutations typically associated with ECa are not uncommon. Compared with more commonly encountered types of ECa, MLCa is more aggressive with a tendency towards earlier and distant recurrence.

PD-L1 Expression in Endometrial Carcinoma Cells and Intratumoral Immune Cells

Programmed death-ligand 1 (PD-L1) is a biomarker that may predict the response to anti-programmed death 1/PD-L1 immunotherapy. We evaluated the expression of PD-L1 in carcinoma cells (Ca) and immune cells (ICs) across histopathologic and The Cancer Genome Atlas (TCGA) molecular subgroups of endometrial carcinoma (EC). Our study included 842 patients with EC. Direct sequencing of polymerase epsilon (POLE) exonuclease domain hot spots and conventional immunohistochemistry (MLH1, PMS2, MSH2, MSH6, p53) were conducted to identify TCGA classification–based molecular subgroups of EC: POLE-mutated, mismatch repair deficient, no specific molecular profile, and p53 aberrant. Multiplex immunohistochemistry was performed to evaluate PD-L1 expression in Ca and tumor-infiltrating ICs. PD-L1 expression in Ca and in ICs was detected in 8.6% and 27.7% of the cases, respectively. A combined positive score (CPS) was ≥1% in 19.4% of the samples. PD-L1 positivity in Ca and ICs, and CPS correlated with tumor T-cell density (P<0.001). POLE-mutated and mismatch repair-deficient tumors were more likely to present PD-L1-expressing ICs, CPS positivity, and abundant tumor-infiltrating lymphocytes compared with other TCGA subgroups (P<0.001). No differences existed in Ca-PD-L1 expression (P=0.366). Within various histotypes, non-endometrioid carcinomas displayed the highest Ca-PD-L1, ICs, and CPS (P<0.03). Advanced cancers showed more frequent Ca-PD-L1 positivity (P=0.016), and CPS (P=0.029) and IC≥1% (P=0.037) positivity compared with early disease. In conclusion, PD-L1 expression profiles differ between molecular subclasses, histologic subtypes, and disease stage of EC. Prospective studies are needed to explore the predictive value of various PD-L1 scoring systems within the subgroups of EC. CPS presents methodological advantages over cell type–specific scoring systems.

SMARCA4-deficient Uterine Sarcoma and Undifferentiated Endometrial Carcinoma Are Distinct Clinicopathologic Entities

Undifferentiated and dedifferentiated endometrial carcinomas (UDEC) are aggressive uterine tumors which may show loss of expression of SMARCA4 (BRG1) or SMARCB1 (INI-1). The recently described SMARCA4-deficient undifferentiated uterine sarcoma (SDUS) has a morphology which overlaps with UDEC. In this study, we compared clinical, morphologic, immunohistochemical, and molecular characteristics to identify features which differentiate SDUS from UDEC. Cases of SDUS (n=12) were compared with cases of UDEC (n=84, 55 of which were previously published). Immunohistochemistry was performed for p53, mismatch repair proteins, claudin-4, SMARCA4, and SMARCB1. Targeted molecular profiling was performed on 15 cases. Patients with SDUS were significantly younger than those with UDEC (mean 35.8 vs. 61.2 y, P=0.0001). UDEC and SDUS showed morphologic overlap; however, phyllodiform architecture favored a diagnosis of SDUS (36% vs. 0%, P=0.005), while prominent nuclear pleomorphism was only seen in some cases of UDEC (0% vs. 24%, P=0.15). Compared with SDUS, UDEC more frequently showed TP53 mutations (0% vs. 34%, P=0.03), microsatellite instability (0% vs. 44%, P=0.006), and intact SMARCA4 and SMARCB1 (0% vs. 80%); a panel combining these immunohistochemical markers had a sensitivity of 100% and specificity of 92% in distinguishing SDUS and UDEC. Cases of UDEC had mutations in genes associated with endometrial adenocarcinomas (eg, TP53, PTEN, PIK3CA) and occasionally SMARCA4, while SDUS was characterized solely by inactivating mutations in SMARCA4. Disease-specific survival was shorter in SDUS than UDEC (median survival 9 and 36 mo, P=0.01). In conclusion, SDUS occurs in younger patients than UDEC, has a worse prognosis, and in most cases has a distinct molecular and immunohistochemical profile.

Endometrial Gastric (Gastrointestinal)-type Mucinous Lesions

With the recent elucidation of gastric-type lesions in the female genital tract (especially in the cervix), occasional cases of endometrial adenocarcinoma displaying gastric (gastrointestinal) differentiation have been reported, but they are currently not recognized as a distinct pathologic entity. We report 9 cases of endometrial mucinous lesions which exhibit gastric (gastrointestinal)-type features by morphology and immunohistochemistry, including 4 adenocarcinomas and 5 benign mucinous lesions, in patients aged 32 to 85. The adenocarcinomas showed gastric-type morphology in all 4 cases and goblet cells in 1, with a component of benign gastric-type mucinous glands in 1 case. Immunohistochemically, the adenocarcinomas were positive for CK7 (4/4), CEA (4/4), MUC6 (3/3), PAX8 (3/4), CK20 (2/4), CDX2 (2/4), and estrogen receptor (1/4). They were negative for Napsin A (0/3), with mutation-type p53 staining in 2/4 cases, block-type p16 positivity in 1/4, and scattered chromogranin-positive cells in 1/2. Targeted next-generation sequencing revealed nonsense mutation in RB1 gene for the case with block-positive p16. Follow-up was available in all adenocarcinoma cases and indicated aggressive behavior; 2 patients were dead of disease at follow-up of 7 months to 3 years, 1 was alive with progression at 9 months, and 1 was alive without disease at 7 months. The benign mucinous lesions (including the benign component in 1 adenocarcinoma) exhibited gastric-type morphologic features in 5/6 cases, goblet cells in 5/6, and Paneth-like neuroendocrine cells in 1/6. These benign mucinous lesions were associated with an endometrial polyp in 5/6 cases. Cytologic atypia was present in 2/6 cases and a lobular architecture resembling cervical lobular endocervical glandular hyperplasia in 4/6. Immunohistochemically, the benign mucinous lesions were positive for CK7 (5/5), CDX2 (5/6), estrogen receptor (4/5), MUC6 (4/5), CK20 (3/5), PAX8 (3/5), and CEA (2/4), with scattered chromogranin-positive cells in 4/4 cases; in all cases tested Napsin A was negative, p53 was wild-type and p16 was negative. We propose the term “endometrial gastric (gastrointestinal)-type adenocarcinoma” for this distinctive group of rare aggressive endometrial carcinomas. We believe that benign or atypical gastric (gastrointestinal)-type mucinous lesions are putative precursors for these adenocarcinomas, comparable to recognized premalignant gastric-type lesions in the cervix and the vagina. Future recognition and reporting of these gastric-type endometrial mucinous lesions will help delineate their pathogenesis and clinical significance.

A 3-Tier Chemotherapy Response Score for Ovarian/Fallopian Tube/Peritoneal High-grade Serous Carcinoma

The chemotherapy response score (CRS) is used to score histopathologic response to neoadjuvant chemotherapy (NACT) of patients with extrauterine high-grade serous carcinoma. This study was undertaken to determine if the CRS in the omentum, adnexa or when combined correlates with (1) progression-free survival (PFS) or overall survival (OS), (2) laparoscopic score of abdominal disease, (3) Cancer antigen 125 levels, (4) BRCA status, and (5) platinum-resistant disease. A total of 158 cases were retrospectively collected that received NACT between April 2013 and February 2018 at a single institution. The 3-tier Böhm CRS system was applied to the omentum and adnexa. Survival outcomes between scored subgroups were analyzed using Cox proportional hazards regression. Spearman rank correlation analyses were used to assess CRS and clinical data. A total of 119 cases were treated only with carboplatin/paclitaxel. Omental CRS was: 1 (23 cases, 19.3%), 2 (65 cases, 54.6%), and 3 (31 cases, 26.1%), whereas adnexal CRS was: 1 (50 cases, 42%), 2 (48 cases, 40.3%) and 3 (21 cases, 17.6%). The omental CRS was significantly associated with PFS as a 2-tier score (hazard ratio [HR]=0.612, 95% confidence interval [CI]: 0.378-0.989, P=0.045) but not associated with the PFS using the 3-tier score or with OS using either system. Adnexal CRS was not associated with OS but was significantly associated with PFS using the 3-tier (HR=0.49, 95% CI: 0.263-0.914, P=0.025) and 2-tier scores (HR=0.535, 95% CI: 0.297-0.963, P=0.037). The combined score was not associated with OS but was significantly associated with PFS using the 3-tier (HR=0.348, 95% CI: 0.137-0.88, P=0.026) and 2-tier scores (HR=0.364, 95% CI: 0.148-0.896, P=0.028). No CRS system used associated with laparoscopic assessment of disease. CRS in the omentum had no significant association with platinum resistance; however, the adnexal CRS 1/2 were 3 times as likely to develop platinum resistance compared with CRS 3 (relative risk=3.94, 95% CI: 1.03-15.09, P=0.046). The CRS, when used on the omentum, adnexa, and as a combined score, was significantly associated with PFS but not with OS. Adnexal CRS 1/2 are more likely to develop platinum-resistant disease. Therefore, the use of this pathology parameter may be useful for clinical management.

Embryonal Rhabdomyosarcoma of the Ovary and Fallopian Tube

DICER1 mutations (somatic or germline) are associated with a variety of uncommon neoplasms including cervical and genitourinary embryonal rhabdomyosarcoma (ERMS). We report a primary ovarian and 2 primary fallopian tube ERMS occurring in 60-, 13-, and 14-year-olds, respectively. The 3 neoplasms exhibited a similar morphologic appearance being polypoid and containing edematous hypocellular areas and hypercellular foci composed of small cells with scant cytoplasm exhibiting rhabdomyoblastic differentiation (desmin, myogenin, myoD1 positive). There was cellular cartilage in all cases and extensive foci of anaplasia, eosinophilic globules, and bone/osteoid in 1 case each. All 3 neoplasms exhibited DICER1 mutations; in 1 of the tubal cases, the patient had a germline mutation and in the other 2 cases, the DICER1 mutations were somatic. Accompanying DICER1 “second hits” were identified in all cases. In 2 of the neoplasms, SALL4-positive glandular structures were present which we speculate may represent an unusual primitive “metaplastic” phenomenon. Our study adds to the literature on ERMS at unusual sites associated with DICER1 mutations. ERMS arising at such sites, especially when they contain cartilage or bone/osteoid, are especially likely to be associated with DICER1 mutations. Pathologists should be aware of this as these may be the sentinel neoplasms in patients with DICER1 syndrome and confirming a germline mutation can facilitate the screening of the individual and affected family members for other neoplasms which occur in this syndrome.

SOX6 Expression Is Sensitive for Peritoneal Epithelioid Malignant Mesothelioma, But Not Specific in the Differential Diagnosis With Tubo-ovarian Serous Neoplasia

Primary peritoneal malignant mesothelioma (MM) can demonstrate morphologic overlap with low-grade and high-grade tubo-ovarian serous neoplasms; it is also biologically and prognostically distinct from benign mesothelial proliferations. Currently, there is no single biomarker that can definitively distinguish these neoplasms. Sex-determining region Y box 6 (SOX6) immunohistochemistry has been recently described to differentiate pleural epithelioid MM from lung adenocarcinoma, but it has not been evaluated in the peritoneum. SOX6 immunohistochemistry was performed on 43 peritoneal epithelioid MM, 7 peritoneal biphasic MM, 5 well-differentiated papillary mesotheliomas, 5 serous borderline tumors, 29 low-grade serous carcinomas (LGSCs), 20 high-grade serous carcinomas (HGSCs), and 25 cases of peritoneal reactive mesothelial hyperplasia. Quantitative SOX6 expression in epithelioid MM (median, 100% of tumor cells) was significantly greater than in LGSC/serous borderline tumor (median, 90%; P=0.004) and HGSC (median, 45%; P=0.0001). However, when SOX6 is expression is defined as ≥10% of tumor cells, there was no significant difference in the rate of SOX6 positivity between epithelioid MM (41/43, 95%), LGSC (28/29, 97%; P=1.0), and HGSC (17/20, 85%; P=0.16). Quantitative extent of SOX6 expression in epithelioid MM was significantly greater than in biphasic MM (median, 0%; P=0.0001), well-differentiated papillary mesothelioma (median, 20%; P=0.001), and reactive mesothelial hyperplasia (median, 20%; P=0.0001), but not significantly different from flat quiescent mesothelium (median, 90%; P=0.82). SOX6 immunohistochemistry is 95% sensitive for peritoneal epithelioid MM, but is also consistently expressed in LGSC and HGSC, negating its usefulness in this common differential diagnosis. SOX6 also shows variable expression across the spectrum of reactive, benign neoplastic, and malignant mesothelial lesions of the peritoneum, and does not appear to be diagnostically useful in distinguishing benign from malignant mesothelial proliferations.

Primary Uterine Nongestational Placental Site Trophoblastic Tumor as a Distinct Entity

Uterine placental site trophoblastic tumors (PSTTs) are rare trophoblastic neoplasms, presumed to be of gestational origin. Herein, using a comprehensive morphologic, immunohistochemical, and molecular approach, we describe 5 cases of primary uterine nongestational PSTTs. The median age at presentation was 32 years (range 25 to 45). All tumors were initially expected to be of gestational origin as all were located in the uterus and all patients had a history of pregnancy (5/5, 100%). The median size of the primary uterine tumors was 6.3 cm (range 4.8 to 7.5). Three patients (3/5, 60%) had metastatic disease at presentation or revealed during initial workup (1/5 [20%] patients with lymph node metastasis only and 2/5 [40%] with distant metastases). All tumors showed similar histopathologic and immunohistochemical features to those of gestational PSTTs. The tumor cells expressed hPL in 5/5 (100%) tumors, hCG in 5/5 (100%; focal in all tumors), and GATA3 in 5/5 (100%). However, short tandem repeat (STR) genotyping did not identify any nonpatient alleles in the tumors, indicating a nongestational origin. The median progression-free survival was 18 months (range: 0 to 85) and 2/5 (40%) patients died from disease, highlighting the potential poor prognosis of this nongestational tumor. Thus, in the same way as gestational and nongestational choriocarcinomas are recognized as different entities, nongestational PSTTs could be viewed as a distinct entity from their gestational counterparts, although further investigation and more cases are needed. Furthermore, we propose recommendations for diagnosing and staging of nongestational PSTTs to improve patient stratification and management.

HPV42

Seborrheic keratosis-like lesion (SKLL) is an extremely rare, morphologically distinct lesion occurring in the cervix and vagina that differs histologically from other squamous intraepithelial lesions in these sites due to its unique morphology, including close resemblance to cutaneous seborrheic keratosis and lack of viral cytopathic effect (koilocytosis). We report a series of 17 cases, describe in detail the morphology and add to the evidence linking SKLL with low-risk human papillomavirus (LRHPV), specifically HPV42, which was detected in 13 cases; in 3 cases, an additional single HPV type (HPV6, 16, 61) was detected. In 2 of the SKLLs, a component of high-grade morphology and block-type p16 immunoreactivity were observed, prompting speculation as to the oncogenic potential of HPV42. Nineteen cases of papillary immature metaplasia, another distinctive LRHPV-associated lesion with some morphologic overlap with SKLL, were HPV42 negative. Independently, HPV42 has recently been implicated as the cause of a rare, aggressive cutaneous tumour, digital papillary adenocarcinoma (DPA), with experimental molecular data supporting the transforming capacity of this virus. These findings, along with the observation that rare anogenital squamous cell carcinomas are associated with HPV42, demonstrate the rare carcinogenic potential of this LRHPV. The association of HPV42 with these 2 unique and distinctive tumours (SKLL and DPA) also illustrates the incompletely understood diversity of HPV genotype-phenotype associations and virus-host interactions and highlights the importance of HPV typing of novel genital and cutaneous tumours.

L1-CAM in Mucinous Ovarian Carcinomas and Borderline Tumors

Mucinous ovarian carcinoma (MOC) is a rare histotype of primary ovarian carcinoma. Frequent pathogenic molecular alterations include mutations in KRAS, TP53, and overexpression of human epidermal growth factor receptor 2, but without having prognostic relevance. As L1-CAM (cell adhesion molecule) has previously shown prognostic relevance in other epithelial tumors of the female genital tract, we analyzed whether L1-CAM expression affected MOC prognosis. In addition, we investigated L1-CAM expression in mucinous borderline tumors (MBOTs) with and without adjacent MOC to identify its potential role in the pathogenesis of MOC. We examined a well-characterized collective of 39 MOCs by immunohistochemistry and compared their expression with clinicopathologic data. L1-CAM positivity was defined as any (even single-cell) positivity. Furthermore, we compared the L1-CAM expression in 20 MBOT regions adjacent to a MOC with that of 15 pure MBOTs. L1-CAM expression in MOC was significantly associated with recurrence, independent of tumor stage. Overall, 7/20 positive cases recurred versus 0/19 L1-CAM-negative cases (P=0.032), showing a significant difference in time to progression. Furthermore, the presence of at least 1 defined molecular alteration (L1-CAM, aberrant p53, or human epidermal growth factor receptor 2) was found more frequently in the MBOT regions adjacent to a MOC (14/20) than in pure MBOTs (3/15) (P=0.024). Expression of the tumor marker L1-CAM is frequent (51%) in MOC and is associated with tumor recurrence. The lack of L1-CAM may serve to characterize cases with a low risk of recurrence. Furthermore, the presence of specific molecular alterations in MBOTs is associated with adjacent carcinomas and may define potential pathways in tumor progression.

Assessment of Interobserver Agreement Among Gynecologic Pathologists Between Three-Tier Versus Binary Pattern-based Classification Systems for HPV-associated Endocervical Adenocarcinoma

The three-tier (A vs. B vs. C) pattern-based (Silva) classification system is a strong and fairly reproducible predictor of the risk of lymph node involvement and recurrence of human papillomavirus (HPV)-associated endocervical adenocarcinoma (EA). Recently, a binary pattern-based classification system has been proposed which incorporates the Silva pattern and lymphovascular invasion (LVI) to assign tumors as “low risk” or “high risk” and this may have superior prognostic significance compared with the three-tier system as well as current International Federation of Gynecology and Obstetrics (FIGO) staging of cervix-confined disease. The interobserver reproducibility of this binary system, however, is unknown. Representative slides from 59 HPV-associated EAs (1-3 slides/case) were independently reviewed by 5 gynecologic pathologists who participated in an online training module before the study. In the first review, a pattern was assigned using the three-tier system. On the second review, a “low risk” or “high risk” designation was assigned and the presence or absence of LVI was specifically documented. Interobserver agreement was assessed using Fleiss’ kappa. The binary system showed improved interobserver agreement (kappa=0.634) compared with the three-tier system (kappa=0.564), with a higher proportion of cases having agreement between at least 4/5 reviewers (86% vs. 73%). Nineteen and 8 cases showed improved and worse interobserver agreement using the binary system, respectively; the remainder showed no change. 3/5 reviewers showed no intraobserver discrepancy while the remaining 2 did in a small subset of cases (n=2 and 4, respectively). In this study, a binary pattern-based classification system showed improved interobserver agreement compared with the traditional three-tier system.

Uterine Inflammatory Myofibroblastic Tumors

Uterine inflammatory myofibroblastic tumors (IMTs) are rare mesenchymal neoplasms of uncertain malignant potential. Aside from the recently described risk stratification score, which has not been validated by other studies, and rare reports of aberrant p16 expression in malignant tumors, there are no criteria to reliably predict behavior. Herein, we evaluated the clinicopathologic features and p16 expression patterns in 30 IMTs, with genomic profiling performed in a subset (13 malignant, 3 benign). Fifteen patients had malignant IMTs, defined by extrauterine disease at diagnosis (n=5) or recurrence (n=10; median: 24 mo). Patients ranged from 8 to 65 (median: 51) years and tumors from 6 to 22 (median: 12.5) cm. In primary tumors (n=13), infiltrative borders were noted in 10, moderate/severe cytologic atypia in 9, tumor cell necrosis in 7, and lymphovascular invasion in 6, while mitoses ranged from 0 to 21 (median: 7) per 10 high-power fields. In contrast, 15 patients with benign IMTs ranged from 28 to 65 (median: 44) years, with follow-up of 18 to 114 (median: 41) months. Tumors ranged from 1.9 to 8.5 (median: 5.5) cm, 2 demonstrated infiltrative borders, and 1 had moderate cytologic atypia. No other high-risk histologic features were observed. Application of the previously described clinicopathologic risk stratification score in all primary IMTs with complete data (n=18) classified 8 as high-risk (all malignant), 8 as intermediate-risk (3 malignant, 5 benign), and 2 as low-risk (benign). p16 was aberrant in all malignant IMTs, with <1% expression noted in 10, overexpression (>90%) in 4, and subclonal loss in 1; all benign tumors had patchy staining (20% to 80%; median 50%). Molecular analysis detected CDKN2A deletions in 8 of 9 tumors with <1% p16 expression, while the other harbored a TERT promoter mutation. TERT promoter mutations were also identified in 2 of 3 IMTs with p16 overexpression. Neither of these alterations was detected in the 3 sequenced benign IMTs. Thus, we recommend performing p16 on all uterine IMTs, which, combined with the risk stratification score, is a promising and cost-effective tool for predicting CDKN2A status and outcome in these patients. It may be particularly useful for tumors with incomplete information for risk stratification (ie, morcellated tumors) and for further stratifying intermediate-risk IMTs when sequencing is unavailable.

Uterine Leiomyosarcoma Associated With Perivascular Epithelioid Cell Tumor

Perivascular epithelioid cell tumor (PEComa) is a mesenchymal tumor thought to originate from perivascular epithelioid cells (PECs). The normal counterpart to PEC, however, has not been identified in any human organ, and the debate as to whether PEComa is related to smooth muscle tumors has persisted for many years. The current series characterizes 4 cases of uterine leiomyosarcoma (LMS) coexisting with PEComas. All cases exhibited an abrupt transition from the LMS to PEComa components. The LMS component displayed typical spindled morphology and fascicular growth pattern and was diffusely positive for desmin and smooth muscle myosin heavy chain, completely negative for HMB-45 and Melan A, and either negative or had focal/weak expression of cathepsin K and GPNMB. In contrast, the PEComa tumor cells in case 1 contained glycogen or lipid-distended cytoplasm with a foamy appearance (low grade), and in cases 2, 3, and 4, they displayed a similar morphology characterized by epithelioid cells with eosinophilic and granular cytoplasm and high-grade nuclear atypia. Different from the LMS component, the epithelioid PEComa cells in all cases were focally positive for HMB-45, and diffusely immunoreactive for cathepsin K and GPNMB. Melan A was focally positive in cases 1 and 3. Loss of fumarate hydratase expression (case 1) and RB1 expression (cases 2, 3, 4) was identified in both LMS and PEComa components, indicating that they are clonally related. In addition, both components showed an identical TP53 p.R196* somatic mutation and complete loss of p53 and ATRX expression in case 2 and complete loss of p53 expression in case 3. We hypothesize that LMSs containing smooth muscle progenitor cells may give rise to divergent, lineage-specific PEComatous lesions through differentiation or dedifferentiation. While we do not dispute the recognition of PEComas as a distinct entity, we advocate the hypothesis that modified smooth muscle cells represent the origin of a subset of PEComas, and our case series provides evidence to suggest this theory.

Female Adnexal Tumor of Probable Wolffian Origin (Wolffian Tumor)

Wolffian tumor and its nosologic relative, the recently defined STK11 adnexal tumor are rare neoplasms thought to arise from mesonephric remnants. These tumors typically arise in the broad ligament, fallopian tube, and ovarian hilum and although most are associated with a good prognosis, up to 50% of STK11 adnexal tumors demonstrate aggressive clinical behavior. The chief differential diagnoses include endometrioid adenocarcinoma and sex cord stromal tumors. However, the morphologic and immunohistochemical features of these tumors exhibit considerable overlap with peritoneal mesothelioma. To fully characterize their immunophenotypic signature, we examined a total of 21 cases (18 Wolffian and 3 STK11 adnexal tumors) with standard markers used in the diagnosis of mesothelioma. Morphologic and immunohistochemical (IHC) features were reviewed and additional IHC performed for cases with available material. Patient age ranged from 25 to 73 (mean: 51) years. Sites included adnexa/broad ligament (6, 28%), paratubal (5, 24%), ovary/paraovarian (5, 24%), tubal (intraluminal) (2, 9.5%), pelvis (2, 9.5%), and liver (1, 5%). The mean tumor size was 9.3 cm (range: 0.2 to 22 cm). The histomorphology in most cases (14/21, 66%) consisted of tubular to solid sheets of neoplastic cells lined by columnar to cuboidal cells containing uniform round to oval nuclei. Compressed tubules with slit-like lumens and sieve-like pattern were also seen in at least 7 (33%) cases. Three cases demonstrated interanastomosing cords and trabeculae of epithelioid cells with cribriform and microacinar patterns growing within prominent myxoid stroma as described in STK11 adnexal tumors. In the cases with available IHC for 3 mesothelial markers (calretinin, WT1, D2-40), 55.5% (5 of 9) showed reactivity with all 3 markers. In cases with at least 2 available mesothelial markers, 69% (11/16) were positive for 2 markers (mostly calretinin and WT1). Claudin-4, MOC31, and BER-EP4 were negative in most cases tested (78% [7/9], 71.4% [5/7], and 100% [6/6], respectively). Given the resemblance to mesothelioma, there was initial strong consideration and/or actual misdiagnosis of mesothelioma in 3 cases (14%). In summary, the morphologic and immunohistochemical features of Wolffian tumor and its recently defined relative, STK11 adnexal tumor, can lead to misdiagnosis of mesothelioma, particularly when encountered in the disseminated or metastatic setting. Wolffian tumor and STK11 adnexal tumor should be considered in the differential diagnosis of all pelvic and peritoneal mesotheliomas.

Cervical Adenoid Basal Carcinoma With High-grade Squamous Component

Adenoid basal carcinoma (ABC) is a rare clinically indolent human papillomavirus–associated cervical neoplasm with uniformly bland morphology which in pure form does not metastasize. Many cases co-exist with a human papillomavirus–associated high-grade squamous intraepithelial lesion (HSIL) or squamous cell carcinoma (SCC). The ABC and high-grade squamous components may be clearly separate, albeit intermingled, and when the high-grade squamous component is invasive, the tumor is designated a mixed carcinoma, with clinical behavior determined by the non-ABC component. In other cases, discrete nests of high-grade atypical squamous cells are intimately admixed and incorporated within the ABC. These are more difficult to classify but are also usually reported as mixed carcinomas. Herein, we report a series of 9 cases of ABC in patients aged 33 to 89 years (mean age: 63 y) with a high-grade squamous component. In 7 cases, the high-grade squamous cells partly replaced and expanded the nests of ABC, sometimes with a residual cuff of ABC cells, while in the other 2 cases the ABC and SCC were clearly separate. We propose that the aforementioned 7 cases represent colonization of ABC by HSIL rather than mixed carcinomas; as far as we are aware, this concept has not been proposed before. In all cases which we feel represent colonization of ABC by HSIL, the tumors were confined to the cervix (stages IA1 [3 tumors], IA2 [2 tumors], IB1 [2 tumors]) and follow-up was unremarkable with no evidence of metastasis. One case with separate components of ABC and SCC was stage IVA at diagnosis and the patient died of disease. The other was stage IB1 at diagnosis and the patient died of unrelated causes at 13 months. We discuss the clinical implications of distinguishing true mixed carcinomas from colonization of ABC by HSIL and provide an approach to diagnosis. We also report a unique case of colonization of so-called cervical ectopic prostatic tissue by HSIL.

Central Pathology Review of Endometrial Hyperplasia and Adenocarcinoma Before and After Treatment With the Levonorgestrel Intrauterine Device–Results From the feMMe Phase 2 Randomized Clinical Trial

Distinguishing endometrial hyperplasia from endometrial adenocarcinoma remains a histopathologic challenge. Several retrospective studies have reported high interobserver variability when assessing the progestin-naive endometrium, while only one study has assessed interobserver variability of postprogestin endometrial biopsies. This study quantified the interobserver variability between trial site pathologists and central pathology review of endometrial specimens taken before treatment with the levonorgestrel intrauterine device (LNG-IUD), 3 months and 6 months post-treatment as part of the feMMe phase 2 randomized clinical trial (NCT01686126). Interobserver agreement was 73% (105/143, κ=0.50) at baseline, 80% (107/134, κ=0.72) at 3 months and 77% (98/127, κ=0.64) at 6 months post-LNG-IUD treatment. Overall, 42% (45/107) site-reported diagnoses of endometrial hyperplasia and 13% (21/161) site-reported diagnoses of endometrial adenocarcinoma were discordant. Site-reported diagnoses were upgraded to higher risk pathology on central review for 77% (72/94) discordant cases. This study confirms the high rate of interobserver variability when diagnosing endometrial hyperplasia or endometrial adenocarcinoma both before and after progestin treatment in specimens collected as part of a clinical trial. It emphasizes the value of confirming diagnosis by a gynecologic pathologist and comparing specimens from the progestin-treated endometrium with the pretreatment biopsy. This study highlights the importance of central pathology review for clinical trial reporting and when deciding on treatment options and assessing response, particularly in the context of progestin treatment.

Well-differentiated Sertoli-Leydig Cell Tumors (SLCTs) Are Not Associated With DICER1 Pathogenic Variants and Represent a Different Tumor Type to Moderately and Poorly Differentiated SLCTs

Sertoli-Leydig cell tumors (SLCTs) are uncommon ovarian sex cord-stromal neoplasms which are currently classified into well, moderately, and poorly differentiated and retiform types. Well-differentiated SLCT is the least common and typically occurs in pure form, whereas moderately and poorly differentiated and retiform types often comprise a morphologic spectrum with an admixture of all 3. DICER1 pathogenic variants are very common in SLCTs but, as far as we are aware, have not been reported in well-differentiated neoplasms, although the number of cases studied is small due to the rarity of this neoplasm. We undertook DICER1 molecular testing in a cohort of 18 well-differentiated SLCTs and show all these to be DICER1 wild-type. None of the cases harbored the p.FOXL2 C134W hotspot mutation. Based upon the DICER1 molecular results, together with morphologic observations, we propose that well-differentiated SLCT is an unrelated neoplasm to the more common moderately/poorly differentiated and retiform SLCTs and is a fundamentally distinct and unrelated tumor type within the ovarian sex cord-stromal tumor family. The implications for tumor nomenclature and recommendations for future tumor classification are discussed within the context of tumors collectively known as SLCTs.

Histologic and Molecular Type Changes in Endometrial Cancer Recurrences in Comparison With Their Corresponding Primary Tumors

In this study, molecular alterations in endometrial carcinoma (EC) recurrences were analyzed. We aimed to identify genes implicated in tumor progression and to evaluate whether histologic and molecular type shifting occurs in recurrences. Thus, we analyzed 50 samples corresponding to 24 primary ECs (15 low-grade endometrioid endometrial carcinomas [LG-EECs] and 9 high-grade endometrial carcinomas) and their corresponding 26 recurrences. These were studied by immunohistochemistry, next-generation sequencing, and MLH1 promoter methylation. We observed shared mutations in all primary tumors and their recurrences, indicating a clonal relationship between both lesions. Most morphologic and molecular changes associated with progression were found in LG-EEC. In this group, 6 patients (40%) presented additional mutations in the recurrence. These mutations more frequently affected genes of the PI3K/AKT/PTEN pathway, implicating this pathway not only in tumor initiation but also in progression. In addition, 2 patients (13%) in which the primary tumor belonged to the nonspecific molecular profile subtype, shifted to the mismatch repair deficient (MMRd) subtype after the acquisition of MLH1 promoter methylation in the recurrence lesions. In 3 patients (20%) with MMRd, there was a change from LG-EEC to G3-EEC. One TP53-mutated LG-EEC transformed into an undifferentiated carcinoma in a mediastinal lymph node metastasis after losing the expression of SMARCA2 while preserving SMARCA4 and SMARCB1. Morphologic and molecular changes in EC recurrences, especially dedifferentiation and the acquisition of MMRd, should be considered for a correct diagnosis and treatment. MMRd should be tested in metastatic lesions, if available, in patients with primary tumors reported to be of a molecular subtype different from MMRd.

Mismatch Repair Deficiency in Ovarian Carcinoma

Mismatch repair deficiency (MMRD) is involved in the initiation of both hereditary and sporadic tumors. MMRD has been extensively studied in colorectal cancer and endometrial cancer, but not so in other tumors, such as ovarian carcinoma. We have determined the expression of mismatch repair proteins in a large cohort of 502 early-stage epithelial ovarian carcinoma entailing all the 5 main subtypes: high-grade serous carcinoma, endometrioid ovarian carcinoma (EOC), clear cell carcinoma (CCC), mucinous carcinoma, and low-grade serous carcinoma. We studied the association of MMRD with clinicopathologic and immunohistochemical features, including tumor-infiltrating lymphocytes in EOC, the histologic type in which MMRD is most frequent. In addition, MLH1 promoter methylation status and massive parallel sequencing were used to evaluate the proportion of sporadic and Lynch syndrome–associated tumors, and the most frequently mutated genes in MMRD EOCs. MMRD occurred only in endometriosis-associated histologic types, and it was much more frequent in EOC (18%) than in CCC (2%). The most frequent immunohistochemical pattern was loss of MLH1/PMS2, and in this group, 80% of the cases were sporadic and secondary to MLH1 promoter hypermethylation. The presence of somatic mutations in mismatch repair genes was the other mechanism of MMRD in sporadic tumors. In this series, the minimum estimated frequency of Lynch syndrome was 35% and it was due to germline mutations in MLH1, MSH2, and MSH6. ARID1A, PTEN, KTM2B, and PIK3CA were the most common mutated genes in this series. Interestingly, possible actionable mutations in ERRB2 were found in 5 tumors, but no TP53 mutations were detected. MMRD was associated with younger age and increased tumor-infiltrating lymphocytes. Universal screening in EOC and mixed EOC/CCC is recommended for the high frequency of MMRD detected; however, for CCC, additional clinical and pathologic criteria should be evaluated to help select cases for analysis.

Clinicopathologic, Immunohistochemical, and Molecular Characteristics of Ovarian Serous Carcinoma With Mixed Morphologic Features of High-grade and Low-grade Serous Carcinoma

Despite the current classification of high-grade serous carcinoma (HGSCA) and low-grade serous carcinoma (LGSCA) as mutually exclusive diseases based on morphology and molecular pathogenesis, cases with mixed morphologic features of HGSCA and LGSCA have been reported. Herein we assess the clinicopathologic, immunohistochemical (IHC), and molecular genetic characteristics of a group of these cases, which we termed indeterminate grade serous carcinoma (IGSCA) in comparison with groups of HGSCA and LGSCA. Using the World Health Organization (WHO) classification criteria, we selected 27 LGSCA and 19 IGSCA for detailed morphologic study. Thirteen classic HGSCA, 19 classic LGSCA, and 19 IGSCA were selected for p53 and BRAF V600E IHC and molecular genetic testing by next-generation sequencing. IGSCA showed the architectural patterns of invasion of LGSCA, but with higher grade nuclear features focally and a mitotic index intermediate between LGSCA and HGSCA. Few cases in the IGSCA group showed mutant TP53 by IHC or sequencing (4/18, 22.2%), 1 case had mutant BRAF non-V600E by sequencing, and 1 had an NRAS mutation. When present, the mutations were identical in the low-grade and high-grade areas. The IGSCA group had a long-term survival similar to the classic HGSCA group. IGSCA with mixed morphologic features of HGSCA and LGSCA is a rare and potentially clinically aggressive variant of serous carcinoma. Their distinct morphologic, but heterogenous molecular features, including low frequency of TP53 and BRAF mutations suggest that these rare tumors may have a different pathogenesis pathway compared with classic HGSCA and classic LGSCA.

Specific Pathology Features Enrich Selection of Endometrial Carcinomas for POLE Testing

Identification of ultramutated/POLE-mutated endometrial carcinomas (POLE M ECs) has important implications given its association with better prognosis. However, POLE mutation testing is not widely available. Our objective was to evaluate POLE M ECs versus POLE wild-type (POLE WT) ECs, within a cohort of consultation cases with features suggestive of an ultramutated phenotype. Consultation cases of EC that had undergone POLE hotspot mutation testing over a 3.5-year period were included. Tumor morphology and immunohistochemistry were reviewed for both groups. Chi-square test and t test were used for statistical analysis. Of 25 consultation cases, 12 harbored a POLE mutation (48%) and 13 were wild-type (52%). Patients with POLE M ECs were younger (59 vs. 71.3 y; P=0.01). Ambiguous histomorphology (5/12 vs. 1/13; P=0.04) and the presence of more than rare bizarre nuclei (8/12 vs. 2/12; P=0.01) differed significantly between POLE M and POLE WT ECs, respectively. In the POLE M group, one case (1/12) demonstrated PMS2 loss, and one (1/12) showed subclonal MLH1/PMS2 loss. Among POLE WT ECs, 3/13 (23%) showed MLH1/PMS2 loss. p53 was subclonally overexpressed in 4/10 POLE M and 1/13 POLE WT cases (P=0.06). Mutant p53 patterns were seen in 1/10 POLE M versus 6/13 of POLE WT ECs, respectively (P=0.06). Within our cohort, the specificity of ambiguous histomorphology, bizarre nuclei, subclonal biomarker expression, and marked tumor-infiltrating lymphocytes for POLE M EC was 83%, 80%, 80%, and 71%, respectively. Where universal POLE testing is not available, these data suggest that morphologic screening (particularly ambiguous histomorphology and the presence of more than rare bizarre nuclei) can be useful for selective enrichment of ECs for POLE testing.

p16 Positive Histologically Bland Squamous Metaplasia of the Cervix

With increasing use of p16 immunohistochemistry (IHC) in diagnosis of premalignant lesions of cervix, we occasionally encounter p16 positivity in squamous metaplasia that lacks morphologic characteristics of “atypical squamous metaplasia” or of squamous intraepithelial lesion (SIL). Our study aims to investigate if transcriptionally active human papilloma virus (HPV) can be identified in such foci and if they have any relationship with squamo-columnar junction (SCJ) cells. Twenty-two cases of cervical specimens with at least a focus of p16 positive bland squamous metaplasia, were selected. HPV E6/E7 mRNA in situ hybridization followed by IHC for CK7 (SCJ biomarker), Ki67, and HPV16 E2, were performed. Follow-up information was obtained. Four cases were excluded due to insufficient tissue. Of the final 18 cases, HPV E6/E7 mRNA in situ hybridization was positive in all. Nine cases showed positivity in >50% cells and the epithelial thickness involved was ≥lower two-thirds in 13 cases. Of the further evaluable 15 cases, CK7 was positive in 14, Ki67 was positive in 10, and HPV16 E2 was negative in all. Concomitant high-grade squamous intraepithelial lesion was identified in 10 cases. On follow-up (duration: 1 to 19 mo), 6 patients showed histologic high-grade squamous intraepithelial lesion. Our study demonstrates that p16 positivity in squamous metaplasia of cervix is associated with the presence of transcriptionally active high-risk HPV even when there are no clear morphologic features of dysplasia. Our results suggest that these lesions are early SILs or SILs that are not yet morphologically evident, most of which arise from SCJ and should be closely followed.

Serous Borderline Tumors of the Testis and Paratestis

Serous borderline tumors of the testis and paratestis are rare, and experience with these neoplasms is limited. We report a series of 19 tumors, emphasizing their morphologic spectrum and clinical behavior. Eighteen tumors (95%) had conventional serous borderline tumor morphology identical to ovarian serous borderline tumors, and 1 case (5%) had a pattern resembling the epithelial subtype of noninvasive implants of serous borderline tumor. A component of micropapillary serous borderline tumor was present in 6 tumors (31%), including 1 that was exclusively micropapillary. Five tumors (26%) had associated autoimplants. Microinvasion was identified in 4 tumors (21%). One tumor had associated low-grade serous carcinoma, and 1 tumor had associated high-grade serous carcinoma. Immunohistochemical stains demonstrated diffuse expression of PAX8 in 12 of 12 (100%) cases. Estrogen receptor was diffusely positive in 11 of 12 (92%) cases and progesterone receptor was positive in 8 of 9 (89%) cases. D2-40 was negative in 7 of 9 (78%) cases and calretinin was negative in 11 of 11 cases (100%). Clinical follow-up data were available in 9 patients (47%) with pure serous borderline tumors, of which 4 had micropapillary features (44%), 3 had microinvasion (33%), and 2 had autoimplants (22%). None of these 9 patients experienced adverse outcomes related to serous borderline tumor over the follow-up period (mean: 94 mo, median: 85 mo, range: 17 to 204 mo). Serous borderline tumors of the testis and paratestis are identical morphologically to their ovarian counterparts and can be associated with similar histologic phenomena (microinvasion, autoimplants, and micropapillary features). Although they can develop associated serous carcinoma, we conclude that serous borderline tumors of the testis and paratestis (when pure) appear to show indolent behavior.

Embryoid Bodies and Related Proliferations in Ovarian Germ Cell Tumors

We investigated the frequency and associated pathology of embryoid bodies in ovarian tumors by evaluating neoplasms in which they are known to occur: 100 immature teratomas, 125 malignant mixed germ cell tumors, and 6 polyembryomas. Three immature teratomas contained a single relatively well-formed embryoid body, whereas these and 11 others showed foci we categorized as embryoid body remnants consisting of microscopic aggregates of embryonal or yolk sac-type epithelium associated with spaces consistent with yolk sac or amniotic cavity but lacking a classic embryoid body structure. Teratomas with these foci were all high grade. A well-formed embryoid body was found in only 1 malignant mixed tumor, but embryoid body remnants were present in 25%, invariably associated with foci of immature teratoma (100%) and often with yolk sac tumor (97%), embryonal carcinoma (35%), or both (32%). These foci usually took the form of round to oval aggregates, often well-circumscribed, for which the term “polyembryoma background” has been proposed. The polyembryomas were typically grossly hemorrhagic and occurred in patients from 9 to 43 years of age. The embryoid bodies in them generally grew in lobules within an edematous to occasionally myxoid stroma. Four tumors contained liver-like cells, 4 numerous glands likely recapitulating the allantois, 3 syncytiotrophoblast cells, 2 prominent cysts, and 2 striking vascular proliferations. This study indicates that (1) typical embryoid bodies are rare in immature teratomas but about 14% of them have embryoid body remnants. (2) Embryoid body remnants are seen in 25% of malignant mixed germ cell tumors with a teratomatous component and often proliferate to form yolk sac tumor and embryonal carcinoma. (3) Well-formed embryoid bodies growing in a confluent manner (polyembryoma) are rare, and minor foci of teratoma, yolk sac tumor, or embryonal carcinoma are almost always present, indicating that these are fundamentally malignant mixed germ cell tumors but the polyembryoma component is dominant and distinctive which, in our opinion, justifies its own nomenclature. (4) Embryoid bodies are not a feature of other germ cell tumors.

Ovarian Intermediate Trophoblastic Tumors

Trophoblastic neoplasms involving the ovary are uncommon and include gestational tumors, which are either metastatic from the uterus or ectopic and nongestational tumors, which include those of germ cell type/origin and somatic tumors with trophoblastic differentiation; in all these types, most are pure choriocarcinoma. Intermediate trophoblastic tumors, which include placental site trophoblastic tumor (PSTT) and epithelioid trophoblastic tumor (ETT), are rare in the ovary, with most assumed to be gestational; this is the only category formally recognized in 2014 World Health Organization (WHO) classification, likely due to few well-documented nongestational examples. We report the clinicopathologic features of 6 ovarian intermediate trophoblastic tumors, including 3 PSTTs, 2 ETTs, and 1 ETT with choriocarcinomatous differentiation. DNA-based short tandem repeat genotyping identified 4 of these as nongestational (3 PSTTs and 1 ETT), as evidenced by sharing of alleles between tumor and normal tissue at all informative loci. Interestingly, all 3 of the nongestational PSTTs coexisted with mature cystic teratoma. The remaining 2 tumors (1 ETT and 1 ETT with some choriocarcinomatous differentiation) were gestational (likely ectopic due to lack of evidence of a uterine tumor), as evidenced by the presence of both maternal and novel/nonmaternal alleles at informative loci in tumor compared with normal tissue. It is important to recognize a distinct category of primary ovarian nongestational intermediate trophoblastic tumors of germ cell type/origin, including PSTT and ETT, in classification systems to guide clinical management, as gestational and nongestational tumors have different genetic origins and may require different therapy. Genotyping is useful for classification as nongestational versus gestational, particularly as traditional clinicopathologic findings cannot always predict the nature of a trophoblastic tumor.

NKX3.1 and Prostein Expression in Testicular Tissue and Sex Cord-stromal Tumors

Prostate cancer is well known to metastasize to the testis and is not an uncommon finding on castration performed for advanced disease. Although germ cell tumors make up the majority of testis neoplasms, there are more rare tumors, such as rete testis adenocarcinoma, that can mimic metastatic disease. NKX3.1 and prostein (P501S) are antibodies highly specific for prostate origin. Relatively little is known of the expression of these markers in testicular tissue. We investigated the expression of NKX3.1 and P501S in testicular tissues, sex cord-stromal tumors, germ cell tumors, and rete testis adenocarcinoma. We found strong diffuse nuclear staining for NKX3.1 in Sertoli cells of the testis. Expression of NKX3.1 was seen in 0/3 ovarian Sertoli cell tumors, 1/4 testicular Sertoli cell tumors, and in the Sertoli cell component of 1/12 ovarian Sertoli-Leydig cell tumors. We found moderate, diffuse cytoplasmic positivity for P501S in rete testis epithelium and in testicular Leydig cells. P501S also highlighted Leydig cells in 9/12 Sertoli-Leydig cell tumors of the ovary. Two of 3 Leydig cell tumors of the testis showed weak to moderate, diffuse cytoplasmic staining for P501S. All cases of embryonal carcinoma and pure seminoma were negative for both NKX3.1 and P501S. One case of rete testis adenocarcinoma showed patchy positivity for both NKX3.1 and P501S. In conclusion, NKX3.1 shows routine expression in Sertoli cells and P501S shows routine expression in Leydig cells and rete testis epithelium. In addition, these markers can be positive in sex cord-stromal tumors and rete testis adenocarcinoma.

The Frequency and Prognostic Significance of the Histologic Type in Early-stage Ovarian Carcinoma

The frequency and prognostic significance of the histologic type in early-stage ovarian cancer (OC) is not as well established as in advanced stages. In addition, histologic typing based only on morphologic features may be difficult, especially in high-grade tumors. In this study, we have analyzed a prospective cohort of 502 early-stage OCs to investigate their frequency, immunohistochemical characteristics, and survival of the 5 main histologic types. Histotype was assigned according to not only the morphologic features but also according to the expression pattern of WT1, p53, Napsin A, and progesterone receptors. In addition, an extended panel including p16, β-catenin, HER2, Arid1A, HINF1B, CK7, CDX2, and CK20 was used to refine the diagnosis in difficult cases. In this series, the frequency of the 5 major histologic types was as follows: endometrioid carcinoma, 32.7%; clear cell carcinoma, 25.1%; high-grade serous carcinoma (HGSC), 24.7%; mucinous carcinoma, 10.2%; low-grade serous carcinoma, 4.6%; and others, 2.8%. The combination of morphology and immunohistochemistry allowed the reclassification of 23% of OCs. The lowest concordance was found between samples initially diagnosed as endometrioid, but finally classified as high-grade serous tumors (22% error rate). Endometrioid carcinoma was the most favorable histologic type, whereas HGSC and low-grade serous carcinoma had the worst prognosis. Clear cell carcinoma with abnormal p53 immunostaining pattern also had poor prognosis. Although histologic grade was not a prognostic factor among early-stage endometrioid OCs, distinction between grade 3 endometrioid OC and HGSC is recommended, taking into account differences in prognosis and molecular alterations that can guide different treatments.

GTF2A1-NCOA2-Associated Uterine Tumor Resembling Ovarian Sex Cord Tumor (UTROSCT) Shows Focal Rhabdoid Morphology and Aggressive Behavior

Dysgerminoma of the Ovary

One-hundred fourty pure dysgerminomas were evaluated with particular focus on the microscopic features as seen in 125 cases with available slides. The patients ranged from 8 to 59 years of age (mean, 24.1 y). The tumors, bilateral in 4% of the cases and with a mean tumor diameter of 13 cm, were typically soft, lobulated, homogeneous, and creamy white to tan to yellow but necrosis was found in 13%, hemorrhage in 20%, and focal cystic change in 15%. On microscopic examination, the patterns and other notable features encountered, including their frequency, were as follows: an alveolar pattern resulting from delicate fibrovascular septa (51%), diffuse (33%), macronodular (14%), insular (26%), cords (28%), solid tubular (17%), microspaces (sometimes simulating glands) (12%), follicle-like spaces (5%), prominent fibrous bands (65%), stromal edema (56%), stromal luteinization (9%), granulomatous infiltrate (46%), lymphocytic infiltrate (100%), Langhans cell type giant cells (35%), syncytiotrophoblast giant cells (6%), prominent population of cells with pale to clear cytoplasm (73%), cells with amphophilic to eosinophilic cytoplasm (53%) and vacuolated occasionally signet ring-like cells (7%). Various constellations of the above findings often resulted in an appearance different from that usually portrayed in the literature and certain tumors of very different nature being in the differential such as undifferentiated carcinoma not otherwise specified, small cell carcinoma of hypercalcemic type, and malignant lymphoma. The correct diagnosis can be arrived at by considering the usual relative youth of the patient, often rather characteristic gross features, and most crucially careful attention to the microscopic features and awareness of variant morphologic findings. Those that are particularly problematic based on this study are diffuse growth with inconspicuous fibrovascular septa, macronodules, cords, solid tubular formations, spaces ranging from small to large, and mimicking glands or follicles, prominent fibrous to edematous stroma, and cells with amphophilic to eosinophilic cytoplasm. According to the degree of difficulty and confidence of the interpreter, well-known immunohistochemical features of dysgerminoma, which largely differ from those of other neoplasms in the differential, will aid if felt indicated.

A Distinctive Adnexal (Usually Paratubal) Neoplasm Often Associated With Peutz-Jeghers Syndrome and Characterized by STK11 Alterations (STK11 Adnexal Tumor)

We describe 22 examples of a novel, usually paratubal, adnexal tumor associated with Peutz-Jeghers syndrome in nearly 50% of cases that harbored STK11 alterations in all tested (n=21). The patients ranged from 17 to 66 years (median=39 y) and the tumors from 4.5 to 25.5 cm (median=11 cm). Most (n=18) were paratubal, with metastases noted in 11/22 (50%) and recurrences in 12/15 (80%). Morphologically, they were characterized by interanastomosing cords and trabeculae of predominantly epithelioid cells, set in a variably prominent myxoid to focally edematous stroma, that often merged to form tubular, cystic, cribriform, and microacinar formations, reminiscent of salivary gland-type tumors. The tumor cells were uniformly atypical, often with prominent nucleoli and a variable mitotic index (median=9/10 HPFs). The tumors were usually positive to a variable extent for epithelial (CAM5.2, AE1/AE3, cytokeratin 7), sex cord (calretinin, inhibin, WT1), and mesothelial (calretinin, D2-40) markers, as well as hormone receptors. PAX8, SF1, and GATA-3 were rarely positive, while claudin-4, FOXL2, and TTF-1 were consistently negative. All sequenced tumors (n=21) harbored alterations in STK11, often with a loss of heterozygosity event. There were no other recurrently mutated genes. Recurrent copy number alterations included loss of 1p and 11q, and gain of 1q, 15q, and 15p. Despite an extensive morphologic, immunohistochemical, and molecular evaluation, we are unable to determine with certainty the histogenesis of this unique tumor. Wolffian, sex cord stromal, epithelial, and mesothelial origins were considered. We propose the term STK11 adnexal tumor to describe this novel entity and emphasize the importance of genetic counseling in these patients as a significant number of neoplasms occur in association with Peutz-Jeghers syndrome.

Malignant Mixed Germ Cell Tumors of the Ovary

One hundred malignant mixed germ cell tumors of the ovary that occurred in patients 3 to 55 years (mean: 20 y) of age are described. The clinical presentation was usually that of any highly malignant tumor of the ovary (abdominal pain and distension), but rarely (3 cases) endocrine manifestations were present. The tumors were usually unilateral (96%), ranged from 4 to 38 cm (mean: 16 cm), and were uniformly solid or, more often, solid and cystic; occasionally the typical appearance of dysgerminoma could be appreciated. The most common tumor type was yolk sac tumor (91%), followed by dysgerminoma (61%), immature teratoma (58%), embryonal carcinoma (38%), and choriocarcinoma (11%). A variety of admixtures were encountered; dysgerminoma and yolk sac tumor was the most common combination (25% of the tumors) with the 2 components often being sharply demarcated. Immature teratoma and yolk sac tumor was the next most common pairing (20%) followed by yolk sac tumor and embryonal carcinoma, with or without immature teratoma (16%). Tumors with a choriocarcinoma component had the most varied combinations of tumor types. Embryoid bodies were seen in 21% of the tumors, most often as fragmented forms arranged in a nodular manner with yolk sac tumor and/or embryonal carcinoma; uncommonly they occurred singly or in clusters. Numerous confluent well-formed embryoid bodies (polyembryoma) were prominent in 2 tumors. Three tumors had a focal diffuse embryoma pattern. The specific tumor types showed the known diverse spectrum of microscopic appearances, but the frequent haphazard arrangement of 2 or more subtypes often resulted in complex morphology. Overgrowth of another neoplastic component, most often primitive neuroectodermal tumor, occurred in 10% of the tumors further complicating the histologic picture. This is the largest series of ovarian malignant mixed germ cell tumors reported and details their characteristics including associations of their subtypes and the frequent apparent role of embryoid bodies in giving rise to yolk sac tumor and embryonal carcinoma components.

Rare DICER1 and Absent FOXL2 Mutations Characterize Ovarian Juvenile Granulosa Cell Tumors

FOXL2 somatic mutation occurs in a high percentage of ovarian adult granulosa cell tumors and DICER1 mutations in a high proportion of Sertoli-Leydig cell tumors. These mutations have only been studied in a limited number of juvenile granulosa cell tumors (JGCTs), and their occurrence and frequency in these neoplasms is controversial. We aimed to determine the frequency of FOXL2 and DICER1 mutations in a large cohort of 50 JGCTs, and to evaluate the prognostic impact of these mutations. A FOXL2 hotspot mutation was found in 2/50 JGCTs. Review of these 2 cases reclassified them as adult granulosa cell tumors. Thus, FOXL2 mutation was absent from our large cohort of JGCTs. DICER1 mutations in the RNase IIIb domain were found in 4 cases. After review of the mutated cases, 1 was reclassified as a gynandroblastoma with a prominent JGCT component. Thus, DICER1 mutations were detected in 3/47 (6%) of pathologically confirmed JGCTs. Our results show that FOXL2 mutations are not present in JGCT, whereas a small percentage of these neoplasms exhibit DICER1 mutations.

Sertoli-Leydig Cell Tumors of the Ovary With Follicular Differentiation Often Resembling Juvenile Granulosa Cell Tumor

Thirty-eight ovarian Sertoli-Leydig cell tumors that contained follicles are described; in 33 of them follicles imparted a microscopic appearance resembling that of the juvenile granulosa cell tumor. The average age of the patients (28 y), frequency of androgenic manifestations (40%), and dominant histopathologic features were all typical of Sertoli-Leydig cell tumor, mostly (80%) of intermediate differentiation. The remaining tumors were poorly differentiated; none were well differentiated. The follicles that mimicked juvenile granulosa cell tumor accounted for ∼5% to 40% of the tumor volume. They typically arose out of the characteristic lobules seen in Sertoli-Leydig cell tumors of intermediate differentiation. There appeared to be a gradual loosening of the stroma imparting a pale appearance to the lobules and on that background follicles emerged. The follicles were mostly relatively regular and round to oval with basophilic or eosinophilic secretion and when fully formed perfectly mimicked juvenile granulosa cell morphology. In 18 of these cases, and 5 others, follicles were present that had a nonspecific morphology and had a random, nonlobule-associated distribution. The presence of a juvenile granulosa-like appearance often raised consideration of the diagnosis of a sex cord-stromal tumor of mixed forms (so-called gynandroblastoma) but a multifocal origin within lobules of otherwise typical Sertoli-Leydig cell tumors, and overall tumor characteristics indicates aberrant differentiation within the latter tumor of a nature only sporadically noted in the prior literature. Such neoplasms should, in our opinion, not be placed in the grouping of a sex cord-stromal tumor of mixed forms but rather in the Sertoli-Leydig category.

Molecular Characterization of Neuroendocrine Carcinomas of the Endometrium

High-grade neuroendocrine carcinomas (NEC) of the endometrium are rare and account for <1% of all endometrial carcinomas. Both small cell neuroendocrine carcinoma (SCNEC) and large cell neuroendocrine carcinoma (LCNEC) morphologies have been reported. Little is known regarding the molecular features of endometrial NEC including how they compare to pulmonary NEC (the most common site for these neoplasms) and the more common endometrial carcinoma histotypes. In this study, we investigated the molecular alterations in a series of endometrial NEC using a targeted next generation sequencing panel (Oncopanel). Fourteen NEC were sequenced; pure NEC (n=4) and mixed (n=10) with endometrioid adenocarcinoma (n=9) or carcinosarcoma (n=1). The NEC components of mixed tumors comprised LCNEC (n=6) and SCNEC (n=4). The 4 pure NEC comprised LCNEC (n=2) and SCNEC (n=2). Molecular analysis classified tumors into the 4 The Cancer Genome Atlas groups: (1) POLE-mutated/ultramutated (1/14; 7%), (2) microsatellite instability/hypermutated (6/14; 43%), (3) TP53 mutated/copy number high (2/14; 14%), or (4) no specific molecular profile (5/14; 36%). Overall, 50% of cases were ultramutated or hypermutated. In 8 cases of mixed carcinomas, the different histologic components were macrodissected and separately sequenced; molecular alterations were nearly identical among the 2 components, with the non-NEC component harboring slightly increased tumor mutational burden. Only 2 carcinomas (both with pure SCNEC morphology) had a molecular profile that would be expected in typical pulmonary SCNEC (RB1 deletion and TP53 mutations). Our findings, similar to data from NECs of other anatomic sites, suggest that the molecular context may be important when selecting therapies for women with endometrial NEC. Immune checkpoint inhibition may be a reasonable approach to treatment of microsatellite instability-NEC and we thus recommend that all endometrial NEC be tested for mismatch repair abnormalities, either molecularly or by mismatch repair protein immunohistochemistry.

PD-L1 Expression in Endocervical Adenocarcinoma

Programmed death-1 ligand (PD-L1) expression has been used as a predictive marker for response to immune checkpoint inhibitors and has been reported to have prognostic value. Its prevalence and significance in endocervical adenocarcinoma (ECA) remain underinvestigated. We evaluated PD-L1 expression and CD8+ tumor-infiltrating lymphocyte density in whole tissue sections of 89 ECAs. PD-L1 expression was observed in 68% of ECAs by combined positive score (CPS, cutoff 1) and 29% of ECAs by tumor proportion score (TPS, cutoff 1%). Using CPS, PD-L1 expression was seen in 11%, 78%, and 72% of pattern A, B, and C tumors, respectively, with significantly higher expression in tumors with destructive-type invasion (B and C) (P=0.001 [A vs. B], 0.0006 [A vs. C], 0.0002 [A vs. B+C]). Using TPS, no significant difference in PD-L1 expression was seen between tumors with different invasion patterns (0%, 22%, and 32% in tumors with pattern A, B, and C, respectively; P=0.27 [A vs. B], 0.053 [A vs. C], 0.11 [A vs. B+C]). PD-L1-positive ECAs demonstrated significantly higher CD8+ tumor-infiltrating lymphocyte density (CPS: P=0.028; TPS: P=0.013) and worse progression-free survival when compared with PD-L1-negative ECAs (CPS: hazard ratio [HR]=4.253 vs. 0.235, P=0.025; TPS: HR=4.98 vs. 0.2; P=0.004). When invasion patterns were separately assessed, pattern C tumors similarly showed worse progression-free survival in PD-L1-positive tumors (CPS: HR=6.15 vs. 0.16, P=0.045; TPS: HR=3.78 vs. 0.26, P=0.027). In conclusion, our data show frequent PD-L1 expression in ECA with destructive-type invasion, supporting the role of the PD-1/PD-L1 pathway as a therapeutic target for these tumors. Our data also support PD-L1 as a negative prognostic marker associated with a potentially unfavorable outcome.

Embryonal Rhabdomyosarcoma of the Uterine Cervix

Embryonal rhabdomyosarcoma of the uterine cervix (cERMS) is rare and frequently associated with DICER1 mutations. We report 94 tumors that arose in patients aged 7 to 59 (median=23) years and presented with vaginal bleeding (52), protruding vaginal mass (17), cervical polyp (8), or expelled tumor fragments per vagina (5). Nine had DICER1 syndrome, 8 of whom had other syndromic manifestations including ovarian Sertoli-Leydig cell tumor (7), multinodular goiter (3), pleuropulmonary blastoma (2), pineoblastoma (1), and osteosarcoma (1). Syndromic patients were younger than nonsyndromic patients (16 vs. 24 y). Tumor size ranged from 2 to 24 (median=4.5) cm. Ninety-two tumors were polypoid, most being grape-like (77 of 92). They were characterized by aggregates of primitive cells, almost always exhibiting a cambium layer, within a variably myxoedematous stroma and were hypocellular (63), moderately cellular (22), or hypercellular (9). Entrapped glands, typically scant, were present in 84 tumors. Primitive hyperchromatic ovoid to spindled cells with minimal cytoplasm predominated but differentiated rhabdomyoblasts with abundant eosinophilic cytoplasm (having cross-striations in 30) were seen in 83 tumors; they were often sparse but predominated in three. Nine tumors showed areas of intersecting fascicles and 4 zones with densely cellular (solid) growth. Cartilage was present in 38. Anaplasia was seen in 15 tumors, as was necrosis. Mitotic activity ranged from 1 to 58/10 high-power fields (median=8). The varied microscopic features resulted in a spectrum of differential diagnostic considerations, mainly typical and cellular forms of fibroepithelial polyps, Mullerian adenosarcoma, and other sarcomas. Follow-up was available for 79 patients ranging from 6 to 492 (median=90) months. Treatment information was available in 62 and included polypectomy in 6 patients (2 also received chemotherapy), limited resection in 26 (14 also received chemotherapy), hysterectomy in 29 (15 with adjuvant chemotherapy), and biopsies only in 1 (with chemotherapy). Staging was possible in 56 tumors; according to the “uterine sarcoma” system (tumor size and extent) they were: stage I (10/56; could not be further subclassified as size not available), IA (22/56), IB (18/56), IIA (2/56), IIB 3/56), IIIC (1/56). According to the “adenosarcoma” system (depth of invasion and extent) they were: stage IA (26/56), IB (14/56), IC (10/56), IIA (2/56), IIB (3/56), IIIC (1/56). Eight patients had local recurrence following incomplete excision (10%). Eleven of 79 patients had extrauterine recurrences (14%) and 9 died of disease (11%). Older age was associated with extrauterine recurrence (median 44 vs. 22; P=0.002) and decreased disease-specific survival (median 44 vs. 22; P=0.02). For patients with tumors initially confined to the cervix, the adenosarcoma staging system was superior to the uterine sarcoma staging system for predicting survival (P=0.02). Three patients with DICER1 syndrome who underwent fertility-preserving surgery developed a second primary cERMS 7, 7, and 12 years after their primary tumor. All 9 patients with DICER1 syndrome had tumors confined to the cervix and none died of disease. This study highlights the intriguing clinical aspects of cERMS including its long-known tendency to occur in the young but also more recently appreciated association with DICER1 syndrome. Establishing the diagnosis may still be difficult because of the hazard of sampling a neoplasm which in areas may appear remarkably bland and also because of its potential confusion with other neoplasms. This study indicates that this tumor has a good prognosis at this site and in selected cases a conservative surgical approach is a realistic consideration.

NTRK-Rearranged Uterine Sarcomas: Clinicopathologic Features of 15 Cases, Literature Review, and Risk Stratification

NTRK-rearranged uterine sarcomas are rare spindle cell neoplasms that typically arise in the uterine cervix of young women. Some tumors recur or metastasize, but features which predict behavior have not been identified to date. Distinguishing these tumors from morphologic mimics is significant because patients with advanced stage disease may be treated with TRK inhibitors. Herein, we present 15 cases of NTRK-rearranged uterine sarcomas, the largest series to date. Median patient age was 35 years (range: 16 to 61). The majority arose in the uterine cervix (n=14) and all but 2 were organ-confined at diagnosis. Tumors were composed of an infiltrative, fascicular proliferation of spindle cells and most showed mild-to-moderate cytologic atypia. All were pan-TRK positive by immunohistochemistry (13/13); S100 (11/13) and CD34 (6/10) were usually positive. RNA or DNA sequencing found NTRK1 (10/13) and NTRK3 (3/13) fusions with partners TPR, TPM3, EML4, TFG, SPECC1L, C16orf72, and IRF2BP2. Unusual morphology was seen in 2 tumors which were originally diagnosed as unclassifiable uterine sarcomas, 1 of which also harbored TP53 mutations. Follow up was available for 9 patients, of whom 3 died of disease. By incorporating outcome data of previously reported tumors, adverse prognostic features were identified, including a mitotic index ≥8 per 10 high-power fields, lymphovascular invasion, necrosis, and NTRK3 fusion. Patients with tumors which lacked any of these 4 features had an excellent prognosis. This study expands the morphologic spectrum of NTRK-rearranged uterine sarcomas and identifies features which can be used for risk stratification.

Clear Cell Carcinoma (CCC) of the Cervix Is a Human Papillomavirus (HPV)-independent Tumor Associated With Poor Outcome

Cervical clear cell carcinoma (CCC) is a rare human papillomavirus–independent adenocarcinoma. While recent studies have focused on gastric-type endocervical adenocarcinoma (GTA), little is known about CCC. A total of 58 (CCCs) were collected from 14 international institutions and retrospectively analyzed using univariable and multivariable methods and compared with 36 gastric-type adenocarcinomas and 173 human papillomavirus–associated (HPVA) endocervical adenocarcinoma (ECA) regarding overall survival (OS) and recurrence-free survival (RFS). Most cases were FIGO stage I (72.4%), with Silva C pattern of invasion (77.6%), and the majority were treated with radical surgery (84.5%) and adjuvant therapy (55.2%). Lymphovascular invasion was present in 31%, while lymph node metastasis was seen in 24.1%; 10.3% were associated with abdominopelvic metastases at the time of diagnosis; 32.8% had recurrences, and 19% died of disease. We did not find statistically significant differences in OS and RFS between CCC and GTA at 5 and 10 years (P=0.313 and 0.508, respectively), but there were significant differences in both OS and RFS between CCC and HPVA ECA (P=0.003 and 0.032, respectively). Also, OS and RFS in stage I clear cell and GTA were similar (P=0.632 and 0.692, respectively). Multivariate analysis showed that OS is influenced by the presence of recurrence (P=0.009), while RFS is influenced by the FIGO stage (P=0.025). Cervical CCC has poorer outcomes than HPVA ECA and similar outcomes to human papillomavirus–independent GTA. Oncologic treatment significantly influences RFS in univariate analysis but is not an independent prognostic factor in multivariate analysis suggesting that alternative therapies should be investigated.

Cervical Precancers Originate From Infected Proliferating Reserve Cells

Human papillomavirus (HPV)-induced invasive cervical squamous cell cancer (SCC) develop via high-grade squamous intraepithelial lesion (HSIL). In contrast to classic thick HSIL, thin HSIL (≤9 cell layers) are poorly documented. This study compares histology, HPV genotypes, and aberrations in 50 cancer genes of 45 thin HSIL to 45 thick HSIL, 20 pT1a SCC, and 40 ≥pT1b SCC. Thin HSIL arose from proliferating reserve cells within endocervical epithelium or immature metaplasia throughout the transformation zone after infection with high-risk HPV genotypes (36/45; 80%), and 20% non–high-risk HPV genotypes compared with 2.5% thick HSIL, pT1a SCC, and ≥pT1b SCC. Thin HSIL were multifocal proliferations with varying epithelial thickness between 1 and 2 to 9 cell layers, with occasional transitions to thick HSIL or concomitant lesions of thick HSIL. Overall, 40% thin HSIL were located distant to and most thick HSIL occurred near or at the squamocolumnar junction. Only 20% thick HSIL showed koilocytosis. All HSIL lacked somatic gene mutations, compared with 30% pT1a and 55%≥pT1b SCC. Overrepresented rare germline variants in the MET, JAK3, and FGFR3 genes occurred in all patient groups. In summary, thin and thick HSIL arose independently of somatic gene mutations. The maturation level of the squamous epithelium at the time of transforming infection determines if a thick HSIL develops directly from HPV-infected proliferating reserve cells via thin HSIL or in stratified glycogenated squamous epithelium via low-grade squamous intraepithelial lesion. These observations raise doubts about the biological relevance of separation into thin and thick HSIL. The oncogenic potential of HPV genotypes but also germline variants may influence the natural history.

HPV-negative Squamous Cell Carcinomas of the Cervix With Special Focus on Intraepithelial Precursor Lesions

Recently, the World Health Organization (WHO) recognized human papilloma virus (HPV)-independent invasive cervical squamous cell carcinoma (SCC) without recognizing the existence of precursor lesions. This is a detailed characterization of 3 preinvasive lesions and 6 invasive SCC negative for HPV-DNA (32 genotypes), HPV-mRNA (14 genotypes) and genomic HPV sequencing. We evaluated histologic features, expression of p16ink4a, p53, CK7, and CK17, aberrations in 50 cancer genes and chromosomal copy number variations. HPV-negative preinvasive lesions were extensive basaloid or highly differentiated keratinizing intraepithelial proliferations of 3 to 20 cell layers thickness, partly with prominent cervical gland involvement. Overall, 2/3 intraepithelial lesions and the in situ component of 1/6 SCC showed p16ink4a block staining, while 1/6 in situ component revealed heterogenous p16ink4a staining. All invasive components of keratinizing SCC were p16ink4a-negative. Preinvasive and invasive SCC showed inconsistent CK7 and CK17 staining. Nuclear p53 overexpression was restricted to the TP53 gene mutated SCC. The highly vascularized peritumoral stroma showed a dense inflammatory infiltrate including plasma cells and intratumoral and peritumoral eosinophilic granulocytes. Inconsistent somatic gene mutations (PIK3CA, STK11, TP53, SMARC2B, and GNAS) occurred predominantly in nonhotspot locations at low mutational frequency in 3/6 SCC. Consistent aberrations included the pathogenic (angiogenic) germline polymorphism Q472H in the KDR gene (7/9 patients), and chromosome 3q gains (4/9 patients). In conclusion, HPV-negative intraepithelial cervical precancerous lesions exist, either as highly differentiated keratinized intraepithelial proliferations reminiscent of differentiated vulvar intraepithelial neoplasia, or undifferentiated basaloid intraepithelial lesions with occasional p16ink4a block staining resembling high-grade squamous intraepithelial lesion. Gains of chromosome 3q, angiogenic germline variants the inflammatory infiltrate may contribute to progression of HPV-negative cervical carcinogenesis.

Tumoral Morphologic Features From Cervical Biopsies That Are Predictive of a Negligible Risk for Nodal Metastasis and Tumor Recurrence in Usual-type Cervical Adenocarcinomas

The metastatic or recurrent potential of localized human papillomavirus–associated endocervical adenocarcinoma (HPVA EAC) is difficult to predict, especially based upon biopsy alone. Recent analyses of small cohorts indicate that high tumor nuclear grade (TNG) and the presence of necrotic tumor debris (NTD) from HPVA EACs in cervical biopsy specimens are highly predictive of nodal metastasis (NM). In the present study, we aimed to investigate how reliably tumoral morphologic features from cervical biopsy specimens predict NM or tumor recurrence (TR) and patient outcomes in a large cohort of endocervical adenocarcinoma patients. A cohort comprised of 397 patients with HPVA EAC treated at 18 institutions was identified, and cervical biopsies were paired with their associated complete tumor resections for a total of 794 specimens. A variety of tumoral histologic features were examined for each paired specimen, including TNG (assessed on a 3-tiered scale of increasing abnormalities—TNG1, TNG2, TNG3) and NTD (defined by the presence of necrotic and apoptotic tumor cells within tumor glandular lumens admixed with granular and eosinophilic amorphous material and inflammatory cells), which were correlated with outcomes. The distribution of TNG in biopsies was as follows: 86 (21.7%) TNG1, 223 (56.2%) TNG2, and 88 (22.2%) TNG3. NTD was identified in 176 (44%) of the biopsy specimens. The sensitivity, specificity, positive predictive value, and negative predictive value of a TNG1 assignment in the biopsy being predictive of the same assignment in the full resection were 0.82 (95% confidence interval [CI]: 0.7-0.9), 0.895 (0.86-0.93), 0.593 (0.48-0.696), and 0.96 (0.94-0.98), respectively. Respective values for an NTD-negative status were 0.89 (95% CI: 0.83-0.92), 0.715 (0.64-0.77), 0.72 (0.65-0.77), and 0.89 (0.83-0.93), respectively. Compared with the other cases in each category, both TNG1 and an NTD-negative status were each significantly associated with lower rates of NM (odds ratio for TNG1=0.245, 95% CI: 0.070-0.857, P=0.0277; for NTD=0.199, 95% CI: 0.094-0.421, P<0.0001) and TR (odds ratio for TNG1=0.225, 95% CI: 0.051-0.987, P=0.0479; for NTD=0.367, 95% CI: 0.171-0.786, P=0.0099) independent of depth of stromal invasion, lymphovascular invasion, tumor size, FIGO stage, and Silva pattern. Overall, 73/379 (19%) cases were both TNG1 and NTD-negative on the biopsy, and none of these 73 cases showed NM (0%), but a single case (1.4%) showed TR. In contrast, among the 324 biopsies with TNG2/3 and/or presence of NTD, 62 (19.1%) had NM, and 41 (12.9%) had TR. In summary, 2 variables in combination (ie, TNG1 and NTD-negative) identified a subset of HPVA EAC patients—∼19%—with a 0% frequency of nodal metastases and only 1.4% frequency of recurrence. Biopsies highly but imperfectly predicted these features. Nonetheless, these findings may potentially be of clinical utility in the risk stratification of patients with HPVA EACs. This may allow some patients with a minimal risk of nodal metastases and TR to be identified at the biopsy phase, thereby facilitating more personalized, possibly less aggressive treatment.

Somatic Malignancies Arising in Ovarian Mature Cystic Teratomas

Somatic malignancy arising in ovarian mature cystic teratoma (MCT) is a relatively rare phenomenon with an estimated incidence ranging from 0.17% to 5.5%. Most previous studies have been limited by small sample sizes, hindering more precise estimates of incidence as well as providing limited prognostic information. We aimed to conduct a large-scale, multi-institutional study to better define incidence, discuss prognosis, and report occurrences of unusual malignancies arising in MCT. The pathology archives of the Massachusetts General Hospital and Brigham and Women’s Hospital were searched for all cases of MCT arising between 2006 and 2021. The pathology reports were reviewed for the presence of somatic malignancy arising within MCT. Cases harboring somatic malignancy were re-reviewed by a gynecologic pathologist, with documentation of a number of histomorphologic variables, including surface involvement, lymphovascular invasion, and tumor size. Sociodemographic variables, adjuvant chemotherapy, disease recurrence/progression, and survival were extrapolated from the medical record. Among 2416 cases of MCT, 40 cases of somatic malignancy were identified. Tumors included squamous cell carcinoma (SCC, n=21), papillary thyroid carcinoma (PTC, n=7), sebaceous carcinoma (n=2), neuroendocrine carcinoma (n=2), and other rarer types. The mean age of patients was 49 years (range: 17.7 to 69.7 y). Follow-up data was available for 20 patients (range: 3 to 196 mo, mean: 80.5 mo). Eleven were ovarian confined without surface involvement; 9 were AJCC stage pT1C or higher at the time of diagnosis. Of ovarian confined tumors without surface involvement, only 1 recurred (a follicular variant of papillary thyroid carcinoma) with bone metastases found 72 months after initial diagnosis. Four additional cases, all of which were stage 1C or higher at initial diagnosis, recurred after initial resection, including 2 cases with SCC, 1 melanoma case, and 1 adenocarcinoma ex-Goblet cell carcinoid case. Tumors that recurred tended to have a large malignant component (range: 4 to 23 cm, mean: 16.8 cm). When cases received in consultation were excluded, the overall incidence of incidental somatic malignancy arising in MCT was 0.54% (13 of 2389 cases). Somatic malignancy in MCT is rare, and outcomes largely depend on the stage at initial diagnosis, and possibly, the size of the malignant portion of the tumor. Poor outcomes were noted across multiple histologies. Patients diagnosed with early-stage disease (stage IA) generally had a favorable prognosis, whereas those with advanced-stage disease (stage IC or higher) faced higher risks of recurrence and mortality. Nevertheless, some low-stage patients experienced recurrence, highlighting the need for long-term follow-up for all patients. More aggressive management strategies should be tailored on a case-by-case basis. The focality of residual MCT, in some cases, underscores the need for a thorough sampling of ovarian somatic tumors without a known primary site. Careful pathologic evaluation, particularly of solid areas, is critical to detect malignancy in MCTs.

FGFR1 Mutations Are Rare Alternate Oncogenic Drivers in FOXL2-Wildtype Adult Granulosa Cell Tumors of the Ovary

Adult granulosa cell tumors (aGCTs) of the ovary are uniquely characterized by an almost ubiquitous somatic mutation in the FOXL2 gene (p.C134W). We report the first series of 7 aGCTs harboring pathogenic FGFR1 kinase domain mutations, providing a novel alternative oncogenic mechanism in these rare FOXL2 -wildtype tumors. Archival sex cord-stromal tumors that underwent targeted DNA sequencing (MSK-IMPACT, Oncopanel, and Foundation Medicine assays) were reviewed. Histopathologic and immunophenotypic features were reviewed by expert pathologists. Seven cases were identified with FGFR1 hotspot mutations (codons N546, N577, K656, and K687), 6 of which lacked the pathognomonic FOXL2 p.C134W variant. All tumors demonstrated the classic histology of aGCT (microfollicular growth, Call-Exner bodies, “coffee bean” nuclei) with 5/5 showing robust inhibin-α positivity by immunohistochemistry. No distinct morphologic or immunophenotypic differences were found compared with conventional FOXL2 -mutant aGCTs. Clinically, most patients presented at early stage (IA) and underwent surgical management. Four patients experienced recurrent disease involving peritoneal or omental sites, but overall clinical behavior was comparable to typical aGCTs. These findings establish FGFR1 alterations as an alternative oncogenic driver in a subset of FOXL2 -wildtype aGCTs. From a diagnostic standpoint, the absence of FOXL2 p.C134W mutation does not exclude the diagnosis of aGCT when the morphology and immunoprofile are characteristic.

Adult Granulosa Cell Tumors of the Ovary With Tubular Differentiation

Occasional ovarian sex cord-stromal tumors exhibit features suggestive of more than 1 subtype, including some with areas of both “female” (granulosa) and “male” (Sertoli and/or Leydig) cell types. These tumors, historically often referred to as “gynandroblastomas,” are frequently difficult to classify due to considerable clinical and morphologic heterogeneity. Herein, we describe a particular pattern of differentiation in which tubules occurred within tumors whose overall clinicopathologic features indicate that they are best characterized as adult granulosa cell tumors (AGCT). Eighty tumors were identified. Patient ages ranged from 15 to 87 (median: 52) years, and 28 had endocrine manifestations (25 estrogenic; 3 androgenic). Follow-up was available in 13 patients and ranged from 10 to 266 (median: 60) months, disclosing recurrence in 2. Microscopically, all tumors not only contained areas of typical granulosa cell morphology (diffuse, trabecular, corded, and others), which often dominated, but also contained variable amounts of hollow and/or solid tubules resembling those seen in Sertoli cell tumors. Next-generation sequencing was successful in 11 tumors. Two of these harbored FOXL2 p.C134W variants, and 2 others had FOXL2 copy number gains; none had DICER1 mutations. On the basis of the average age of the patients, frequency of estrogenic manifestations, abundance of standard AGCT morphology, and occasional late recurrences, we suggest that these tumors form a distinct group and propose the term “AGCTs with tubular differentiation” to denote them.

“Early” Clear Cell Proliferations (Clear Cell Carcinoma in Situ) in Ovarian Endometriotic Cysts

Clear cell carcinoma (CCC) is an uncommon malignancy accounting for ∼12% of ovarian carcinomas. Most cases arise from endometriosis, frequently an endometriotic cyst. We report a series of 6 cases where clear cell proliferations, morphologically, and immunophenotypically consistent with CCC, involve the epithelial lining of an endometriotic cyst without invasion into the surrounding stroma. The patients were aged 29 to 63 years (mean 45). In all cases, epithelial proliferations composed of cells with atypical nuclei, sometimes with a hobnail morphology, and clear or eosinophilic cytoplasm involved the epithelial lining of an ovarian endometriotic cyst. In areas, the proliferations comprised a monolayer, but in all cases, there was also significant epithelial stratification and multilayering, sometimes with a pseudopapillary architecture. There was no invasion of the atypical cells into the surrounding ovarian stroma. The proliferations were positive for Napsin A (6 of 6; 4 diffuse, 2 focal), racemase (5 of 5; 3 diffuse, 2 focal), hepatocyte nuclear factor 1-beta (5 of 5; all diffuse), oestrogen receptor (5 of 6; 2 diffuse, 3 focal), and PAX8 (3 of 3; all diffuse). p53 was wild-type in all 6 cases and WT1 and progesterone receptor were negative in the 4 and 6 cases tested, respectively. Mismatch repair immunohistochemistry was retained in the 3 cases tested. Next-generation sequencing was performed in 2 cases. In 1 case, a sole pathogenic MSH6 variant (p.Ser65fs) was identified. Follow-up (2 to 24 months) was available in 5 cases and there was no tumour recurrence. In reporting these “early” clear cell proliferations in endometriotic cysts, we provide recommendations for the reporting pathologist regarding the most appropriate terminology, which is important in patient management. We suggest that these proliferations be termed “CCC in situ” and that identification of such a lesion should prompt extensive sampling in order to exclude an invasive CCC component within the stroma outside the endometriotic cyst lining. We also stress the importance of close dialogue between the pathologist and the clinician and between the clinician and the patient in order to avoid overtreatment in such cases.

The Malignant Potential of Ovarian Steroid Cell Tumors Revisited

Steroid cell tumors (SCTs) of the ovary are rare and understudied, and as such, uncertainties remain about their malignant potential, as well as clinicopathologic predictors of patient outcome. Based on a multi-institutional cohort of cases, we present findings from the largest study of SCT reported to date. Clinicopathologic data were documented on 115 cases of SCT that were assembled from 17 institutions. The median patient age was 55 years (range: 9 to 84). When measured, preoperative androgen levels were elevated in 84.2% (48/57) of patients. A total of 111 (96.5%) cases were classified as stage I (103 stage IA; 2 stage IB; 6 stage IC). The stage distribution for the remaining 4 patients was as follows: stage II (n = 1), III (n = 3; 1 IIIA, 1 IIIB, 1 IIIC). The median tumor size was 3 cm (range: 0.2 to 22). Cytologic atypia, microscopic tumor necrosis, microscopic tumor hemorrhage, and a mitotic index of >1 mitotic figure/10 high-power fields were present in 52% (60/115), 9.6% (11/115), 37% (43/115), and 19% (22/115) of cases, respectively. Of 115 patients, 7 (6.1%) recurred postexcision, 4 (3.5%) ultimately died of disease, and 10 (8.7%) either recurred, died of disease, or were advanced stage at presentation. The median duration to recurrence postresection was 33 months (range: 23 to 180). Four of the 7 recurrences were stage IA at baseline. Tumor size >4 cm, International Federation of Gynecology and Obstetrics (FIGO) stage ≥IB, tumor necrosis, and tumor hemorrhage were each significantly associated with reduced recurrence-free survival in log-rank tests and univariable Cox models, with age older than 65 years being of marginal significance (hazard ratio [HR]: 5.4, 95% CI: 1.0-30.0, P = 0.05). Multivariable analyses suggested that FIGO stage ≥IB (HR: 27.5, 95% CI: 2.6-290.5), and age older than >65 years (HR: 21.8, 95% CI: 1.6-303.9) were the only parameters that were independently associated with recurrence. Cross-section analyses showed that tumor necrosis, tumor hemorrhage, and larger tumor size were significantly associated with a FIGO stage ≥IB status, which bolstered the conclusion that they are not independent predictors of recurrence. In summary, <10% of SCTs are clinically malignant, a substantially lower frequency than has previously been reported in the literature. Clinicopathologic predictors of patient outcomes that are prospectively applicable in practice could not be definitively established. Recurrences may occur many years (up to 15 y in this study) after primary resection, even in stage IA cases.

Ovarian Carcinomas

According to histopathology and molecular genetics, there are 5 major subtypes of ovarian carcinomas: high-grade serous (70%), endometrioid (10%), clear cell (10%), mucinous (3% to 4%), and low-grade serous (<5%) carcinomas. These tumors, which constitute over 95% of cases, represent distinct diseases with different prognoses and therapy. This review outlines contemporary advances in molecular pathology, which have expanded our knowledge of the biology of epithelial ovarian cancer and are also important to patient management. We also comment on some controversial points of the FIGO staging classification that we proposed in 2014.

Uterine Tumors Resembling Ovarian Sex Cord Tumors

Uterine tumors resembling ovarian sex cord tumors (UTROSCTs), first characterized by Drs Clement and Scully in 1976, are rare neoplasms showing clinical, morphologic, and immunohistochemical overlap with a number of other uterine tumors, most being mesenchymal. Criteria for aggressive behavior are not clearly established. We report 75 tumors from patients ranging from 21 to 84 (mean=52.4) years. Seventy-one patients were treated by hysterectomy and 4 by conservative total excision. Thirty-eight tumors were intramyometrial, 34 submucosal, and 3 cervical; they ranged from 0.6 to 20 (mean=4.9) cm and were typically tan-yellow. Sixty-eight neoplasms were well-circumscribed and 7 had infiltrative borders (4 only minimally). In 56 tumors, a smooth muscle component was intimately admixed with the neoplastic cells (“pseudoinfiltration”; extensive in 29). Architectural patterns included cords (n=53), diffuse (n=51), hollow tubules (n=48), nests (n=38), trabeculae (n=37), retiform (n=23), solid tubules (n=21), pseudoangiomatoid (n=11), pseudopapillary (n=4), and whorled (n=2); typically, more than 1 pattern was seen. Tumor cells were epithelioid (n=62), epithelioid and spindled (n=12), or spindled (n=1) and/or rhabdoid (n=20; extensive in 2). Cytologic atypia was absent to mild in 57, moderate in 16, and moderate to severe in 2 tumors. Fifty-seven UTROSCTs had ≤2mitoses/10 high power fields (HPF), 12 had 3 to 5/10 HPF, and 6 >5/10 HPF. Necrosis was present in 3 and lymphovascular invasion in 1. Tumor cells showed a polyphenotypic immunohistochemical profile (with positivity for sex cord, smooth muscle, and epithelial markers), most commonly inhibin (17/33+) and calretinin (22/31+) positive. Five of 58 patients with follow-up (22 to 192; mean=73.2 mo) had recurrences/metastases from 30 to 144 months, and 2 died of disease. Malignant tumors showed >3 of the following 5 features compared with benign tumors: size >5 cm, at least moderate cytologic atypia, ≥3 mitoses/10 HPF, infiltrative borders, and necrosis. One of the 5 malignant tumors showed an extensive rhabdoid morphology. UTROSCTs are uncommon, show a wide morphologic spectrum, often pose problems in differential diagnosis, and typically have a benign outcome. Rare tumors are associated with late recurrences and a combination of more than 3 of the 5 features listed above predicted aggressive behavior in this series.

Loss of Major Histocompatibility Complex Class I, CD8+ Tumor-infiltrating Lymphocytes, and PD-L1 Expression in Ovarian Clear Cell Carcinoma

Ovarian clear cell carcinoma (OCCC), a chemoresistant ovarian cancer, shows a modest response to anti–programmed death-1/programmed death ligand-1 (PD-1/PD-L1) therapies. The effects of anti-PD-1/PD-L1 therapies rely on cytotoxic T-cell response, which is triggered by antigen presentation mediated by major histocompatibility complex (MHC) class I. The loss of MHC class I with simultaneous PD-L1 expression has been noted in several cancer types; however, these findings and their prognostic value have rarely been evaluated in OCCC. We collected data from 76 patients with OCCC for clinicopathologic analysis. Loss of MHC class I expression was seen in 44.7% of the cases including 39.3% to 47.4% of the PD-L1+ cases and was associated with fewer CD8+ tumor-infiltrating lymphocytes (TILs). PD-L1 positivity was associated with a higher number of CD8+ TILs. Cox proportional hazard models showed that high (≥50/mm2) CD8+ TILs was associated with shorter disease-specific survival (hazard ratio [HR]=3.447, 95% confidence interval [CI]: 1.222-9.720, P=0.019) and overall survival (HR=3.053, 95% CI: 1.105-8.43, P=0.031). PD-L1 positivity using Combined Positive Score was associated with shorter progression-free survival (HR=3.246, 95% CI: 1.435-7.339, P=0.005), disease-specific survival (HR=4.124, 95% CI: 1.403-12.116, P=0.010), and overall survival (HR=4.489, 95% CI: 1.553-12.972, P=0.006). Loss of MHC class I may contribute to immune evasion and resistance to anti-PD-1/PD-L1 therapies in OCCC, and CD8+ TILs and PD-L1 positivity using Combined Positive Score may have a negative prognostic value.

Ovarian Signet-ring Stromal Tumor

Signet-ring stromal tumor (SRST) is a rare ovarian stromal neoplasm characterized by a population of bland signet-ring cells, devoid of mucin or lipid, in a generally cellular fibromatous stroma. Previous reports have described heterogenous immunohistochemical and molecular genetic findings, including occasional nuclear β-catenin expression and/or CTNNB1 mutations. We report 10 ovarian stromal neoplasms originally diagnosed as SRST. All but 1 tumor underwent detailed immunohistochemical analysis (including β-catenin) and 5 of 10 had CTNNB1 mutation analysis performed. All tumors contained a population of morphologically bland signet-ring cells that ranged from 15% to 95% of the neoplasm, characterized by a single large empty intracytoplasmic vacuole, mostly with nuclear indentation. Six of the 10 tumors contained cellular fibroma-like areas, comprising from 10% to 85% of the neoplasm. Three of the 10 tumors were reclassified as microcystic stromal tumor with signet-ring cells on the basis of the microcyst formation and hyalinized stroma, beta-catenin and cyclin D1 nuclear expression and/or CTNNB1 mutation, CD10 staining and largely absent expression of inhibin and calretinin. In the remaining 7 tumors, the diagnosis of SRST remained, constituting the largest series of SRST reported in the literature to date. The results of our study suggest that a subset of tumors diagnosed as ovarian SRST, especially those which show β-catenin nuclear positivity and/or CTNNB1 mutation, likely represent microcystic stromal tumor with variant morphology. We also suggest that at least a subset of SRSTs without evidence of Wnt/β-catenin pathway abnormalities may be related to ovarian fibromas. We discuss the differential diagnosis of ovarian neoplasms containing signet-ring cells.

Mixed Ovarian Neoplasms With Gastrointestinal-type Mucinous and Mullerian Epithelial Components

Primary mucinous ovarian neoplasms, gastrointestinal-type (GI-type), are composed of mucin-producing tumor cells resembling intestinal goblet cells or gastric foveolar epithelium. In contrast to seromucinous tumors, which exhibit endocervical-type mucinous differentiation and are thought to be derived from endometriosis, the cell/tissue-of-origin of most GI-type mucinous ovarian tumors is unknown. We identified 8 GI-type mucinous ovarian tumors (cystadenomas, n=4; borderline tumor/carcinoma, n=4) with spatially distinct areas that showed morphologic features of Mullerian-type epithelial differentiation (ciliated cells or endometrioid-type glands). Immunohistochemistry for cell lineage markers and Alcian blue (pH 2.5)/Periodic Acid-Schiff staining were performed. Morphologically distinct components were isolated by microdissection, from which extracted DNA was analyzed by targeted next-generation sequencing. In all cases, immunohistochemistry demonstrated mucin-producing cells to be positive for at least one GI marker (CK20 or CDX2), while areas with morphologic features of Mullerian differentiation were positive for PAX8, ER and/or PR, and lacked expression of CK20 and CDX2; CK7 was strongly and diffusely positive in all tumor cells. Tumor cells with a gastric-type phenotype produced neutral mucin, while acidic mucin was present within intestinal-type goblet cells. Targeted sequencing revealed ARID1A mutations in all mixed borderline tumors/carcinomas (n=4); other recurrent genetic alterations included KRAS (n=2) and TP53 mutations (n=2). Shared mutations were present in paired Mullerian and GI-type mucinous tumor components in 4 mixed borderline tumors/carcinomas, with more shared mutations between components than private mutations specific to each component. All mixed borderline tumors/carcinomas were associated with endometriosis (n=3) or Mullerian inclusion cysts (n=1); mutation or loss of ARID1A expression was seen in these putative precursor lesions in 2 cases. Hence, ovarian neoplasms composed of clonally related GI-type mucinous and Mullerian-type epithelial components harbor ARID1A mutations and are frequently associated with endometriosis. The existence of a Mullerian stem/progenitor cell with the capacity to differentiate toward cell lineages within the GI-tract may be involved in the pathogenesis of at least a subset of GI-type mucinous ovarian neoplasms.

Reply to Letter by Cyrta et al, Entitled “Additional Considerations on Aberrant BRG1 (SMARCA4) Expression in Small Cell Carcinoma of the Ovary, Hypercalcemic Type (SCCOHT)”

Uterine Tumor Resembling Ovarian Sex Cord Tumors: 23 Cases Indicating Molecular Heterogeneity With Variable Biological Behavior

Uterine tumor resembling ovarian sex cord tumor (UTROSCT) is a rare mesenchymal neoplasm that mainly harbors NCOA1-3 rearrangements with partner genes ESR1 or GREB1. Here, we explored 23 UTROSCTs by targeted RNA sequencing. The association between molecular diversity and clinicopathologic features was investigated. The mean age of our cohort was 43 years (23–65 y). Only 15 patients (65%) were originally diagnosed with UTROSCTs. Mitotic figures ranged from 1 to 7/10 high power fields, of primary tumors and increased from 1 to 9/10 high power fields in recurrent tumors. Five types of gene fusions were identified in these patients, including GREB1::NCOA2 (n=7), GREB1::NCOA1 (n=5), ESR1::NCOA2 (n=3), ESR1::NCOA3 (n=7), and GTF2A1::NCOA2 (n=1). To our knowledge, our group included the largest cohort of tumors with GREB1::NCOA2 fusions. Recurrences were most common in patients with GREB1::NCOA2 fusion (57%), followed by 40% (GREB1::NCOA1), 33% (ESR1::NCOA2), and 14% (ESR1::NCOA3). The recurrent patient who harbored an ESR1::NCOA2 fusion was characterized by extensive rhabdoid features. Both of the recurrent patients who harbored GREB1::NCOA1 and ESR1::NCOA3 had the largest tumor sizes in their own gene alteration groups, and another recurrent GREB1::NCOA1 patient had extrauterine involvement. The GREB1-rearranged patients were of older age, larger tumor size, and higher stage than non-GREB1-rearranged patients (P=0.004, 0.028, and 0.016, respectively). In addition, the GREB1-rearranged tumors presented more commonly as intramural masses rather than non-GREB1-rearranged tumors presenting as polypoid/submucosal masses (P=0.021). Microscopically, nested and whorled patterns were frequently seen in GREB1-rearranged patients (P=0.006). Of note, estrogen receptor expression was weaker than progesterone receptor in all 12 GREB1-rearranged tumors, whereas the similar staining intensity of estrogen receptor and progesterone receptor was observed in all 11 non-GREB1-rearranged tumors (P<0.0001). This study demonstrated that UTROSCTs were present at a younger age in the Chinese population. The genetic heterogeneity of UTROSCTs was correlated with variable recurrence rate. Tumors with GREB1::NCOA2 fusions are more likely to recur compared with those with other genetic alterations.

CK17 Immunohistochemistry Is a Useful Adjunct in the Diagnosis of HPV-independent, TP53-wild-type Verruciform/Acanthotic Vulvar Intraepithelial Neoplasia (vaVIN)

Verruciform/acanthotic vulvar intraepithelial neoplasia (vaVIN) is a rare, recently defined HPV-independent, TP53-wild type lesion of the vulva that predisposes to vulvar squamous cell carcinoma (VSCC). VaVIN encompasses a variety of histomorphologic subtypes, including verruciform lichen simplex chronicus (vLSC), differentiated exophytic vulvar intraepithelial lesion (DEVIL), and vulvar acanthosis with altered differentiation (VAAD). Given the rarity of the lesion, subtle histopathologic features, and overlap with other preneoplastic entities and benign dermatoses, vaVIN is a diagnostic challenge. Therefore, immunohistochemistry (IHC) may be a helpful diagnostic adjunct in differentiating vaVIN from mimickers. Cytokeratin 17 (CK17) immunohistochemistry has been previously described as a useful diagnostic tool in diagnosing differentiated vulvar intraepithelial neoplasia (dVIN) and VSCC and has only recently been applied to vaVIN. In this study, we identified a total of ten cases of vaVIN, including four classified as vLSC, five classified as DEVIL, and one classified as VAAD. CK17 was expressed by all vaVIN lesions, with superficial to suprabasal expression in the vLSC subtype and uniform suprabasal expression in the DEVIL and VAAD subtypes. The pattern of CK17 expression may be helpful in differentiating vaVIN subtypes, notably demonstrating only superficial expression in some cases of the least aggressive phenotype, vLSC. Suprabasal expression corresponds to the more aggressive phenotypes of DEVIL and VAAD. However, additional confirmatory studies in a larger cohort are needed to validate these findings.

D2-40 and CK17 Immunohistochemistry as a Diagnostic Adjunct for HPV-Independent Squamous Lesions in the Vulva and Their Role in Defining Atypical Lichen Sclerosus

Vulvar lichen sclerosus (LS) is a common, chronic inflammatory disorder with a subset of cases progressing to differentiated vulvar intraepithelial neoplasia (dVIN) and/or squamous cell carcinoma (SCC). Histopathologic diagnosis of LS and dVIN can be challenging, and it is difficult to predict the subset of LS cases that progress. Immunohistochemistry (IHC) may be a useful diagnostic aid in this setting. CK17 has been shown to be overexpressed in invasive SCC and dVIN, and less commonly in LS. Similar to CK17, D2-40 has been correlated with cutaneous SCC prognosis but has not been evaluated in vulvar lesions. We identified a total of 13 patients with HPV-independent vulvar SCC that had precursor LS or dVIN. CK17 and D2-40 IHC stain intensity and pattern was scored in foci of LS, dVIN, and SCC. An increase in basal layer D2-40 expression was observed with progression from LS to dVIN with strong and diffuse staining in SCC. CK17 maintained similar stain intensity among squamous lesions, but displayed different patterns of staining, with superficial staining in LS, suprabasal staining in dVIN, and diffuse staining in SCC. A subset of LS cases displayed an intermediate (suprabasal) CK17 IHC profile, wild-type p53 expression, and cytomorphologic and architectural features intermediate between LS and dVIN; we defined such cases as “atypical LS.” We found that a panel of D2-40/CK17 can serve as a diagnostic adjunct to differentiate LS, dVIN, and invasive SCC. Additional studies with larger patient cohorts are needed to validate these findings and determine their prognostic significance.

HPV-independent Precursors Mimicking High-grade Squamous Intraepithelial Lesions (HSIL) of the Vulva

Two etiopathogenic types of vulvar squamous cell carcinoma (VSCC) have been described: human papillomavirus (HPV)-associated and HPV-independent. Precursor lesions, frequently identified in the adjacent skin, are also distinct in the 2 types of VSCC: high-grade squamous intraepithelial lesions (HSILs) in HPV-associated VSCC and differentiated vulvar intraepithelial neoplasia (dVIN) or vulvar acanthosis with altered differentiation in HPV-independent VSCC. Although HPV-independent precursors mimicking HSIL have been described in the vulva, their frequency and morphologic spectrum have not been completely characterized. We explored, in a large series of HPV-independent VSSC, the frequency and the histologic features of precursors mimicking HSIL. We included 779 DNA HPV-negative/p16-negative VSCC with at least 1 cm of adjacent skin. We evaluated the histologic and immunohistochemical (p16 and p53) characteristics of the intraepithelial lesions, focusing on precursors mimicking HPV-associated vulvar HSIL. A total of 254 tumors (33%) had adjacent premalignant lesions. Of them, 186 (73%) had dVIN, 22 (9%) had vulvar acanthosis with altered differentiation, and 46 (18%) had lesions that mimicked HSIL. The mean age of the patients with these HSIL-like lesions was 72±15 years. Twenty-six of these HSIL-like lesions had basaloid morphology, 13 warty, and 7 mixed basaloid/warty features. All the HSIL-like precursors were DNA HPV-negative/p16-negative; 74% of them showed p53 abnormal staining and 35% of them had areas of conventional dVIN. In conclusion, about one fifth of the HPV-independent precursors mimic HSIL, showing either basaloid or warty features. Older age and the presence of areas of typical HPV-independent intraepithelial lesions, together with p16 negativity, should raise suspicion of an HPV-independent etiology.

Extensive Pathologic Invasion and Prognostic Implication of Gastric-Type Cervical Adenocarcinoma

Gastric-type adenocarcinoma (GAS) is the most common subtype of human papillomavirus (HPV)-independent cervical adenocarcinomas and is associated with a poor prognosis. We used a gross morphologic classification system and imaging analysis to compare the clinicopathological features of GAS and HPV-associated adenocarcinoma (HPVA) and identify factors contributing to the poor prognosis of GAS. This retrospective 2-center study analyzed 33 patients with GAS and 70 with HPVA (stages IB-IVB) who underwent surgery between 1997 and 2023. GAS had a higher rate of positive surgical margins (21.2% vs. 0%, respectively, P<0.001) and unclear tumor boundaries on gross morphologic findings (47.8% vs. 8.8%, respectively, P<0.001). Discrepancies between clinical and pathologic T classifications were more common in GAS, leading to frequent upstaging (51.5% vs. 28.6%, respectively, P=0.029). Imaging analysis revealed that GAS was associated with a smaller median tumor cell area (19.8% vs. 55.7%, respectively, P<0.001), which was significantly correlated with unclear tumor boundaries. Perineural invasion (PNI) was significantly more frequent in GAS (69.7% vs. 10.0%, respectively, P<0.001). A Kaplan-Meier analysis showed that patients with PNI had significantly poorer overall survival (P<0.001). A Cox multivariate analysis identified an advanced pathologic stage, positive peritoneal cytology, and positive surgical margins as independent risk factors. The present results indicate that GAS has a unique “stealth” invasion pattern, possibly caused by low tumor density, leading to undetectable tumor boundaries and positive surgical margins. This suggests a greater risk of incomplete resection than HPVA, leading to a poorer prognosis.

Morphologic and Molecular Heterogeneity of Cervical Neuroendocrine Neoplasia

Neuroendocrine neoplasms (NENs) of the cervix are rare aggressive tumors associated with poor prognosis and only limited treatment options. Although there is some literature on molecular underpinnings of cervical small cell neuroendocrine carcinomas (SCNECs), detailed morphologic and associated molecular characteristics of cervical NENs remains to be elucidated. Herein, 14 NENs (SCNEC: 6, large cell neuroendocrine carcinoma [LCNEC]: 6, neuroendocrine tumor [NET]: 2), including 5 admixed with human papillomavirus (HPV)-associated adenocarcinoma (carcinoma admixed with neuroendocrine carcinoma) were analyzed. All except 3 SCNECs were HPV16/18 positive. TP53 (3) and/or RB1 (4) alterations (3 concurrent) were only seen in SCNECs (4/6) and were enriched in the HPV16/18-negative tumors. The other most common molecular changes in neuroendocrine carcinomas (NECs) overlapping with those reported in the literature for cervical carcinomas involved PI3K/MAPK pathway (4) and MYC (4) and were seen in both SCNECs and LCNECs. In contrast, the 2 NETs lacked any significant alterations. Two LCNECs admixed with adenocarcinoma had enough material to sequence separately each component. In both pathogenic alterations were shared between the 2 components, including ERBB2 amplification in one and an MSH6 mutation with MYC amplification in the other. Overall, these findings suggest that cervical HPV-associated NETs are genomically silent and high-grade NECs (regardless of small or large cell morphology) share molecular pathways with common cervical carcinomas as it has been reported in the endometrium and are different from NECs at other sites. Molecular analysis of these highly malignant neoplasms might inform the clinical management for potential therapeutic targets.

Claudin-18 as a Promising Surrogate Marker for Endocervical Gastric-type Carcinoma

HIK1083 and trefoil factor 2 (TFF2) are known to be expressed in gastric-type carcinoma (GAS), but they do not reliably mark all GASs, and focal expression can be missed in biopsy specimens. We aimed to investigate whether claudin-18 and alpha-methylacyl-CoA racemase (AMACR) could be surrogate markers to separate GAS from other types of endocervical adenocarcinoma (ECA) and to compare their usefulness with that of HIK1083 and TFF2. Claudin-18 and AMACR immunohistochemistry was performed, and the results were compared with that of TFF2 and HIK1083, using whole sections of 75 ECAs (22 GASs and 53 non-GASs) and 179 ECAs with tissue microarrays (TMAs). TMAs were built to simulate the assessment of immunohistochemical stains in small biopsies. Any membranous (claudin-18) or cytoplasmic/membranous (AMACR, TFF2, HIK1083) staining of >5% of tumor cells was considered positive. Of 75 ECAs with whole sections, claudin-18 was significantly more frequently expressed in GASs (21/22) compared with non-GASs (8/53) (P<0.01). In ECAs with TMAs, claudin-18 expression was significantly frequent in GASs (15/23, 65.2%) than in non-GASs (3/152, 2.0%; all usual-type) (P<0.01). All claudin-18-positive GASs showed intense staining except 1 case. Claudin-18 shared the same degree of sensitivity and specificity with HIK1083 and TFF2. Three clear cell carcinomas were positive for claudin-18, but none showed intense staining. AMACR was expressed in a subset of ECAs and showed no impact in distinguishing between GAS and other ECAs. Our results suggest that claudin-18 is a promising surrogate marker to separate GAS from other types of ECA, including clear cell carcinoma.

Adnexal Endometrioid Carcinomas With Sex Cord-Like Morphology are Frequently PAX8-Negative, SOX17-Positive, and Enriched for CTNNB1 Alterations

Sex cord-like morphology is now a well-known feature of occasional examples of endometrioid carcinoma of the ovary or fallopian tube. Recently, we have observed that these tumors are frequently negative for PAX8, prompting us to review their morphologic, immunohistochemical, and genomic spectrum. Twenty tumors (17 ovarian, 3 fallopian tube) with available tissue were identified in patients ranging from 32 to 78 (median 60) years. Sex cord-like patterns included cords/trabeculae (n=17), small tubular glands (n=16), and “granulosa-like” nests (n=12). In addition, 1 had ependymoma-like features with perivascular pseudorosettes and 3 had focal spindled cells. Conventional endometrioid glands were often sparse. All had conspicuous fibromatous stroma and 11 tumors had background endometrioid adenofibromas. Six tumors had associated endometriosis. PAX8 was positive in only 2/20 (diffuse in both), while SOX17 was positive in all (focal in 1, diffuse in 19). Beta-catenin showed aberrant nuclear staining in 17/20. Of the 10 sequenced tumors, 9 showed activating pathogenic variants in CTNNB1; each of these also showed nuclear beta-catenin staining. All lacked alterations in mismatch repair genes, TP53 , and POLE . In summary, adnexal endometrioid carcinomas with sex cord-like features are frequently PAX8-negative, which may result in diagnostic difficulty. However, SOX17 is typically positive and thus useful to establish the diagnosis. Most of these tumors are classified in the “no specific molecular profile” subgroup and have high rates of nuclear beta-catenin/ CTNNB1 alterations. Awareness of these morphologic and immunohistochemical associations may help avoid misclassification as sex cord-stromal or other neoplasms.

A Deeper Dive into POLE-Mutated Endometrial Carcinomas

POLE -mutated endometrial carcinomas ( POLE mut EC) have the most favorable prognosis among all TCGA molecular subgroups. Though the consequent “ultramutated” phenotype is recognized as a trademark feature, hypermutated tumors (10-100 mutations/megabase), as well as those that are histologically low-grade, have been described. Herein, we investigate 19 POLE mut ECs from a single institution to determine whether morphologic and genomic differences exist between tumors with high tumor mutational burden (TMB-H: 10-100 mutations/megabase) and ultra-high TMB (TMB-UH: >100 mutations/megabase). All tumors were FIGO stage I, of endometrioid histotype, and no patients recurred (median follow-up of 90 mo). Six previously described POLE exonuclease domain mutations were detected, with the 2 most common being P286R (n=7) and V411L (n=6). Seven ECs were TMB-H (median 76 mutations/megabase), and 12 TMB-UH (median 187 mutations/megabase). TMB-UH tumors were more frequently high-grade, with intratumoral heterogeneity, serous-like nuclei, and bizarre nuclei. Using an integrated approach, multiple classifiers were observed in both cohorts (53% of all tumors); however, those associated with MMRd were exclusive to TMB-UH ECs. All TMB-H ECs had a dominant (>50%) POLE mutational signature, in contrast to only 5 TMB-UH tumors. The remaining TMB-UH ECs demonstrated mixed signatures associated with mismatch repair deficiency (MMRd, n=4) or nonspecific signatures (n=3). All POLE mut tumors were enriched in single-nucleotide variants, while insertions-deletions were rare (maximum of 1.7%). In both groups, all harbored PTEN mutations, with other commonly recurring mutations including PIK3CA, ATRX, BRCA2, FBXW7 , and NF1 . ARID1A mutations were not identified in any TMB-H ECs. Although our cohort is small, the morphology of POLE mut ECs appears to be influenced by TMB, a phenomenon not yet described in the evolving landscape of these tumors. Taken in combination with differences in underlying genomic signatures, these findings provide an interesting springboard for better understanding POLE mut EC pathobiology.

Anaplastic Juvenile Granulosa Cell Tumor: A Report of 10 Cases of an Unemphasized Variant With Adverse Prognostic Features Characterized by TP53 Inactivation With MYC Family Amplifications

Ten anaplastic juvenile granulosa cell tumors (JGCT) with architectural and cytologic features that differ from those seen in conventional JGCTs were identified from patients who ranged from 7 to 44 (median 13) years. The tumors measured from 8.3 to 28 (median 21) cm. FIGO stage was IA (n=3), IC3 (n=2), II (n=1), IIIA (n=3), or unknown (n=1). All tumors had conventional areas with solid/nodular growth usually punctuated by follicles. However, all demonstrated areas (median 50%, range: 10% to 90%) with effacement of this architecture, characterized by diffuse growth, marked cytologic atypia, and brisk mitoses (up to 40/10 HPFs). In contrast, the conventional component exhibited significantly less atypia and mitoses. Next-generation sequencing was performed in 7 tumors and all harbored TP53 mutations; the remaining 3 showed aberrant p53 expression by immunohistochemistry. MYC family ( MYC and MYCN ) amplifications were identified in 4 tumors, while other alterations included AKT1 in-frame duplications (n=4) and DICER1 mutations (n=2). Follow-up was available for 9 patients (median 22 mo); 4 died of disease (all stage II/III with MYC/MYCN amplifications), one was alive with disease (stage IA), and 4 were alive and well (stages IA/IC). Anaplastic JGCTs have a distinct morphologic appearance and consistently demonstrate TP53 inactivation, with MYC family amplification evident in advanced-stage tumors. Although it cannot be determined whether MYC family amplifications are an independent predictor of behavior, they are important to recognize as such patients may benefit from MYC inhibitors. Tumors with the features described herein should be distinguished from conventional JGCTs because of the prognostic implications. In addition, the architectural deviations from that usually encountered and pleomorphism further add to diagnostic challenges in evaluating JGCTs.

Performance Assessment of a Deep Learning–based Algorithm for Ovarian Cancer Histotyping in an Independent Data Set

Artificial intelligence diagnostic tools show promise for improving histotype classification in epithelial ovarian cancer but face challenges due to slide variability across institutions. To address this domain shift, the adversarial Fourier-based domain adaptation (AIDA) model was developed. This retrospective study evaluates AIDA’s performance in classifying the 5 major ovarian cancer subtypes using an independent cohort. Surgically treated patients diagnosed with clear cell (CCC), endometrioid (EC), high-grade serous (HGSC), low-grade serous (LGSC), or mucinous (MC) ovarian cancer at Amsterdam University Medical Center (1985-2022) were included in the study. The deep learning method AIDA, trained on data from Vancouver General Hospital, was applied to all cases. Final histotype predictions were made through majority voting across 15 independently trained models. For misclassified cases, up to 3 additional slides were scanned, and the AIDA model was retrained. Classification was then assessed using single-slide and majority voting approaches. The AIDA algorithm achieved an overall balanced accuracy of 79.7% across all histotypes. Accuracy was highest for CCC (90.9%) and LGSC (89.8%), and lowest for EC (62.4%). Common misclassifications included MC as EC and EC as HGSC or LGSC. Retraining with additional slides improved balanced accuracy to 85.8% based on single-slide voting and 82.6% based on majority voting. This study highlights the future potential of the AIDA model in classifying epithelial ovarian cancer histotypes. With further refinement to improve performance on more challenging cases, the model could enhance diagnostic accuracy in clinical practice.

Molecular Relationship Between Ovarian Sertoli-Leydig Cell Tumors and Their Heterologous Elements

Since the histogenesis of heterologous elements within Sertoli-Leydig cell tumors (SLCTs) is poorly understood, we aimed to study the molecular relationship between Sertoli cells and the heterologous elements in 16 ovarian SLCTs. We performed a comprehensive molecular study on both SLCT and heterologous components, separately. Eleven tumors (68.7%) had one heterologous element and 5/16 (31.3%) had 2. Heterologous elements were epithelial (7/21 [81%]) (benign mucinous epithelium [9/21, 42.9%], borderline mucinous tumor [1/21, 4.8%], infiltrative mucinous adenocarcinoma [3/21, 14.3%], carcinoid tumor [3/21, 14.3%], and hepatocytes [1/21,4.8%]) or mesenchymal (4/21, 19%) (rhabdomyosarcoma [3/21,14.3%] and chondrosarcoma [1/21, 4.8%]). A DICER1 pathogenic variant was shared between SLCT and the heterologous elements in all cases with interpretable results (15/15), and other common likely-pathogenic/pathogenic variants were shared between SLCTs and heterologous components (3/16, 18.75%), favoring a clonal relationship. In contrast, the identification of distinct variants between components favored a different evolution. The molecular profile of heterologous elements differed from that of their ovarian counterparts occurring without SLCT (eg, mucinous heterologous elements were KRAS wild-type). Chromosome 8 gains, TERT and NRAS/KRAS variants, and absence of fusion transcript, were the hallmark of rhabdomyosarcoma components (3/3, 100%). The progression-free survival rate was significantly shorter for patients with TERT pathogenic variant ( P =0.0029). One patient had pleomorphic Sertoli cells associated with TP53 variants and very poor prognosis with early recurrence after complete initial surgery of a stage IA tumor. These data highlight the biological relationship between SLCTs and their heterologous elements, and the clinical usefulness of identifying pathogenic variants (ie, TERT and TP53 ), although this last point needs to be confirmed in a larger series.

Dominant Negative PTEN Alterations in Endometrial Carcinoma Are Associated With Retained Immunohistochemical PTEN Expression

PTEN immunohistochemistry (IHC) is considered complimentary for assessment of PTEN abnormality in endometrial carcinoma (EC), since PTEN IHC staining pattern does not entirely correlate with the presence and absence of mutations on sequencing. A set of functionally defective PTEN variants with stable protein levels are known to act in a dominant-negative manner to suppress wild-type PTEN activity. Our objective was to evaluate PTEN IHC patterns in ECs with dominant-negative (DN) PTEN mutations. ECs with next-generation sequencing (NGS, using Oncomine Comprehensive Assay v3) over a 3-year period were enrolled. PTEN IHC was scored as loss, subclonal loss, reduced, and intact (the last 3 considered retained). Of 182 EC cases, 114 (62.6%) were identified to have PTEN mutation(s), the majority of endometrioid histotype (87.7%) from all EC molecular classes. Forty-seven cases (41.2%) harbored DN mutations which were of endometrioid (FIGO 1 [n=15, 31.9%], FIGO 2 [n=23, 48.9%], FIGO 3 [n=3, 6.4%]), dedifferentiated (n=2, 4%), carcinosarcoma (n=3, 6%), mixed endometrioid and clear cell carcinoma (n=1, 2%) histotype; with representatives from all molecular classes. PTEN IHC showed retained expression in 95.8% (45/47) of DN-mutated cases (intact staining in 36 [76.6%], reduced staining in 6 [12.5%], and subclonal loss in 3 [6.4%]) cases. Two cases showed loss of expression (4.2%). In the PTEN wild-type group, loss and subclonal loss of expression were seen in 12.5% and 9.4%, respectively. Our results indicate that DN PTEN mutations are common in EC, and are associated with retained IHC staining (intact, reduced, or subclonal loss). These results highlight that IHC and NGS are both required in capturing the full spectrum of PTEN-abnormal EC.

Clinicopathologic and Molecular Analysis of Malignant Neoplasms With Yolk Sac Tumor Differentiation in Women 40 Years of Age and Older

Gynecologic yolk sac tumors (YSTs) are more commonly encountered in children and young women as pure or mixed germ cell tumors and are rarely observed in older women. YSTs in older women are sometimes accompanied by a Müllerian-type carcinoma component, indicating a likely somatic rather than germ-cell origin. Studies of YSTs of germ cell and somatic types in this age group are limited. Analysis of additional pure and mixed tumors with YST differentiation could elucidate differences between these tumor subtypes and the relationship between components in mixed tumors. Clinicopathologic features of 32 malignant neoplasms with YST differentiation in women aged 40+ were analyzed. There were 11 pure YSTs, 7 mixed germ cell tumors, and 14 YSTs with a malignant non-germ cell tumor component (somatically derived yolk sac tumor [SDYST]). Targeted next-generation sequencing (NGS) was performed in 4/11 pure YSTs, 0/7 mixed germ cell tumors, and 4/14 SDYSTs. For the pure YSTs, alterations in DICER1 (1/4), PIK3R1 and PTPRT (1/4), PMS1 (1/4), and TP53 (2/4) were identified. One other pure YST had alterations in PTEN, ARID1A, ARID1B, FGFR2, and CTNNB1 (alterations common in endometrioid carcinoma). SDYSTs demonstrated shared alterations between both components including TP53, KRAS, FBXW7, and KMT2C, suggesting a common origin. The findings in the pure YSTs in older women suggest that for some, the origin could be germ cell as they harbor similar alterations as those described in pure YSTs in young women, whereas in other “pure” YSTs, the molecular profile aligns with previously described SDYSTs, which suggests a SDYST with an unsampled Müllerian carcinoma component rather than a germ cell origin. In SDYSTs, shared alterations are consistent with prior studies and suggest a somatic rather than germ-cell origin.

Comparative Molecular Profiling of “Mixed Endometrioid Adenocarcinoma and Adenosarcoma” of the Uterus and Ovary

“Mixed endometrioid adenocarcinoma and adenosarcoma” is a recently described malignancy of the uterus and ovary characterized by discrete components of Mullerian adenosarcoma and typically low-grade endometrioid adenocarcinoma. Its molecular biology, natural history, and proper classification remain uncertain. We analyzed clinicopathologic data and performed comparative molecular analysis on the adenocarcinomatous and adenosarcomatous components of 14 tumors using a 168-gene next-generation sequencing panel (n=11) and the MSK-IMPACT assay (n=3). Thirteen tumors were stage I, and 1 stage II. The epithelial component was endometrioid carcinoma in 12 (86%), endometrioid intraepithelial neoplasia in 1 (7%), and mesonephric-like adenocarcinoma in 1. The adenosarcomatous component showed sarcomatous overgrowth in 8 (57%), high-grade atypia in 4 (29%), heterologous differentiation in 10 (71%), and lymphovascular invasion in 3 (21%). The adenocarcinomatous and adenosarcomatous components shared molecular alterations in all cases, including mutations in ARID1A (10, 71%), KRAS (8, 57%), DICER1 (7, 50%), PIK3CA (7, 50%), PTEN (6, 43%), and PIK3R1 (4, 29%). Twelve tumors were of no specific molecular profile and 2 were microsatellite instability-high. Four (31%) patients recurred, and 3 (23%) died of disease 7, 8, and 18 months after hysterectomy. Prognosis correlated with high-risk morphologic features in the adenosarcomatous component, including sarcomatous overgrowth, extensive rhabdomyosarcomatous differentiation, vascular invasion, and high-grade nuclear atypia. “Mixed endometrioid adenocarcinoma and adenosarcoma” is a clonal biphasic malignant neoplasm of uncertain histogenesis, with a high frequency of DICER1 mutations.

Uterine Sarcomas Harbouring Novel FOXO1 Gene Rearrangements

Increasing availability and utilisation of high-throughput sequencing techniques has resulted in a rapidly expanding range of uterine mesenchymal lesions harbouring recurrent and nonrecurrent gene rearrangements. Within the literature, 3 molecularly confirmed FOXO1 -rearranged uterine corpus tumors have been reported, all representing alveolar rhabdomyosarcomas (ARMS). We report 5 cases of non-ARMS uterine mesenchymal tumors, in patients aged 36 to 71, harbouring novel FOXO1 rearrangements with different fusion partners ( JRK , PIK3R4, MEIS1 , and ATP7B); in the fifth case, FISH revealed a FOXO1 gene rearrangement with an unknown fusion partner. Although morphologically heterogenous, all 5 cases had a low-grade spindle cell component with 3 cases showing prominent myxoid stroma. Two cases were originally diagnosed as myxoid leiomyosarcoma, one as high-grade endometrial stromal sarcoma, one as an undifferentiated sarcoma with a fibrosarcoma-like appearance, and the other as a myxoid neoplasm of uncertain malignant potential. In 3 cases, the rearrangements showed similar breakpoints to known recurrent FOXO1 gene fusions; 2 rearrangements ( JRK::FOXO1 and MEIS1::FOXO1 ) incorporate both an intact transactivation domain and a DNA-binding domain akin to the rearrangements seen in ARMS, likely representing true oncogenic driver events. Although all 5 cases were confined to the uterine corpus at presentation, recurrences occurred in 2 patients indicating a potential for malignant behaviour and justifying the designation of sarcoma. These cases expand the landscape of FOXO1 -rearranged neoplasms and describe a potential new uterine mesenchymal entity. Further study of additional cases is needed to establish whether these rearrangements truly represent an initiating event for a distinct subset of uterine sarcomas, or whether FOXO1 rearrangements simply represent an additional noninitiating/nondriver event within other established tumor types.

Clinicopathologic and Molecular Characterization of Gynecologic Carcinosarcomas With a Mesonephric-Like Carcinomatous Component

Carcinosarcoma with a mesonephric-like carcinomatous component (MLCS) is a rare subtype of gynecologic malignancy recently described in the literature. This study aims to expand the genomic characterization of MLCS by performing independent molecular analysis of the carcinomatous and sarcomatous components in a series of MLCS. Eight cases of gynecologic MLCS (endometrial, lower uterine segment, and ovarian) were identified and underwent clinicopathologic evaluation. Genomic DNA extraction and next-generation sequencing (NGS) were performed separately from the carcinomatous and sarcomatous components of 4 tumors, while 2 tumors underwent NGS of combined carcinomatous and sarcomatous components. The average age at diagnosis was 65.6 years (range 50 to 83 years). MLCS patients were diagnosed at FIGO stage I (n=3), stage II (n=2), stage III (n=2), and stage IV (n=1). The carcinomatous and sarcomatous components were observed to harbor the same single nucleotide variations. All cases had less than 10 mutations/Mb and were microsatellites stable. All cases (6/6, 100%) harbored KRAS point mutations in codon 12, including the following variants: p.G12D (n=2), p.G12A (n=2), and p.G12V (n=2). Five cases showed additional alterations in ARID1A (case 1), PTEN (case 2), PIK3CA (case 4), SPOP (case 6), TET1 (case 6), BUB1 (case 7), LYN (case 7) and PTPRD (case 7). The presence of both KRAS and PTEN/PIK3CA alterations suggests a combined endometrioid and mesonephric differentiation in MLCS.

Comparison of HER2 Scoring Systems in Endometrial Cancer

Endometrial carcinomas (EC) show variable HER2 protein expression or gene amplification and may be eligible for HER2-directed therapy (trastuzumab or antibody-drug conjugates (ADCs) such as trastuzumab-deruxtecan). HER2 testing is currently recommended in advanced-stage/recurrent serous carcinomas and carcinosarcomas. However, no universally adopted reporting guidelines exist, and institutional practices vary. We aimed to analyze our experience with HER2 testing and compare gynecologic (GyC), gastric (GaC), and breast (BrC) criteria. We identified ECs with available HER2 immunohistochemistry (IHC) and fluorescence in-situ hybridization (FISH) results where applicable. HER2 IHC was reassessed using GyC, GaC, and BrC. The overall HER2-positivity rates were 31% by GyC and BrC, and 35.7% by GaC. The scoring systems significantly differed, with 69.8% concordance between GaC and GyC (P<0.001) and 99.2% concordance between BrC and GyC. Our results emphasize the importance of using the appropriate HER2 scoring criteria depending on the type of intended HER2-directed therapy as well as comprehensive yet perspicuous reporting of HER2 status to ensure optimal clinical outcomes in EC patients.

Pilomatrix-like High-grade Endometrial Carcinoma

Pilomatrix-like high-grade endometrial carcinoma (PiMHEC) is a rare and aggressive variant of endometrial carcinoma often misdiagnosed due to overlapping features with other high-grade malignancies. This study characterizes its clinicopathologic, immunophenotypic, and molecular features to establish key diagnostic criteria and propose a standardized terminology. Ten tumors were analyzed using histopathologic examination, immunohistochemistry, and next-generation sequencing. All but 1 tumor exhibited both low-grade endometrioid and high-grade basaloid components, the latter characterized by either geographic or comedo-type necrosis and shadow cells. Although shadow cells are a hallmark feature, they may be focal or absent, necessitating careful evaluation. High-grade areas consistently showed ER and PR negativity with diffuse nuclear β-catenin staining, correlating with CTNNB1 exon 3 mutations in all tumors. Identical CTNNB1 mutations in spatially distinct tumor components suggest a clonal progression from a low-grade precursor. Additional mutations in ARID1A, PTEN, and PIK3CA were identified. Clinically, PiMHEC exhibited aggressive behavior, with 7 patients experiencing recurrence and 1 succumbing to the disease within 9 months. Metastatic sites included the lungs, liver, lymph nodes, and abdominal wall. PD-L1 expression in 4 tumors suggests potential responsiveness to immune checkpoint inhibitors, whereas low-level HER2 expression (1+ to 2+) in 5 tumors raises the possibility of HER2-targeted therapies. Folate receptor alpha was not expressed in any tumor. In conclusion, PiMHEC is a distinct and highly aggressive endometrial carcinoma with unique histopathologic and molecular features that differentiate it from high-grade endometrioid and other high-grade endometrial cancers including squamous cell carcinoma in rare situations. Its key diagnostic features include high-grade basaloid tumor cells associated with shadow cells, tumor necrosis, and diffuse nuclear β-catenin staining. To improve diagnostic accuracy and reduce ambiguity, we propose adopting “pilomatrix-like high-grade endometrial carcinoma” as a standardized term.

In Response to p53 Immunohistochemical Staining and TP53 Gene Mutations in Endometrial Cancer: Does Null Pattern Correlate With Prognosis?

DICER1-Related Primitive Polyphenotypic Neoplasm

Somatic or germline pathogenic/likely pathogenic variants in DICER1 have known associations with certain neoplasms in the gynecologic tract, including Sertoli-Leydig cell tumors, embryonal rhabdomyosarcoma, and adenosarcoma. However, recent studies have highlighted DICER1- related malignant neoplasms with complex admixtures of sarcomatous, primitive glandular, and/or neuroectodermal elements, which are underrecognized and lack consistent nomenclature. We report the largest series of these primitive polyphenotypic DICER1 -related neoplasms arising in the gynecologic tract or peritoneum. The 15 patients were aged 10 to 77 (median: 37) years. Tumors involved the endometrium (n=6), cervix (n=3), endometrium and cervix (n=2), ovary (n=2), or pelvic peritoneum (n=2). Twelve were organ-confined and 3 were at an advanced stage at presentation. All contained sarcomatous elements composed of sheets and aggregates of ovoid/spindled cells with rhabdomyoblastic differentiation in 13. Periglandular condensation (n=13), cambium layer (n=12), fetal-type cartilage (n=11), and anaplasia (n=4) were also identified. Primitive glands were present in 14 (abundant in 8) and comprised single or clustered simple (n=14) or variably dilated/elongated glands resembling those seen in adenosarcoma (n=9). The epithelium had a primitive appearance with frequent subnuclear vacuoles (n=14), intracytoplasmic granules (n=7), or minimal amphophilic cytoplasm (n=3), and frequently stained for SALL4, glypican-3, and AFP. Neuroectodermal elements were seen in 12, composed of compact small round blue cells punctuated by neuroepithelial tubules. DICER1 alterations were present in all tumors. DICER1 -related primitive polyphenotypic neoplasms present significant diagnostic difficulty due to their varied appearances and lack of consistent nomenclature in the rare reports to date. Recognition of the morphologic features of these unusual neoplasms should prompt confirmatory DICER1 testing and consideration of germline evaluation, particularly in young patients.

Clinicopathologic and Genomic Analysis of Uterine Serous Carcinomas Arising From Endometrial Hyperplasia

Uterine serous carcinoma (USC) typically arises from atrophic endometrium but may be associated with hyperplasia in 5% to 10% of cases. We sought to identify USC with concurrent hyperplasia and (i) define if these are clonally related, and (ii) determine if USC associated with hyperplasia is genetically distinct from USC without hyperplasia. Patients diagnosed with USC and hyperplasia from their hysterectomy specimen between January 1, 2014 and February 29, 2022 were identified. Hyperplasia and carcinoma were separately subjected to tumor-normal panel sequencing. Their repertoire of genetic alterations was compared with that of a separate cohort of atrophy-associated USCs. Of 267 USCs with clinical sequencing and slides available for review, 8 with concurrent carcinoma and hyperplasia had sufficient tissue for molecular studies. In 7 (87.5%) of these 8 cases, USC and hyperplasia were clonally related and shared multiple mutations, including TP53 in 4 cases (57%). In 1 case (USC4), USC and hyperplasia were unrelated at the genetic level, and the hyperplasia was TP53 wild-type. In another case (USC5), USC and TP53 wild-type hyperplasia shared 1 of 11 mutations while being distinct at the copy number level. The prevalence of ARID1A mutations was higher in hyperplasia-associated USC compared with atrophy-associated USC (43% vs. 0%, respectively; P=0.02). USC and co-occurring hyperplasia were clonally related in most cases, commonly harboring TP53 hotspot mutations in both components. These results suggest an alternative origin of tumorigenesis in this rare subset of endometrial cancers.

Targeted RNA Sequencing Highlights a Diverse Genomic and Morphologic Landscape in Low-grade Endometrial Stromal Sarcoma, Including Novel Fusion Genes

Low-grade endometrial stromal sarcoma (LGESS) represents a morphologically and genetically heterogenous mesenchymal neoplasm. Previous work has shown that approximately half of LGESS are characterized by JAZF1::SUZ12 gene fusions, while a smaller proportion involves rearrangement of other genes. However, a subset of cases has no known genetic abnormalities. To better characterize the genomic landscape of LGESS, we interrogated a cohort with targeted RNA sequencing (RNA-Seq). Cases previously diagnosed as low-grade endometrial stromal neoplasia (n=51) were identified and re-reviewed for morphology and subjected to RNA-Seq, of which 47 were successfully sequenced. The median patient age was 49 years (range: 19 to 85). The most commonly detected fusions were JAZF1::SUZ12 (n=26, 55%) and BRD8::PHF1 (n=3, 6%). In addition to the usual/typical LGESS morphology, some JAZF1::SUZ12 fusion tumors showed other morphologies, including fibrous, smooth muscle, sex-cord differentiation, and myxoid change. Novel translocations were identified in 2 cases: MEAF6::PTGR2 and HCFC1::PHF1. Ten tumors (21%) had no identifiable fusion, despite a similar morphology and immunophenotype to fusion-positive cases. This suggests that a subset of cases may be attributable to fusion products among genes that are not covered by the assay, or perhaps altogether different molecular mechanisms. In all, these findings confirm that RNA-Seq is a potentially useful ancillary test in the diagnosis of endometrial stromal neoplasms and highlight their diverse morphology.

Endometrial Carcinomas With Subclonal Loss of Mismatch Repair Proteins

Subclonal loss of mismatch repair (MMR) proteins has been described in a small subset of endometrial carcinomas (ECs), but the genomic basis for this phenomenon has received limited attention. Herein, we retrospectively evaluated all ECs with MMR immunohistochemistry (n=285) for subclonal loss, and in those (n=6), performed a detailed clinicopathologic and genomic comparison of the MMR-deficient and MMR-proficient components. Three tumors were FIGO stage IA, and one each stage IB, II, and IIIC2. Patterns of subclonal loss were as follows: (1) 3 FIGO grade 1 endometrioid carcinomas with subclonal MLH1/PMS2, MLH1 promoter hypermethylation, and no MMR gene mutations; (2) POLE-mutated FIGO grade 3 endometrioid carcinoma with subclonal PMS2, and PMS2 and MSH6 mutations limited to the MMR-deficient component; (3) dedifferentiated carcinoma with subclonal MSH2/MSH6, as well as complete loss of MLH1/PMS2, MLH1 promoter hypermethylation, and PMS2 and MSH6 mutations in both components; (4) dedifferentiated carcinoma with subclonal MSH6, and somatic and germline MSH6 mutations in both components, but with a higher allele frequency in MMR-deficient foci. Recurrences occurred in 2 patients, one consisted of the MMR-proficient component from a FIGO 1 endometrioid carcinoma, while the other was from the MSH6-mutated dedifferentiated endometrioid carcinoma. At the last follow-up (median: 44 mo), 4 patients were alive and disease-free and 2 were alive with disease. In summary, subclonal MMR loss reflects subclonal and often complex genomic and epigenetic alterations, which may have therapeutic implications and therefore must be reported when present. In addition, subclonal loss can occur in both POLE-mutated and Lynch syndrome–associated ECs.

Utility of a PAX2, PTEN, and β-catenin Panel in the Diagnosis of Atypical Hyperplasia/Endometrioid Intraepithelial Neoplasia in Endometrial Polyps

The diagnosis of atypical hyperplasia/endometrioid intraepithelial neoplasm (AH/EIN) within endometrial polyps (EMPs) often poses a diagnostic conundrum. Our previous studies demonstrated that a panel of immunohistochemical (IHC) markers consisting of PAX2, PTEN, and β-catenin can be effectively utilized for the identification of AH/EIN. A total of 105 AH/EIN within EMP were analyzed using the 3-marker panel. We also evaluated these cases for the presence of morules. Benign EMP (n=90) and AH/EIN unassociated with polyp (n=111) served as controls. Aberrant expression of PAX2, PTEN, or β-catenin was observed in AH/EIN in EMP in 64.8%, 39.0%, and 61.9% of cases, respectively. At least 1 IHC marker was abnormal in 92.4% of cases. Overall, 60% of AH/EIN in EMP demonstrated abnormal results for≥2 IHC markers. The prevalence of PAX2 aberrancy was significantly lower in AH/EIN in EMP than in nonpolyp AH/EIN (64.8% vs. 81.1%, P=0.007), but higher than in benign EMP (64.8% vs. 14.4%, P<0.00001). The prevalence of β-catenin aberrancy was significantly higher in AH/EIN in EMP than in nonpolyp AH/EIN (61.9% vs. 47.7%, P=0.037). All control benign EMP demonstrated normal expression of PTEN and β-catenin. Morules were present in 38.1% of AH/EIN in EMP versus 24.3% in nonpolyp AH/EIN, and absent in benign EMP. A strong positive association was found between β-catenin and morules (Φ=0.64). Overall, 90% cases of atypical polypoid adenomyoma (n=6) and mucinous papillary proliferation (n=4) showed IHC marker aberrancy. In conclusion, the 3-marker IHC panel (PAX2, PTEN, and β-catenin) is (1) a useful tool in the diagnosis of AH/EIN in EMP; (2) PAX2 loss should be interpreted with caution and in combination with morphology and other markers.

Uterine Endometrial Stromal Tumors With Pure Low-Grade Morphology Harboring YWHAE::NUTM2 Fusions

Uterine endometrial stromal sarcomas (ESS) with YWHAE::NUTM2 gene fusions are typically morphologically high-grade tumors composed of atypical round cells, sometimes associated with a low-grade fibromyxoid component; they are currently included in the category of high-grade ESS (HGESS). We report 5 morphologically pure low-grade endometrial stromal tumors harboring YWHAE::NUTM2 fusions, including 1 endometrial stromal nodule (ESN) and 4 low-grade endometrial stromal sarcomas (LGESS), an association only occasionally reported previously. Patients ranged from 30 to 51 (mean=43) years and tumors from 4.5 to 7.5 cm (mean=5.7). All were stage I at diagnosis (confined to the uterus). Microscopically, the 4 LGESS showed extensive “tongue-like” invasion of the myometrium, and the ESN was entirely confined to the endometrium with no myometrial invasion. All tumors were composed entirely of morphologically uniform bland ovoid cells resembling proliferative endometrial stroma. A fibromyxoid component was seen in 1 LGESS and the ESN; in the LGESS, this was the sole component. Atypical round cells characteristic of YWHAE::NUTM2 HGESS were not identified. Mitotic count ranged from <1 to 13 per 10 high-power fields (mean: 3). CD10 was positive in 2/4 (focal), estrogen receptor in 5/5 (focal=1; diffuse=4), progesterone receptor in 5/5 (focal=1; diffuse=4) and cyclin D1 was diffusely positive in 3/4. Follow-up was available in all 5 patients and ranged from 6 to 159 months (mean=72). Two patients with LGESS had recurrent disease at 15 and 155 months; 1 showed predominantly LGESS with rare round cells in the initial recurrence and pure HGESS in a subsequent recurrence, while the other patient’s recurrent tumor was predominantly HGESS (90%) in a background of focal fibromyxoid LGESS (10%). Both patients rapidly progressed and died of disease within 5 months of high-grade recurrence. We show that rare cases of morphologically pure low-grade endometrial stromal tumors, some but not all with a fibromyxoid component, harbor YWHAE::NUTM2 fusions and may recur rapidly, with transformation to HGESS and aggressive behavior. Our findings suggest that at least a subset of YWHAE::NUTM2 HGESS evolves from LGESS. We suggest that cyclin D1 and CD10 staining should be performed in all LGESS. Diffuse staining for cyclin D1 and/or negative or focal staining for CD10 should suggest the possibility of a YWHAE::NUTM2 fusion, and appropriate molecular testing should be undertaken. Since no single morphological or immunohistochemical parameter is entirely sensitive for fusion status, we also suggest that testing for a YWHAE::NUTM2 gene fusion should be considered in all cases of LGESS and, if a fusion is present, this should raise the possibility of subsequent high-grade transformation and aggressive behavior, even though such cases should still be categorized as LGESS. Although seemingly rare, ESN and LGESS with YWHAE::NUTM2 fusions may be under-recognized due to a lack of routine fusion testing.

HER2 IHC Expression and Gene Amplification in p53-aberrant High-grade Endometrial Endometrioid Carcinoma Suggests That This Population May Benefit From HER2 Testing and Targeted Therapy

Among gynecologic cancers, uterine serous carcinoma (USC) has been shown to be human epidermal growth factor receptor 2 (HER2) amplified and trastuzumab has been included in the recent National Comprehensive Cancer Network (NCCN) guidelines for treatment of advanced stage or recurrent USC with HER2 overexpression/amplification. There is limited literature suggesting that a subset of high-grade endometrioid carcinomas with aberrant p53 expression may also be HER2 amplified and these patients could benefit from the addition of targeted therapy. We identified 59 p53-aberrant (mismatch repair proficient) FIGO 3 endometrioid carcinomas of the uterus. HER2 immunohistochemistry was performed in all 59 tumors and HER2 fluorescence in situ hybridization (FISH) was performed in 52 of the 59 cases. Four of the 59 cases were HER2 3+ by immunohistochemistry (6.7%), using the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) 2007, 2013, and 2018 criteria. HER2 FISH was performed in 3 of the 4 cases and was amplified in all 3. Nine, 8, and 7 tumors showed 2+ HER2 staining when applying 2018, 2013, and 2007 criteria, respectively, FISH was performed in 7 tumors and none were amplified. An additional 4 cases did not perfectly meet the 2018 ASCO/CAP criteria but were assigned a score of 2+, none were amplified by HER2 FISH. The remaining 42 cases showed 1+ or no staining for HER2, FISH was successfully performed in 38 tumors and none showed amplification. Approximately half of the tumors fulfilled criteria for HER2-low or HER2-very low (10 HER2-low and 20 HER2-very low). Our data shows that a subset of p53-aberrant high-grade endometrial endometrioid carcinoma express HER2 and these patients may benefit from the addition of targeted therapy. The role of targeted therapy in HER2-low gynecologic carcinoma is currently unexplored.

Atypical Placental Site Nodule and Related Lesions

Placental site nodule (PSN) and atypical placental site nodule (APSN) are chorionic-type intermediate trophoblastic lesions, the latter characterized by worrisome histologic characteristics and risk for subsequent trophoblastic neoplasia, mainly epithelioid trophoblastic tumor (ETT). There is no consensus or evidence-based criteria on which and how many features are needed for APSN diagnosis. We assessed interobserver reproducibility of APSN, PSN, and ETT. Five expert pathologists evaluated representative whole slide images (1 hematoxylin-and-eosin and 1 Ki-67/AE1-AE3 immunohistochemical stain) of 50 cases with APSN, PSN, or ETT index diagnosis and recorded independently diagnostic impressions and worrisome histologic characteristics (extensive lesional tissue, severe nuclear atypia, hypercellularity, mitotic activity, irregular borders, tumor necrosis, and Ki-67 index ≥5%). Diagnostic consensus was reached in 96% (agreement of ≥3 experts), and there was agreement with the index diagnosis in 75%. Overall, Fleiss’ kappa score (κ) was 0.46 (highest for PSN [κ=0.58] and lowest for APSN [κ=0.34]). Substantial agreement was reached in evaluating extensive lesional tissue (lesional tissue exceeding normal, κ=0.76) and Ki-67 in the entire lesion (intraclass correlation coefficient=0.62). Most other features showed moderate reproducibility. In cases with a higher degree of agreement, most APSN harbored 3 to 6 worrisome features, while most PSN had <2 and all ETTs had ≥6. In conclusion, APSN diagnosis is challenging, reflected by fair reproducibility among experts. However, agreement was reached in most instances, highlighting the beneficial role of consultation. Criteria refinement may increase reproducibility with the highest agreement of extensive lesional tissue and proliferation in the entire lesion with Ki-67/AE1-AE3. The presence of ≥3 worrisome features might be a reasonable threshold to avoid APSN overdiagnosis.

A Case of a Fumarate Hydratase Deficient Astrocytoma in Association With a Germline Fumarate Hydratase Mutation With Review of the Literature

Diffuse adult-type gliomas are delineated based on their molecular composition including the presence or absence of mutations in isocitrate dehydrogenase 1 or 2 (IDH1/2), a key enzyme in the citric acid cycle. IDH-mutant tumors are associated with better survival than IDH-wildtype counterparts and can be further subdivided into astrocytoma or oligodendroglioma. Rare gliomas with fumarate hydratase (FH) deficiency have been reported. Given that FH is also a critical enzyme in the citric acid cycle, such tumors seem to be epigenetically similar to IDH-mutant tumors and, despite meeting criteria as IDH-wildtype gliomas per the current recommendations set forth by the World Health Organization, may behave in a manner akin to IDH-mutant neoplasms. Hereditary leiomyoma and renal cell cancer syndrome is associated with cutaneous and uterine leiomyomas and renal cell carcinoma caused by a germline FH alteration. To date, only rare examples of patients with known germline FH mutation subsequently diagnosed with a glioma have been reported. We report a case of a young patient with a glioma harboring features of IDH-mutant astrocytoma without evidence of IDH1/2 alterations. After the identification of cutaneous FH-deficient leiomyomas, a retrospective analysis of his brain tumor revealed FH deficiency and a germline FH alteration was ultimately identified after further molecular studies. Although rare, we conclude that FH mutations seem to be part of the spectrum of alterations in diffuse gliomas.

Clinical Significance of Different Histology and High-Risk HPV Types in Neuroendocrine Carcinomas of the Cervix

This study aimed to investigate the impact of different histologic and high-risk (HR) human papillomavirus (HPV) types on the clinicopathologic characteristics and survival of patients with neuroendocrine carcinoma of the cervix (NEC). We retrospectively reviewed the medical records of patients with NEC diagnosed and treated at the Seoul National University Hospital between January 2000 and December 2021. Two pathologists specializing in gynecologic oncology thoroughly examined the slides. To determine the type of HPV infection, microarray analysis and next-generation sequencing were conducted. In addition, the impact of several variables on progressoin-free survival (PFS) and overall survival (OS) was investigated. In total, 47 patients with NEC were included in this analysis. Small-cell neuroendocrine carcinoma (SCNEC) and large-cell neuroendocrine carcinoma (LCNEC) were identified in 36 (76.6%) and 11 (23.4%) patients, respectively. Whereas 31 (66.0%) patients had a pure NEC, 16 (34.0%) were diagnosed with a mixed neuroendocrine non-neuroendocrine neoplasm (MiNEN). Of the 32 NEC patients whose HPV infection status was confirmed, HR-HPV infection was found in 30 of them (93.8%). Nineteen patients were infected with HPV 18. Between patients infected with HPV 16 or 18 and HR-HPV other than 16 or 18, there was no significant difference in most clinicopathologic characteristics such as histology (P=0.311). However, HR-HPV type other than 16 or 18 was associated with pelvic lymph node metastasis (P=0.044) and advanced stage (P=0.035). In the Kaplan-Meier analysis and the Cox regression analyses, no significant difference in PFS and OS was observed between LCNEC and SCNEC, pure NEC and MiNEN, and HPV 16 or 18 and HR-HPV other than 16 or 18. High-risk HPV infection, especially from HPV 18, might play a role and impact on NEC pathogenesis. In this study, we did not find evidence that diverse histology and HR-HPV types affect PFS and OS.

Clinicopathologic Features and Viral Status of Low-risk HPV6 and HPV11-Associated Squamous Cell Carcinoma of the Uterine Cervix and Vulva

Despite being designated as “noncarcinogenic” human papillomavirus (HPV) types, mono-infection with HPV6 or HPV11 has been found in squamous cell carcinomas (SCCs) at specific sites, including the larynx, penis, anus, and rarely, the lower female genital tract. The association between clinicopathologic features, viral status, and the carcinogenic mechanisms related to these low-risk HPVs remains unclear. The current study characterizes a series of low-risk HPV6 and HPV11-associated SCCs of the uterine cervix (6 cases) and vulva (2 cases). The diagnosis of SCC was made through the identification of stromal invasion in 6 cases. In case 2, the diagnosis of cancer was made after metastases to the sigmoid colon and liver. The patient in case 6 was diagnosed with intramucosal papillary SCC given multiple recurrences. While all tumors displayed a similar verruco-papillary architecture, the cytologic features, and immunostaining patterns suggest 2 groups of lesions: one with high-grade cytology and a high Ki-67 proliferation index (>60% of lesional cells), and the other with low-grade cytology and a low Ki-67 (20% to 30% of lesional cells). The detection of HPV6 in 7 of 8 cases underscores its critical role in carcinogenesis at these anatomic sites. Case 8 represented the only patient who was infected with HPV11 and who had a well-controlled human immunodeficiency virus infection. Correlating with viral status, all cases, except case 7, demonstrated a negative or focal p16 staining pattern. In case 7, despite a block pattern of p16 staining often seen in predicting high-risk HPV, we employed several methods to confirm HPV6 as the sole HPV infection. Although this descriptive study does not establish an etiological mechanism for how HPV6/11 leads to malignant transformation, our results exclude the possibility of viral integration through a quantitative polymerase chain reaction-based analysis of the E2/E6 ratio. Our study highlights and expands upon the clinicopathologic features of a distinct group of low-risk HPV6/11-associated SCCs in the cervix and vulva. Although rare, recognizing this group of lesions is important for pathologists and oncologists, as it provides a basis for guiding appropriate prevention strategies and treatment modalities based on the viral type.

Claudin-18 and Mutation Surrogate Immunohistochemistry in Gastric-type Endocervical Lesions and their Differential Diagnoses

Gastric-type endocervical adenocarcinomas (GAS) are aggressive HPV-independent neoplasms with molecular alterations in TP53, STK11, CDKN2A, and SMAD4. Claudin-18 (CLDN18) has emerged as a useful marker to distinguish GAS from HPV-associated neoplasia. Its role in separating GAS from benign proliferations and exuberant endocervical glands is unknown. We studied the utility of immunohistochemistry for CLDN18, progesterone receptor (PR), and mutation surrogate stains (P53, STK11/LKB1, MTAP, SMAD4/DPC4) in 46 GAS, 12 benign gastric-type endocervical lesions, 54 benign Mullerian endocervical populations, and 11 HPV-associated endocervical adenocarcinomas. PD-L1 and HER2 immunostains were evaluated in GAS. Gastric-type lesions were more often positive for CLDN18 (100% benign, 78% GAS, most often well to moderately differentiated) compared to benign Mullerian endocervical specimens (all negative) and HPV-associated neoplasia (18%, always focal). Conversely, PR was negative in all gastric-type lesions and positive in 92% of benign Mullerian endocervical populations. GAS revealed aberrant/mutant expression of P53 in 35%, STK11/LKB1 in 25%, MTAP in 23%, and SMAD4/DPC4 in 9% of cases. Abnormal staining in at least one of these 4 mutation surrogate markers was present in 63% of GAS. HER2 score of 3+ was seen in 25% of GAS, and PD-L1 was positive in 37% based on a combined positive score. CLDN18 is a sensitive and highly specific marker of gastric-type benign and malignant endocervical lesions. Once a gastric-type phenotype is confirmed, mutation surrogate immunostains can be used to support a diagnosis of GAS. PD-L1 and HER2 expression is seen in a subset of GAS offering therapeutic options for this aggressive tumor.

Prospective Fumarate Hydratase Tumor Predisposition Syndrome Screening in Patients With Uterine Smooth Muscle Tumors

Fumarate hydratase tumor predisposition syndrome (FHTPS) is caused by germline fumarate hydratase (FH) pathogenic variants (PVs). Most women with FHTPS develop FH-deficient (FHD) uterine leiomyomas (ULs), which arise 10 to 15 years earlier than aggressive FHD–renal cell carcinoma. We evaluate a previously proposed FHTPS screening strategy for women with ULs. This 5-year, prospective and retrospective study performed FH and later S-(2-succino) cysteine immunohistochemistry (IHC) on all uterine smooth muscle (USM) tumors in patients 40 (later ≤30) years or younger and on all USM tumors with suggestive FHD morphology regardless of age. Patients with FHD tumors by IHC were referred to genetic counseling. Of 840 USM tumors, 112 FHD-tumors by IHC (13%) were identified, all with suggestive FHD-morphology; 44 patients (39%) underwent germline testing, and 15 harbored germline FH PVs (34.1% of germline tested, 13.4% of all FHD-tumors). While FHD tumors were seen across a wide age range (24 to 73 y), those with germline FH PVs were significantly younger (median 33 vs 44 years wild-type, P = 0.0032). Few (12.5%) patients ≥40 and no patients ≥50 had a germline FH PV, whereas a majority (60%) of patients <40 (86% of those <30) had a germline FH PV. We demonstrate that previously proposed resource-conscious screening involving morphology and IHC is effective for identifying women with FHTPS. We provide prospective data confirming patients presenting with FHD-ULs over age 50 are unlikely to harbor germline FH PVs and argue that for germline testing without consideration of other factors, a threshold of younger than 50 years may be appropriate.

Loss of MHC Class I Expression in HPV-associated Cervical and Vulvar Neoplasia

Tumor cell expression of major histocompatibility complex (MHC) class I is required for antigen presentation and adaptive immune recognition. Absent or diminished MHC class I expression is thought to contribute to immunotherapeutic resistance in some epithelial tumors but has not been previously studied in cervical and vulvar carcinoma. Given that anti–programmed cell death 1 (PD-1) checkpoint inhibition is deployed for programmed cell death ligand 1 (PD-L1)-positive recurrent and metastatic cervical squamous carcinomas, identifying tumors with loss of MHC class I is of clinical interest to optimize the selection of immunotherapeutic candidates. Immunohistochemistry for PD-L1 and MHC class I combined A, B, and C heavy chains (MHC class I) was assessed in 58 human papillomavirus–associated cervical and vulvar lesions, including 27 squamous intraepithelial lesions (SILs) and 31 invasive squamous cell carcinoma (SCC). Although 84% of SCC and 22% of SIL were PD-L1-positive, 35.5% (11/31) of SCC and 18.5% (5/27) of SIL also showed clonal or complete loss of MHC class I. Loss of MHC class I expression was more common in PD-L1-positive (10/26, 38%) versus PD-L1-negative SCC (1/5, 20%). In summary, over one third of human papillomavirus–associated cervical and vulvar SCC show clonal or complete loss of MHC class I expression, including many PD-L1-positive cases. This suggests that the efficacy of checkpoint inhibitors targeting the PD-1/PD-L1 axis may be limited in a subset of cervical and vulvar squamous neoplasms due to an impaired ability to engage with the adaptive immune system related to loss of MHC class I expression.

The Spectrum of HPV-independent Penile Intraepithelial Neoplasia

Compared with vulva, precursor lesions of human papillomavirus (HPV)-independent invasive squamous cell carcinoma (SCC) of the penis are insufficiently characterized. We analyzed the histologic and immunohistochemical characteristics of 70 peritumoral precursor lesions and correlated them with the histology and mutational profile of the adjacent HPV-negative invasive penile SCC. Atypical basal keratinocyte proliferation with variously elongated epithelial rete with premature squamatiziation, but regular superficial cornification, termed differentiated penile intraepithelial neoplasia (d-PeIN), were identified adjacent to 42/70 (60%) SCC (36/42 keratinizing (P<0.001); 3 papillary, and 1 each verrucous, clear cell, sarcomatoid SCC). d-PeIN were associated with chronic inflammatory dermatoses (32/42; P<0.001), p53 overexpression (26/42; P<0.001), and hotspot mutations in TP53 (32/42; P<0.001), CDKN2A (26/42; P<0.001) or both (21/42; P=0.003) in the adjacent SCC. Cytoplasmic p16ink4a overexpression in 5/42 d-PeIN correlated with CDKN2A missense mutations in the adjacent SCC. In all, 21/70 (30%) cornified verrucous or glycogenated verruciform precursors with minimal atypia and wild-type p53 (18/21; P<0.001) occurred adjacent to verrucous or papillary SCC (17/21; P<0.001) and keratinizing (4/21) SCC, which harbored mutations in HRAS and/or PIK3CA (12/21; P<0.004). Undifferentiated p16ink4a-negative full-thickness precursors were identified in 7/70 (10%) SCC. Four histologically different HPV-independent penile precursor lesions can be assigned to 2 major genetic/biological pathways with characteristic highly differentiated precursors requiring different clinical management decisions. These include d-PeIN in chronic inflammatory dermatoses, with p53 overexpression and TP53/CDKN2A mutations, and the p53 wild-type verrucous and verruciform precursors unassociated with dermatoses, but with mutations in oncogenes PIK3CA and HRAS.

Pediatric Sertoli-Leydig Cell Tumors of the Ovary

Sertoli-Leydig cell tumors (SLCTs) are currently classified into 3 molecular subtypes: DICER1-mutant (younger patient age), FOXL2-mutant, and DICER1/FOXL2-wildtype. However, it is not clear whether all pediatric SLCTs are DICER1-mutant molecular subtypes and whether other molecular genetic aberrations besides DICER1 are involved in the pathogenesis and prognosis of these tumors. We studied comprehensive data for 8 cases of pediatric SLCTs, including clinicopathological features, pan-cancer–targeted next-generation sequencing/OncoKids panel, and chromosomal microarray analysis, to further analyze the correlation among clinicopathological features, molecular genetic aberrations, and prognosis. The ages of the patients ranged from 4 to 16 years (median, 14 y). Seven cases were moderately differentiated, and one was poorly differentiated with heterologous mesenchymal elements. Two cases had heterologous epithelium or retiform elements. Follow-up was available for all 8 patients (median, 49.5 mo). Seven patients were alive without evidence of recurrence or metastasis, and only case 5 developed metastases (synchronous bilateral pulmonary tumors with rhabdomyosarcomatous differentiation). All 8 tumors were found to harbor somatic hotspot DICER1 mutations, and 5 patients carried germline DICER1 mutations (2 of them had the phenotype of DICER1 syndrome). Together with recent studies, the DICER1 mutation frequency is 100% in pediatric SLCTs (n=27, age≤16 y). Copy number alterations were detected in 3 tumors; the only recurrent copy number alterations was the gain of whole chromosome 6 in case 5 and case 8. This is the first report describing clinicopathological features and molecular alterations in pediatric SLCTs. Our results demonstrate that all pediatric SLCTs belong to the DICER1-mutant molecular subtype, highlighting that somatic hotspot DICER1 mutation detection has high sensitivity (100%) for the auxiliary diagnosis of pediatric SLCTs (age ≤16 y). Some pediatric SLCTs harbor molecular genetic aberrations other than DICER1 mutation, and their significance needs further study.

β-catenin, Pax2, and Pten Panel Identifies Precancers Among Histologically Subdiagnostic Endometrial Lesions

Despite refinements in histologic criteria for the diagnosis of endometrioid precancers, many challenging cases are encountered in daily practice, creating diagnostic uncertainty and suboptimal patient management. Recently, an immunohistochemical 3-marker panel consisting of β-catenin, Pax2, and Pten was identified as a useful diagnostic adjunct. However, previous studies focused either on cancers or diagnostically unambiguous precancers, leaving questions about the applicability and utility of the panel in endometria with architectural features near or below the threshold of accepted histologic criteria for endometrioid precancers. Here, in a retrospective study of 90 patients, we evaluated the performance of the 3-marker panel. Notably, the panel detected a subset of disordered proliferative endometria (8/44, 18%), nonatypical hyperplasias (19/40, 48%), and cases with ambiguous features (3/6, 50%) with aberrancy for ≥1 markers. Marker-aberrant cases were more likely to progress to endometrioid precancer or cancer (P=0.0002). Patterns of marker aberrancy in the index and progressor cases from individual patients provided evidence for origin in a common precursor, and next-generation sequencing of the progressor cases rationalized marker aberrancy for β-catenin and Pten. The results unequivocally demonstrate that some lesions that do not approach current histologic thresholds are bona fide neoplastic precursors with clinically-relevant driver events that can be detected by the 3-marker panel. The findings provide further validation for the diagnostic utility of the panel in clinical practice and its application in difficult or ambiguous cases.

Cytoplasmic Pattern p53 Immunoexpression in Pelvic and Endometrial Carcinomas With TP53 Mutation Involving Nuclear Localization Domains

A cytoplasmic pattern of p53 immunohistochemical expression has recently been reported in a rare subset of pelvic and endometrial cancers with a TP53 mutation involving domains affecting nuclear localization. This study reports the clinicopathologic features of 31 cases with a TP53 mutation involving nuclear localization, the largest study to date, emphasizing practical strategies for recognizing this uncommon variant and distinguishing it from the p53 wild-type pattern. The study also evaluates the prognostic significance of TP53 mutation involving nuclear localization in the ovarian high-grade serous carcinoma (HGSC) cohort of The Cancer Genome Atlas database. Most of the 31 tumors were advanced stage pelvic or endometrial HGSC. All TP53 mutations were predicted to result in loss of function. The p53 overexpression pattern was present in 6 tumors; the p53 null pattern in 3 and the p53 cytoplasmic pattern in 22 tumors. The p53 cytoplasmic pattern predominantly consisted of weak to moderate cytoplasmic staining in >95% of tumor cells as well as variable intensity nuclear staining involving a range of just a few cells to just under 80% of tumor cells. The p53 cytoplasmic pattern was observed in 100% of tumors with TP53 mutation in the nuclear localization domain and in 33% to 44% of tumors with a mutation in the adjacent tetramerization domain or nuclear exclusion sequence (P<0.01). p16 immunoexpression was present in 74% of tumors. In The Cancer Genome Atlas ovarian HGSC cohort, 9% of 471 nonredundant TP53-mutant cases had a nuclear localization domain, tetramerization domain, or nuclear exclusion sequence mutation but there was no significant difference in survival when compared to cases with TP53 mutation outside those domains (P>0.05). p53 cytoplasmic staining merits classification as an aberrant result despite coexisting nuclear staining that in some cases may resemble the p53 wild-type pattern. While positive p16 immunostaining may be of value to confirm diagnostically challenging cases of p53 cytoplasmic staining, a negative result is noninformative and molecular testing for TP53 mutation should be considered, if available.

Morphologic and Molecular Heterogeneity of High-grade Serous Carcinoma Precursor Lesions

Serous tubal intraepithelial carcinoma (STIC) is the fallopian tube precursor lesion for most cases of pelvic high-grade serous carcinoma (HGSC). To date, the morphologic, molecular, and clinical heterogeneity of STIC and a less atypical putative precursor lesion, termed serous tubal intraepithelial lesion, has not been well characterized. Better understanding of precursor heterogeneity could impact the clinical management of women with incidental STICs (without concurrent carcinoma) identified in cases of prophylactic or opportunistic salpingectomy. This study analyzed morphologic and molecular features of 171 STICs and 21 serous tubal intraepithelial lesions. We assessed their histologic features, Ki-67 and p53 staining patterns, and genome-wide DNA copy number alterations. We classified all precursor lesions into 2 morphologic subtypes, one with a flat surface (Flat) and the other characterized by budding, loosely adherent, or detached (BLAD) morphology. On the basis of pathology review by a panel of 8 gynecologic pathologists, we found 87 BLAD, 96 Flat, and 9 indeterminate lesions. As compared with Flat lesions, BLAD lesions were more frequently diagnostic of STIC (P<0.0001) and were found concurrently with HGSC (P<0.0001). BLAD morphology was also characterized by higher Ki-67 proliferation index (P<0.0001), presence of epithelial stratification (P<0.0001), and increased lymphocyte density (P<0.0001). BLAD lesions also exhibited more frequent DNA copy number gain/amplification at the CCNE1 or CMYC loci canonical to HGSCs (P<0.0001). Both BLAD morphology and STIC diagnoses are independent risk factors for an elevated Ki-67 proliferation index. No correlation was observed between BLAD and Flat lesions with respect to patient age, presence of germline BRCA1/2 mutation, or p53 staining pattern. These findings suggest that tubal precursor lesions are morphologically and molecularly heterogeneous, laying the foundation for further studies on the pathogenesis of HGSC initiation and identifying histologic features predictive of poor patient outcomes.

Sclerosis in Sex Cord-Stromal Tumors Other Than the Sclerosing Stromal Tumor

Sclerosis is well-known in sclerosing stromal tumors (SSTs), as its name indicates, but has not been evaluated in other ovarian sex cord-stromal tumors (SCSTs). Its presence in other SCSTs has sporadically caused diagnostic problems in cases we have seen, and this prompted us to review SCSTs with appreciable sclerosis; tumors containing at least 20% sclerosis were included. Seventy cases were identified: 20 thecomas, 20 juvenile granulosa cell tumors (JGCTs), 8 adult granulosa cell tumors (AGCTs), 5 sex cord tumors with annular tubules, 6 retiform Sertoli-Leydig cell tumors (SLCTs; all of the intermediate differentiation), 4 nonretiform SLCTs (3 well-differentiated, 1 of intermediate differentiation with heterologous elements), 4 Sertoli cell tumors, and 3 microcystic stromal tumors (MSTs). Paucicellular sclerotic zones comprised 20% to 95% of the tumors and when conspicuous often obscured diagnostic features. Thirty-one tumors (10 thecomas, 19 JGCTs, 1 AGCT, and 1 MST) showed sclerotic zones focally enveloping nodules of tumor cells, imparting a pseudolobular appearance, and sclerosis often occurred within lobules as well. Ten of these (5 thecomas and 5 JGCTs) also had prominent staghorn blood vessels, generating a low-power appearance focally similar to SST. In 17 tumors, the sclerosis resulted in “compression” of the tumor cells into cords and/or solid tubules. Correct diagnosis in these cases is dependent on careful examination of the cellular zones of the neoplasms, but awareness of the extent of sclerosis that may be seen in diverse SCSTs may be crucial in suggesting the correct diagnosis particularly when the material is limited as in the intraoperative setting. Our findings highlight for the first time the occurrence and character of sclerosis in sex cord tumors other than SSTs and fibromas. Sclerosis is seen in descending proportion of the tumor types as follows: retiform SLCTs, thecomas, MSTs, JGCTs, sex cord tumors with annular tubules, Sertoli cell tumors, AGCTs, and nonretiform SLCTs. Its character can vary somewhat, having particular features in the sex cord tumor with annular tubules (hyaline material within tubules often coalescing and extending beyond the nests to form confluent aggregates) and retiform SLCTs (common in papillary cores).

Incidence and Clinicopathologic Characteristics of Human Papillomavirus–independent Invasive Squamous Cell Carcinomas of the Cervix

We aimed to determine the frequency of human papillomavirus–independent (HPVI) cervical squamous cell carcinoma (SCC) and to describe clinicopathologic characteristics. Among 670 patients with surgically treated SCCs in an established multi-institutional cohort, 447 had available tissue. Tissue microarrays were constructed and studied by in situ hybridization (ISH) for high-risk and low-risk human papillomavirus (HPV) mRNA and immunohistochemistry for p16 and p53. Tumors were HPVI if negative by HPV ISH and they failed to show diffuse p16 positivity by immunohistochemistry, and human papillomavirus–associated (HPVA) if positive by HPV ISH. Ten HPVI SCCs and 435 HPVA SCCs were identified; 2 cases were equivocal and excluded from analysis. The overall rate of HPVI SCC was low (2%) but was higher among older patients (7% in patients above 60 y of age and 17% in patients above 70 y of age). Compared with HPVA, patients with HPVI SCC were significantly older (median age, 72 vs. 49, P<0.001) and diagnosed at a higher stage (40% vs. 18% with stage III/IV disease, P=0.055). p53 expression was varied; 2 cases (20%) had null expression and 8 (80%) had wild-type expression. HPVI SCCs were heterogenous, with keratinizing, nonkeratinizing, and warty morphologies observed. Several cases had a precursor lesion reminiscent of differentiated vulvar intraepithelial neoplasia, with prominent basal atypia and hypereosinophilia or a basaloid-like morphology. Two patients (20%) had distant recurrences within 12 months, and 3 (30%) died of disease during follow-up. HPVI SCCs are rare tumors that are more common among older patients with higher stage disease and have important clinical and histologic differences from HPVA SCCs.

Clinicopathologic Analysis and Molecular Profiling of Ovarian Steroid Cell Tumors

Ovarian steroid and Leydig cell tumors (SCT and LCT, respectively) are rare stromal tumors, with aggressive behavior described in approximately one third of SCTs. Previously reported features potentially predictive of malignancy include size ≥7 cm, gross hemorrhage, necrosis, grade 2 or 3 nuclear atypia, and mitoses ≥2/10 HPFs; however, no subsequent studies have corroborated these findings. Herein, we evaluated a series of 25 tumors (21 SCT, 4 LCT) to explore their clinicopathologic and molecular features. Patients ranged from 16 to 79 years (median: 53 y) and all tumors were FIGO stage I. Recurrences occurred in 3 patients, all of whom died from disease. At least 1 atypical feature was identified in 63% of SCT/LCT and included hemorrhage (n=9), grade 2 or 3 atypia (n=7), mitoses≥2/10 HPFs (n=7), size≥7.0 cm (n=6), and necrosis (n=2); only malignant SCTs demonstrated 4 or 5 atypical features. Next-generation sequencing revealed malignant SCTs were genomically unstable, with uncommon and nonrecurring gene-level alterations (MDM2/CDK4 coamplification, ATRX rearrangement, BAP1 mutation). One SCT with limited follow-up harbored FH and TP53 mutations and occasional arm-level copy number alterations, while all other sequenced tumors (n=7) were genomically stable; 1 had a CTNNB1 mutation and another a CASP10 mutation. In summary, the presence of at least 1 atypical feature is common in SCT/LCT, but most patients demonstrate a benign clinical course. Genomic alterations are infrequent but occur in malignant SCTs as well as a subset of benign SCTs. Molecular analysis of additional malignant SCTs is necessary to identify recurring and/or potentially actionable targets.

Invasive Mucinous Adenocarcinoma of the Lung With a Mural Nodule-like Lesion

Invasive mucinous adenocarcinoma (IMA) of the lung shares some clinicopathological features with mucinous carcinoma of other organs, such as the ovary. Sarcoma-like lesions, called mural nodules, have been reported in the cystic walls of ovarian mucinous tumors. In this study, we analyzed 213 surgically resected cases of IMA of the lung to determine whether similar mural nodule–like lesions were present. We considered abrupt discrete lesions composed of dedifferentiated tumor cells as mural nodule–like lesions. Of 213 IMAs, we identified 11 tumors with mural nodule–like lesions that were histologically categorized into three subtypes similar to those in the ovary. The sarcomatoid and anaplastic carcinoma–like nodules were composed of spindle cell proliferations and polygonal undifferentiated carcinoma, respectively. Sarcoma-like lesions mimicked sarcomatoid nodules, but the spindle cell proliferations were considered a fibroblastic reaction to the scattered, isolated clusters of tumor cells. Molecular analysis of the components of differentiated IMAs and mural nodule–like lesions revealed a clonal relationship, suggesting a spectrum of tumors with different histology. Clinicopathologically, an older age, the male sex, and smokers were significantly associated with IMAs with mural nodule–like lesions. Notably, patient outcomes were unaffected by the presence or absence of these lesions. Our findings demonstrated that IMA of the lung rarely develops mural nodule–like lesions (11 of 213, 5%). Despite a histological impression of clinical aggressiveness, there was no clear trend in patient outcomes, suggesting that pathologists should avoid overstating this mural nodule–like lesion.

Synovial Sarcoma of the Female Genital Tract

Synovial sarcoma most commonly occurs in the extremities but has rarely been described in the female genital tract. In this series, we describe the clinical, morphologic, immunohistochemical, and molecular features of 7 cases of vulvovaginal synovial sarcoma (vulva, n=6; vagina, n=1). We emphasize their wide morphologic spectrum, which can overlap significantly with other more common tumors at these sites, as highlighted by 2 cases initially diagnosed as other entities (endometrioid carcinoma and malignant peripheral nerve sheath tumor). The average patient age was 41 (range: 23 to 62) years and tumor size ranged from 0.8 to 7 cm. Histologically, the tumors were biphasic (n=6) and monophasic (n=1). All cases were confirmed with fluorescence in situ hybridization or sequencing, and 5/5 cases were positive for the novel immunohistochemical markers SSX and SS18-SSX. In 3 cases with follow-up, 2 patients died of disease and 1 was alive with no evidence of disease. Previously described cases arising in the female genital tract are also reviewed. Vulvovaginal monophasic synovial sarcoma raises a broad differential diagnosis, including smooth muscle tumors, spindled carcinomas, and melanoma. Biphasic synovial sarcoma may mimic Müllerian carcinosarcoma, endometrioid carcinoma with spindled, corded, and hyalinized elements, and mesonephric-like adenocarcinoma. Awareness that synovial sarcoma can occur in the female genital tract with a wide variety of histologic appearances is critical for correctly diagnosing this rare entity. In particular, synovial sarcoma should be considered for any deeply situated “adenocarcinoma” in the vulva, with attention to subtle spindle cell differentiation.

Mucinous Tumor Coexisting With Mesonephric-like Proliferation/Tumor in the Ovary

The literature indicates that mesonephric carcinoma (MC) and mesonephric-like adenocarcinoma (MLA) typically lack mucinous and squamous features/differentiation. We report 4 cases of ovarian mucinous tumors (1 mucinous cystadenofibroma and 3 mucinous borderline tumors/atypical proliferative mucinous tumors [MBT/APMT]) co-existing with mesonephric-like lesions which were highlighted by Gata3 and Pax8 expression. All cases contained benign mesonephric-like proliferations (MLP) which focally displayed gastrointestinal-type mucinous metaplasia/differentiation and some were intimately admixed with mucinous glands associated with the mucinous tumor. Metaplastic mucinous epithelium retained expression of Gata3 and Pax8 in some areas while 1 mucinous cystadenofibroma and 1 MBT/APMT were focally positive for Pax8. Along with these mesonephric components, case 1 exhibited features of mesonephric hyperplasia and in 2 cases, 3 and 4, MLA was identified. In case 4, a KRAS c.35G>T (p.Gly12Val) somatic mutation was detected in both the MBT/APMT and the MLA, indicating a clonal origin. This same mutation was also detected in the benign MLP, indicating that it was likely an early genetic event. A CTNNB1 c.98C>T (p.Ser33Phe) somatic mutation, FGFR2 amplification, and CDKN2A/p16 deletion were only detected in the MLA but not in the MBT/APMT. Our result provides evidence to demonstrate the clonal relationship between these morphologically distinct components. Although speculative, we postulate that benign MLPs may give rise to lineage-specific mucinous and mesonephric-like lesions and propose that the MLPs are a new possible origin of some ovarian mucinous tumors. Whether these MLPs arise through transdifferentiation of Müllerian tissue or represent true mesonephric remnants, however, remains largely unknown.

Outcome-based Validation of Confluent/Expansile Versus Infiltrative Pattern Assessment and Growth-based Grading in Ovarian Mucinous Carcinoma

The growth pattern (confluent/expansile versus infiltrative) in primary ovarian mucinous carcinoma (OMC) is prognostically important, and the International Collaboration on Cancer Reporting (ICCR) currently recommends recording the percentage of infiltrative growth in this tumor type. Histologic grading of OMC is controversial with no single approach widely accepted or currently recognized by the World Health Organization Classification of Tumours. Since ovarian carcinoma grade is often considered in clinical decision-making, previous literature has recommended incorporating clinically relevant tumor parameters such as growth pattern into the OMC grade. We herein validate this approach, termed Growth-Based Grade (GBG), in an independent, well-annotated cohort from 2 institutions. OMCs with available histologic material underwent review and grading by Silverberg, International Federation of Obstetrics and Gynecology (FIGO), and GBG schema. GBG categorizes OMCs as low-grade (GBG-LG, confluent/expansile growth, or ≤10% infiltrative invasion) or high-grade (GBG-HG, infiltrative growth in >10% of tumor). The cohort consisted of 74 OMCs, 53 designated as GBG-LG, and 21 as GBG-HG. Using Silverberg grading, the cohort had 42 (57%) grade 1, 28 (38%) grade 2, and 4 (5%) grade 3 OMCs. Using FIGO grading, 50 (68%) OMCs were grade 1, 23 (31%) grade 2, and 1 (1%) grade 3. Follow-up data was available in 68 patients, of which 15 (22%) had cancer recurrence. GBG-HG tumors were far more likely to recur compared with GBG-LG tumors (57% vs. 6%; χ2 P<0.0001). Silverberg and FIGO grading systems also correlated with progression-free survival in univariate analysis, but multivariate analysis showed only GBG to be significant (hazard ratio: 10.9; Cox proportional regression P=0.0004). Seven patients (10%) died of disease, all of whom had GBG-HG (log-rank P<0.0001). Multivariate analysis showed that the percentage of infiltrative growth was the only factor predictive of disease-specific survival (hazard ratio: 25.5, Cox P=0.02). Adding nuclear atypia to GBG categories did not improve prognostication. Our study validates the prognostic value of the GBG system for both disease-free survival and disease-specific survival in OMC, which outperformed Silverberg and FIGO grades in multivariate analysis. Thus, GBG should be the preferred method for tumor grading.

Lobular Carcinoma of the Breast Metastatic to the Ovary

We evaluated the clinicopathologic features of 38 cases of metastatic lobular (n=33) or predominantly lobular (n=5) carcinoma involving the ovary. The patients were from 39 to 91 years of age (mean: 53 y). In 2 cases, the breast primary and ovarian metastasis were diagnosed synchronously, and in 5, the breast primary was only discovered after the metastatic carcinoma in the ovary was found. In the majority of cases (79%), both ovaries were involved; the mean ovarian tumor size was 5.9 cm. The ovarian tumors demonstrated a range of architectural patterns including macronodular (71%), diffuse/solid growth (87%), single-cell infiltration (87%), cords (74%), and small nests/clusters (50%). Nine cases demonstrated focal signet ring cell morphology. The associated stromal reaction ranged from none to marked, with almost half of cases demonstrating a marked stromal response, largely prominent sclerosis. A variety of neoplasms, most typically sex cord-stromal tumors, lymphoma/leukemia, and desmoplastic small round cell tumor, may enter the differential. In addition to the obvious help afforded in most cases by the clinical history, a combination of judicious sampling, particularly to unearth the delicate cords or single-cell growth of lobular carcinoma, appropriate consideration of the cytologic features of the neoplastic cells, and immunohistochemistry can resolve the diverse issues in differential diagnosis that may arise.

Clinical, Morphologic, and Molecular Features Associated With Ovarian Metastases From Pattern A Endocervical Adenocarcinomas

Ovarian metastases from endocervical adenocarcinomas (EAs) are rare but well-described. Silva Pattern A tumors have been reported to pose essentially no risk of lymph node metastases or recurrence. We describe a cohort of patients with Silva Pattern A EAs with ovarian metastases, as well as involvement of other sites. Eight pattern A EAs with ovarian metastases (4 synchronous, 4 metachronous) were identified from our institution’s pathologic archives (2008-2021). Clinicopathologic and molecular features for each case were recorded. All patients were treated by hysterectomy; in each case, the entire tumor was submitted for histologic evaluation. The synchronous metastases were all clinically suspected to be ovarian primary tumors; EAs with metachronous ovarian involvement were confined to the uterus at initial diagnosis, with ovarian metastasis occurring 5 to 171 months after hysterectomy. Morphologically, all tumors were predominantly gland-forming, 5/8 (63%) displayed prominent mucinous differentiation, and 5/8 (63%) involved the corpus. All EAs were either noninvasive (exophytic/papillary/more complex than adenocarcinoma in situ) or showed nondestructive cervical stromal invasion to a depth of 5 mm or less. In the 5 tumors tested by next-generation sequencing, ARID1A, GNAS, and KRAS mutations were detected in 2 (40%), 3 (60%), and 4 (80%) cases, respectively. All 6 patients with follow-up (range, 32 to 181 mo; median, 99.5 mo) had at least 1 recurrence. All but one are without evident disease at last clinical assessment. In an otherwise typical Silva Pattern A EA, corpus involvement, mucinous differentiation, and certain gene mutations may be associated with risk for synchronous or metachronous ovarian metastases.

Malignant Gonadal Germ Cell Tumors (Other Than Pure Germinoma) in Patients With Disorders of Sex Development

We describe 21 nonpure germinomatous gonadal germ cell tumors (9 with a germinoma component), all but 1 associated with gonadoblastoma, in patients with disorders of sex development who ranged from 7 to 36 years old (average, 20 y). Twenty patients were clinically described as phenotypic females with ambiguous genitalia/virilization and primary amenorrhea. The most common documented peripheral karyotype was 46,XY (10/12; 83%). Fifteen of 16 tumors with available clinicopathologic data were unilateral. They ranged from 7 to 30 cm (mean, 15.5 cm) and were solid and cystic with frequent necrosis and hemorrhage. Gonadoblastoma, in its classic (70%), dissecting (5%), or combined (25%) forms, was identified in all but 1. The malignant germ cell tumors were typically mixed except for 5 pure yolk sac tumors and 1 expansile gonadoblastoma with syncytiotrophoblast cells. When admixed, the most common component was yolk sac tumor (n=10), followed by germinoma (n=9), embryonal carcinoma (n=5), choriocarcinoma (n=4), immature teratoma (n=3), and teratoma (n=2). Typical morphologic patterns of yolk sac neoplasia, including reticular/microcystic, solid (including blastema-like), and endodermal sinus (Schiller-Duval bodies), were seen, as well as glandular (n=10) and hepatoid (n=6) differentiation, with cystically dilated glands and diffuse hepatoid morphology in 3 and 2 tumors, respectively. Two yolk sac tumors showed a sarcomatoid pattern. Somatic-type malignancies (alveolar rhabdomyosarcoma and low-grade spindle cell sarcoma, not otherwise specified) were identified in 1 case each. This is the first large series of germ cell tumors other than typical pure germinoma associated with gonadoblastoma. The high frequency of yolk sac tumor with glandular (especially cystic glandular) and hepatoid morphologies is noteworthy, and their presence should prompt further evaluation for an associated gonadoblastoma and possible disorder of sex development.

Yolk Sac Tumor of the Ovary

One hundred fifty yolk sac tumors (YSTs) of the ovary in patients from 1 to 61 (mean: 21.5) years of age are described; 75% of the patients were in the second and third decades and only 1 was above 50 years of age. The clinical manifestations were typically related to a fast-growing adnexal mass; endocrine manifestations (hirsutism) were present in only 2 cases. The tumors were all unilateral and 70% were ≥15 cm; an associated dermoid cyst was present in 20 cases. The tumors were solid and cystic in 57% of the cases, 25% were multicystic, and 18% uniformly solid. The solid tissue was typically tan to pink or yellow and often friable with hemorrhage and necrosis; smaller solid neoplasms were sometime uniformly yellow. The most common histologic pattern was reticular composed of an irregular meshwork of spaces that was conspicuous in 68% of the neoplasms but present to at least a minor degree in all of them. That appearance almost always merged with small to large cysts that were prominent in about 40% of tumors. In 25% of the tumors, cysts sometimes associated with a cellular stroma (the polyvesicular pattern), were present but conspicuous in only half these cases. One third of the tumors had a labyrinthine pattern, 22% glands, and 6% a festoon pattern. Papillae with a central blood vessel (Schiller-Duval bodies) were seen in one-third of the tumors but were numerous in only 5% of them. Nonspecific appearing papillae were seen in 10% of the tumors. A solid growth of cells with pale cytoplasm was seen in one-third of the tumors but was conspicuous in only half of that subset. The solid appearance was typically reminiscent of that of dysgerminoma, but lacked the septa and lymphocytic infiltrate of that neoplasm. Nine tumors had a component of cells with scant cytoplasm resulting in a blastema-like appearance and 3 had cells with abundant clear cytoplasm. Cords and clusters of cells were common but did not dominate the microscopic appearance. The stroma typically had a nonspecific collagenous to edematous appearance. Stromal luteinization was seen in 12 tumors; in 5 this was likely due to the patient being pregnant. Two tumors had minor foci of cells that resembled hepatocytes. Hyaline bodies were seen in most of the tumors and were often conspicuous. The neoplastic cells typically had modest amounts of lightly staining cytoplasm and only mild nuclear pleomorphism. Cells lining cysts were often flattened sometimes resulting in a deceptively innocuous appearance. Many of the tumors (mostly consultation cases), caused diagnostic difficulty; tumors in the differential diagnosis included clear cell carcinoma, embryonal carcinoma, Sertoli-Leydig cell tumor, and juvenile granulosa cell tumor. The patient age and marked elevation of the serum alpha-fetoprotein level (if measured) is helpful in many of these considerations. The overtly malignant gross appearance of most YSTs contrasts with certain other tumors in the differential and the association of some YSTs with dermoid cyst and many clear cell carcinomas with endometriosis may be helpful. The vast majority of ovarian YSTs are dominated microscopically by merging of reticular and cystic patterns which, although focally mimicked by other neoplasms, are in general characteristic, and distinctive features of other neoplasms are absent. Immunohistochemistry, particularly for alpha-fetoprotein and glypican 3, and lack of staining for various markers of other neoplasms is helpful but overlap exists and these results must be considered in the context of the overall clinical, gross, and microscopic features. YSTs dominated by hepatoid and glandular features are rare and their categorization as YSTs should be done cautiously if thoroughly sampled tumors show no evidence of classic features of YST emphasized herein and first elaborated by the Danish investigator Gunnar Teilum whose seminal observations have stood the test of time.

Extrauterine Mesonephric-like Neoplasms

Mesonephric-like adenocarcinomas (MLA) are rare neoplasms arising in the uterine corpus and ovary which have been added to the recent 2020 World Health Organization Classification of Female Genital Tumors. They have similar morphology and immunophenotype and exhibit molecular aberrations similar to cervical mesonephric adenocarcinomas. It is debated as to whether they are of mesonephric or Mullerian origin. We describe the clinical, pathologic, immunohistochemical, and molecular features of 5 cases of extrauterine mesonephric-like proliferations (4 ovary, 1 extraovarian), all with novel and hitherto unreported features. These include an origin of MLA in extraovarian endometriosis, an association of ovarian MLA with high-grade serous carcinoma, mixed germ cell tumor and mature teratoma, and a borderline ovarian endometrioid tumor exhibiting mesonephric differentiation. Four of the cases exhibited a KRAS variant and 3 also a PIK3CA variant. In reporting these cases, we expand on the published tumor types associated with MLA and report for the first time a borderline tumor exhibiting mesonephric differentiation. We show the value of molecular testing in helping to confirm a mesonephric-like lesion and in determining the relationship between the different neoplastic components. We provide further evidence for a Mullerian origin, rather than a true mesonephric origin, in some of these cases. We also speculate that in the 2 cases associated with germ cell neoplasms, the MLA arose out of the germ cell tumor.

Uterine Cervical Sarcoma With a Novel RET-SPECC1L Fusion in an Adult

Independent Validation of Tumor Budding Activity and Cell Nest Size as Determinants of Patient Outcome in Squamous Cell Carcinoma of the Uterine Cervix

A novel 3-tiered grading system that combines tumor budding activity and cell nest size has been found to be highly prognostic in squamous cell carcinomas (SCCs) of various sites, including lung, oral cavity, larynx, hypopharynx, and esophagus. A similar grading system has recently been proposed for SCC of the uterine cervix. In this study, we appraise this grading system in an institutional cohort of cervical SCC to assess its prognostic value in an independent dataset. Our study cohort consisted of 94 consecutive, surgically excised, neoadjuvant therapy-naive cases of SCC of the uterine cervix, stage pT1b or higher. Tumor budding activity and cell nest size were scored on each case, the sum of which formed the basis for assigning a grade in the 3-tiered grading system hereafter referred to as the “tumor budding/nest size” (TBNS) system. As individual variables, both high tumor budding and small nest size were each associated with reduced overall survival (OS), disease-specific survival, and disease-free survival. The full TBNS system was associated with decreased OS, disease-specific survival, and disease-free survival independent of patient age, pathologic stage, and regional lymph node status. TBNS grades 1, 2, and 3 subgroups were clearly distinguishable on multivariate analyses (hazard ratio for OS of 2.06 [95% confidence interval: 0.5-8.42] for grade 2 and 4.58 [95% confidence interval: 1.24-16.87] for grade 3 tumors, relative to their grade 1 counterparts [P=0.035]). Higher grade tumors in the TBNS system were significantly correlated with advanced pathologic stage and lymph node metastasis (P=0.044 and 0.04, respectively). Among the other, potentially prognostic factors, higher pathologic stage, and lymph node metastasis were associated with decreased OS (P<0.001 and 0.004, respectively), whereas keratinization, nuclear size, mitotic count, and World Health Organization (WHO) grade were not. In conclusion, the proposed TBNS grading system is an excellent prognostic indicator that may potentially provide information that is useful in clinical decision-making. Our findings validate the previous study that proposed this system for prognostically stratifying cervical SCC patients. If further confirmed, consideration should be given to routinely adding a TBNS grade to pathologic descriptions of cervical SCC.

Invasive Stratified Mucinous Carcinoma (iSMC) of the Cervix Often Presents With High-risk Features That Are Determinants of Poor Outcome

Invasive stratified mucinous carcinoma (iSMC) has been suggested to represent an aggressive subtype of endocervical adenocarcinoma. We sought to investigate the outcomes of iSMC and determine which clinical and pathologic parameters may influence the prognosis. Slides from 52 cases of iSMC were collected and classified as follows: pure iSMC (>90% of the entire tumor) and iSMC mixed with other human papillomavirus–associated adenocarcinoma components (miSMC) (>10%, but <90% of the entire tumor). Clinical and pathologic parameters were evaluated and compared with overall survival (OS) and recurrence-free survival (RFS). One third of patients with iSMC presented with lymph node metastases (LNM) and 25% developed local recurrences, whereas 4 (7.7%) developed distant recurrences. 29 cases (55.8%) were pure iSMC, whereas 23 cases (44.23%) were miSMC. OS was 74.7% in pure iSMC versus 85.2% in miSMC (P=0.287). RFS was 56.5% in pure iSMC and 72.9% in miSMC (P=0.185). At 5 years, OS in stage I was 88.9% versus stage II to IV 30% (P=0.004), whereas RFS in stage I was 73.9% versus stage II to IV 38.1% (P=0.02). OS was influenced by International Federation of Gynecology and Obstetrics (FIGO) stage (P=0.013), tumor size (P=0.02), LNM (P=0.015), and local recurrence (P=0.022), whereas RFS was influenced by FIGO stage (P=0.031), tumor size (P=0.001), local recurrence (P=0.009), LNM (P=0.008), and type of surgical treatment (P=0.044). iSMC is an aggressive cervical tumor biologically different from other human papillomavirus–associated adenocarcinomas due to the propensity for LNM, local/distant recurrence. FIGO stage, tumor size, LNM, and presence of local/pelvic recurrences are determinants of outcome in iSMCs.

Invasive Stratified Mucin-producing Carcinoma (ISMC) of the Cervix

Invasive stratified mucin-producing carcinoma (ISMC) is a recently described tumor with similar morphology to the stratified mucin-producing intraepithelial lesion. Stratified mucin-producing intraepithelial lesion and ISMC likely arise from human papillomavirus (HPV)-infected reserve cells in the cervical transformation zone that retain their pluripotential ability to differentiate into various architectural and cytologic patterns. This is important, as small studies have suggested that ISMC may be a morphologic pattern associated with more aggressive behavior than usual HPV-associated adenocarcinoma. We sought to study the morphologic spectrum of this entity and its associations with other, more conventional patterns of HPV-associated carcinomas. Full slide sets from 52 cases of ISMC were reviewed by an international panel of gynecologic pathologists and classified according to the new International Endocervical Criteria and Classification system. Tumors were categorized as ISMC if they demonstrated stromal invasion by solid nests of neoplastic cells with at least focal areas of mucin stratified throughout the entire thickness, as opposed to conventional tall columnar cells with luminal gland formation. Tumors comprising pure ISMC, and those mixed with other morphologic patterns, were included in the analysis. Twenty-nine pure ISMCs (56%) and 23 ISMCs mixed with other components (44%) were identified. Other components included 13 cases of usual-type adenocarcinoma, 6 adenosquamous carcinoma, 3 mucinous-type adenocarcinoma, 1 high-grade neuroendocrine carcinoma. ISMC displayed architectural diversity (insular, lumen-forming, solid, papillary, trabecular, micropapillary, single cells) and variable cytologic appearance (eosinophilic cytoplasm, cytoplasmic clearing, histiocytoid features, glassy cell-like features, signet ring-like features, bizarre nuclei, squamoid differentiation). Awareness of the spectrum of morphologies in ISMC is important for accurate and reproducible diagnosis so that future studies to determine the clinical significance of ISMC can be conducted.

Yolk Sac Differentiation in Endometrial Carcinoma

Endometrial somatically derived yolk sac tumors are characterized by yolk sac morphology with AFP, SALL-4, and/or Glypican-3 immunoexpression. Yolk sac marker expression, however, is not limited to tumors with overt yolk sac histology. Three hundred consecutive endometrial malignancies were assessed for immunomarkers of yolk sac differentiation. Of these, 9% expressed ≥1 yolk sac marker, including 29% of high-grade tumors. Only 3 (1%) met morphologic criteria for yolk sac differentiation; these were originally diagnosed as serous, high-grade NOS, and dedifferentiated carcinoma. Two were MMR-intact and comprised exclusively of yolk sac elements, while the dedifferentiated case was MMR deficient and had a background low-grade endometrioid carcinoma; this case also showed BRG1 loss. All 3 were INI1 intact. Nonspecific yolk sac marker expression was seen in 14 carcinosarcomas, 4 endometrioid, 2 serous, 1 clear cell, 1 dedifferentiated, 1 mixed serous/clear cell, and 1 mesonephric-like carcinoma. INI1 was intact in all cases; one showed BRG1 loss. Twenty were MMR-intact, and 4 were MMR deficient. All MMR-deficient cases with yolk sac marker expression, both with and without true yolk sac morphology, had no evidence of residual disease on follow-up, whereas 82% of MMR-intact cases developed recurrent/metastatic disease. In summary, endometrial somatically derived yolk sac tumors were rare but under-recognized. While AFP immunostaining was specific for this diagnosis, Glypican-3 and SALL-4 expression was seen in a variety of other high-grade carcinomas. INI1 loss was not associated with yolk sac morphology or immunomarker expression in the endometrium, and BRG1 loss was rare. All patients with MMR-deficient carcinomas with yolk sac immunoexpression +/− morphology were disease-free on follow-up, whereas the majority of MMR-intact cancers showed aggressive disease.

Cervical Adenocarcinoma

The pattern-based classification system of endocervical adenocarcinoma correlates with nodal metastasis and clinical outcomes, but its application in biopsies is challenging. The aim of this study was the correlation of additional histologic features with patterns of invasion as well as prognosis. A total of 103 specimens from 71 cervical adenocarcinoma cases were studied. Among the 71 cases, all had resection specimens including hysterectomy, cold knife cone excision or loop electrosurgical excision procedure excision, and 32 of these had prior cervical biopsies. We applied the pattern-based classification system to all the specimens and evaluated histopathologic features microscopically. Findings in biopsies were compared with their corresponding resections and correlated with nodal status and disease stage. In 71 resection specimens, pattern A was present in 10 (14.1%), pattern B in 12 (16.9%), and pattern C in 49 (69%) cases. Of the 32 cervical biopsies, pattern of invasion could be classified in only 16 (50%) cases, including 1 (6%) with pattern A, 4 (25%) with pattern B, and 11 (69%) with pattern C. Of the 32 cervical biopsies, 30 could be evaluated for intraluminal necrotic/tumor debris and/or grade 3 nuclei, which correlated with pattern C as well as with lymph node metastasis in the subsequent staging specimens. No tumor with patterns A or B had intraluminal necrotic/tumor debris or grade 3 nuclei in either biopsy or resection specimens. Therefore, intraluminal necrotic/tumor debris and grade 3 nuclei are highly predictive histologic features for cervical adenocarcinomas with pattern C invasion and nodal metastasis.

Interpretation of p16 and p53 in the Classification of Squamous Cell Carcinoma of the Vulva—An Interobserver Agreement Study

Squamous cell carcinoma of the vulva (vSCC) is currently categorized either as human papillomavirus (HPV) associated or independent. Immunohistochemical stains, p16INK4a (p16) and p53 are helpful biomarkers to support the designation of vSCC into 1 of the 3 tumor pathways: (1) HPV-associated, (2) HPV-independent, TP53 mutant, or (3) HPV-independent, TP53 wild type. Recently, a framework of p53 expression patterns in vSCC was proposed. In this international and multi-institutional study, we evaluated the interrater agreement for p53 and p16 and tumor pathway classification in a cohort of 50 invasive vSCC across a variety of practice settings (private practice, academic medicine) and levels of expertise (trainees, gynecologic pathologists, dermatopathologists, private practice pathologists). Our study shows that the overall interrater agreement for the interpretation of p16 in vSCC is strong to near perfect, while the agreement for p53 and tumor pathway assignment is overall moderate. Interrater agreement for p53 and tumor pathway is higher (strong) in the academic practice setting. Pathologists without gynecologic subspecialty expertise benefited the most from a brief educational module, which fostered a better understanding and improved comfort level with the p16/p53 stain interpretation and tumor pathway designation in the diagnosis of vSCC. Some interpretative challenges remain, particularly in regard to select p53 patterns and high-risk HPV-in situ hybridization utilization, warranting additional research.

The Histologic and Molecular Spectrum of Highly Differentiated HPV-independent Cervical Intraepithelial Neoplasia

Recently, the World Health Organization (WHO) recognized the existence of human papillomavirus (HPV)-independent invasive cervical squamous cell carcinoma (SCC), but HPV-independent precursor lesions were not included due to the lack of description of this rare entity. We present the histologic spectrum of highly differentiated squamous HPV-negative and p16ink4a-negative precursor lesions adjacent to and/or preceding invasive HPV-negative cervical SCC in 3 patients. The histologic features resembled those described for vulvar HPV-negative precursor lesions. One precursor featured a proliferation of atypical basal keratinocytes with mitotic activity, premature squamatization in elongated epithelial rete, and mostly regular superficial squamous differentiation with TP53 mutation and immunohistochemical p53 overexpression termed differentiated cervical intraepithelial neoplasia (d-CIN). The other 2 precursors included verruciform acanthosis with plump rete, minimal atypia, and an EGFR mutation that resembled vulvar acanthosis with altered differentiation, and an exophytic papillary proliferation with a PIK3CA mutation resembling the differentiated exophytic vulvar intraepithelial lesion. Two precursors that preceded the invasive SCC harbored an additional pathogenic SMARCB1 mutation. The cytologic smears of d-CIN revealed 3-dimensional branched basaloid tubular structures and eosinophilic squamous cell clusters mimicking the histologic features. In conclusion, highly differentiated cervical HPV-negative precursors are characteristic intraepithelial squamous lesions with somatic mutations that resemble those described in vulvar HPV-independent carcinogenesis. For optimal reproducibility, we propose a simplistic classification of these HPV-negative cervical precursors in TP53-mutated d-CIN and p53 wild-type verruciform intraepithelial neoplasia.

Vulvar Yolk Sac Tumors Are Somatically Derived SMARCB1 (INI-1)-Deficient Neoplasms

So-called primary yolk sac tumors of the vulva are very rare and often have an aggressive disease course. Their molecular features have not been previously characterized. There is also a well-documented group of SMARCB1 (INI-1)-deficient vulvar neoplasms, which includes proximal-type epithelioid sarcoma and myoepithelial carcinoma. Until now, “vulvar yolk sac tumors” and SMARCB1-deficient neoplasms were considered unrelated diseases. After reviewing an index case of a vulvar yolk sac tumor with loss of SMARCB1 by immunohistochemistry, we retrospectively identified 2 additional cases diagnosed as vulvar yolk sac tumors. Patient ages were 34, 32, and 25 years old, and 2 tumors were associated with a pregnancy. All 3 cases showed morphology typical of a yolk sac tumor, and by immunohistochemistry all were positive for SALL4, glypican-3, keratins, and lacked CD34 positivity. All tumors also demonstrated loss of SMARCB1 in tumor cells. Targeted molecular profiling was performed in 2 cases and identified 2 copy deletion of SMARCB1, without genomic alterations typically seen in gonadal yolk sac tumors. In the third case, isochromosome 12p was not identified by fluorescence in situ hybridization. All 3 patients had either local recurrences or distant metastases, and 2 died of disease. One patient had progressive disease while receiving the enhancer of zeste homolog 2 inhibitor tazemetostat. Overall, these findings suggest that vulvar tumors with pure yolk sac-like morphology may represent morphologic variants of SMARCB1-deficient tumors and not veritable germ cell neoplasia. This potential reclassification may have both prognostic and treatment implications and warrants study of additional extragonadal yolk sac tumors.

High-grade Neuroendocrine Carcinomas of the Vulva

Vulvar high-grade neuroendocrine carcinomas (HGNECs) are rare and primarily thought to represent Merkel cell carcinoma (MCC). We present the clinicopathologic features of 16 such cases, the largest series to date. Patients were most often White, postmenopausal, and symptomatic from a palpable vulvar mass/nodule. Tumors ranged from 0.7 to 6 cm and most commonly involved the labium majus. Majority of the cases were pure HGNECs (15/16) with small cell (SC) morphology (14/16); 2 were large cell neuroendocrine carcinomas, of which 1 was combined with moderately differentiated adenocarcinoma. All tumors expressed synaptophysin. Of the 14 HGNECs with SC morphology, 6 were CK20-positive MCCs with characteristic CAM5.2 and neurofilament (NF) expression. Five of these MCCs were positive for Merkel cell polyoma virus large T-antigen (MCPyVLTAg). In contrast, 6 HGNECs with SC morphology were negative for CK20, NF, and MCPyVLTAg and classified as SCNECs. High-risk human papilloma virus was positive in all SCNECs and negative in all MCCs. One case of HGNEC with SC morphology could not be entirely characterized due to lack of tissue for ancillary testing. Five of 12 (42%) cases had a discrepant diagnosis initially rendered. Most patients (10/15) presented with International Federation of Gynecology and Obstetrics stage III or IV disease. Usual sites of metastasis included inguinal lymph node, liver, bone, and lung. Twelve patients underwent surgery with adjuvant chemotherapy and/or radiation therapy, 1 received adjuvant immunotherapy, and 1 patient received neoadjuvant chemotherapy followed by surgery and adjuvant radiation therapy. Median overall survival was 24 months (range: 7 to 103 mo), and overall 5-year survival was 12% (95% confidence interval: 1% to 39%). In summary, vulvar HGNECs are rare, aggressive neoplasms that can be further subclassified into MCC, SCNEC, and large cell neuroendocrine carcinoma. CK20, CAM5.2, NF, TTF-1, MCPyVLTAg, and high-risk human papilloma virus facilitate the distinction of MCC from SCNEC. Proper identification of vulvar HGNECs is critical for patient management.

Immunohistochemical Evaluation of Schlafen 11 (SLFN11) Expression in Cancer in the Search of Biomarker-Informed Treatment Targets

Schlafen 11 (SLFN11), a DNA/RNA helicase, acts as a regulator of cellular response to replicative stress and irreversibly triggers replication block and cell death. Several preclinical in vitro studies and clinical trials established that SLFN11 expression predicts outcomes in patients with advanced cancer treated with DNA-damaging chemotherapeutics and more recently with poly(ADP-ribose) polymerase inhibitors. SLFN11 expression status remains unknown in many cancer types, especially in mesenchymal tumors. This study evaluated a cohort of well characterized 3808 epithelial and 2850 mesenchymal and neuroectodermal tumors for SLFN11 expression using immunohistochemistry. Nuclear SLFN11 expression was rare in some of the most common carcinomas, for example, hepatocellular (1%), prostatic (2%), colorectal (5%), or breast (16%) cancers. In contrast, other epithelial tumors including mesotheliomas (92%), clear cell renal cell carcinomas (79%), small cell lung cancers (76%), squamous cell carcinomas of the tonsil (89%) and larynx (71%), or ovarian serous carcinomas (69%) were mostly SLFN11-positive. Compared with epithelial malignancies, SLFN11 expression was overall higher in neuroectodermal and mesenchymal tumors. Most positive entities included desmoplastic small round cell tumor (100%), Ewing sarcoma (92%), undifferentiated sarcoma (92%), solitary fibrous tumor (91%), dedifferentiated liposarcoma (89%), synovial sarcoma (86%), and malignant peripheral nerve sheath tumor (85%). Also, this study identifies tumors with potentially worse response to DNA-damaging drugs including antibody drug conjugates due to the absence of SLFN11 expression. Such entities may benefit from alternative treatments or strategies to overcome SLFN11 deficiency-related drug resistance. Our approach and results should serve as a foundation for future biomarker-associated clinical trials.

Additional Considerations on Aberrant BRG1 (SMARCA4) Expression in Small Cell Carcinoma of the Ovary, Hypercalcemic Type (SCCOHT)

High-grade Anaplastic Transformation of Ovarian Serous Borderline Tumor

Ovarian serous borderline tumors (SBTs) have a generally favorable prognosis. Although the risk of progression to low-grade serous carcinoma is well documented, progression to high-grade carcinoma is rare. We report the clinicopathologic features of seven SBTs, each associated with the presence of a morphologically unique high-grade component with an extremely dismal prognosis. All of the SBTs exhibited typical hierarchical branching and scattered eosinophilic cells, whereas the high-grade component consisted of a profuse proliferation of epithelioid cells with abundant dense, eosinophilic cytoplasm, variable nuclear pleomorphism, and evident loss of WT1, estrogen receptor, and p16 positivity. In most cases, the SBT demonstrated an abrupt transition to the high-grade component, but one patient initially presented with the usual SBT and developed a recurrent disease that was composed entirely of the high-grade component. Targeted next-generation sequencing revealed identical driver mutations in both the SBT and high-grade components (BRAF in 3, KRAS in 1), confirming clonality. Three cases, in addition, harbored telomerase reverse transcriptase promoter mutations in both components. One case, despite insufficient material for sequencing, was BRAF V600E-positive by immunohistochemistry. Most patients with available follow-up data died within 9 months of diagnosis. This study confirms prior reports of ovarian SBT transformation to high-grade carcinoma and further characterizes a distinct subset with abundant dense eosinophilic cytoplasm and an extremely dismal prognosis. The presence of BRAF mutations in a major subset of these tumors questions the notion that BRAF is associated with senescent eosinophilic cells and improved outcomes in SBT. The role of the additional telomerase reverse transcriptase promoter mutations merits further investigation.

Clear Cell Carcinomas of Müllerian Type and Rete Testis Origin Presenting as Scrotal Masses

Ovarian-type epithelial tumors involving the testis and paratestis are rare, with clear cell carcinomas (CCC) one of the least frequent. We report our experience with 4 müllerian-type (MT) CCCs presenting as testicular/scrotal masses and arising in the paratestis (n=2) and seminal vesicle (n=2; well supported in 1 case and likely in the other). In addition, we document 3 cases of papillary CCC exclusively within the rete testis (RTCCC) and seminiferous tubules and differing from the MT tumors. The patients with MTCCC were 24 to 85 years old (median, 42 y), and 2 had metastases at presentation. The 2 originating in the paratestis were associated with other MT tumors, an endometrioid borderline tumor and a papillary serous borderline tumor. The other 2 MTCCCs likely involved the testis via extension from seminal vesicle primaries through the vasa deferentia. All MTCCCs showed typical features, including tubules, simple papillae with hyalinized cores, and solid nests of polygonal clear cells with occasional hobnail features. Both paratesticular primaries showed sarcomatoid foci with tumor-associated neutrophilic infiltrates. The 3 RTCCCs presented in 54-, 57-, and 60-year-old men as testicular masses; they showed intrarete arborizing papillary growth with nonhyalinized fibrous cores and piled-up, solid foci, lacked hobnail cells, and expressed carbonic anhydrase IX (2/2) and CD10 (2/2) but not CA125, unlike the MTCCCs. On follow-up, 2 patients with MTCCC died of metastatic tumor (4 and 13.5 mo), a third developed ileal and retroperitoneal metastases at 13 months; and the fourth died at 13.5 months of unspecified cause. Follow-up of 2 patients with RTCCCs showed 1 disease free at 8 months and another alive with unknown disease status at 13 years. We conclude that CCCs involving the testis may either be of MT with often aggressive courses or show some features of renal tumors, with confinement to the rete testis and indolent behavior.

Molecular Classification Outperforms Histologic Classification in Prognostication of High-grade Endometrial Carcinomas With Undifferentiated and Sarcomatous Components

Since the establishment of 4 molecular subgroups of endometrial carcinoma (EC), there has been significant interest in understanding molecular classification in the context of histologic features and diagnoses. ECs with undifferentiated, spindle, and/or sarcomatous components represent a diagnostically challenging subset of tumors with overlapping clinical and histologic features. We examined the clinicopathologic, morphologic, immunohistochemical, and molecular features of these tumors identified in our institutions’ pathology databases using immunohistochemistry and targeted sequencing. Disease-specific survival (DSS) and progression-free survival (PFS) were analyzed using Kaplan-Meier curves and log-rank tests. One hundred sixty-two ECs were included: carcinosarcomas (UCS; n=96), dedifferentiated/undifferentiated EC (DDEC/UDEC; n=49), and grade 3 endometrioid EC with spindled growth (GR3spEEC) (n=17). All molecular subgroups were represented in all histologic subtypes and included 12 (7%) POLE-mutated (POLEmut), 43 (27%) mismatch repair-deficient (MMRd), 77 (48%) p53-abnormal (p53abn), and 30 (19%) no specific molecular profile (NSMP) tumors. However, the molecular classification (irrespective of histologic diagnosis) was a significant predictor for both DSS (P=0.008) and P≤0.0001). POLEmut EC showed an excellent prognosis with no recurrences or deaths from the disease. MMRd tumors also showed better outcomes relative to NSMP and p53abn tumors. In conclusion, molecular classification provides better prognostic information than histologic diagnosis for high-grade EC with undifferentiated and sarcomatous components. Our study strongly supports routine molecular classification of these tumors, with emphasis on molecular group, rather than histologic subtyping, in providing prognostication.

High-grade Serous Carcinoma can Show Squamoid Morphology Mimicking True Squamous Differentiation

Tubo-ovarian high-grade serous carcinoma (HG-SC) and ovarian endometrioid carcinoma (EC) can show overlapping morphologic features, such as glandular and solid patterns. The differential diagnosis of these subtypes is thus sometimes difficult. The existence of “squamous differentiation” tends to lead to a diagnosis of EC rather than HG-SC. We noticed that HG-SC can contain a “squamoid component,” but its nature has been poorly investigated. This study was thus established to clarify the nature of this “squamoid component” in HG-SC by investigating its frequency and immunohistochemical features. We reviewed hematoxylin and eosin–stained slides of 237 primary untreated cases of tubo-ovarian HG-SC and identified 16 cases (6.7%) of HG-SC with “squamoid component.” An immunohistochemical staining panel (CK5/6, CK14, CK903, p40, p63, WT1, ER, and PgR) was used to analyze all of these 16 cases. We also selected 14 cases of ovarian EC with “squamous differentiation” as a control. The “squamoid component” in HG-SC was completely p40-negative and showed significantly lower expression of CK5/6, CK14, CK903, and p63 than the “squamous differentiation” in EC. The immunophenotype of the “squamoid component” in HG-SC was concordant with the conventional HG-SC component (WT1-positive/ER-positive). Furthermore, all 16 tumors were confirmed to be truly “HG-SC” by the findings of aberrant p53 staining pattern and/or WT1/p16 positivity, and the lack of mismatch repair deficiency and POLE mutation. In conclusion, HG-SC can on rare occasions show a “squamoid component” mimicking “squamous differentiation.” However, the “squamoid component” in HG-SC does not represent true “squamous differentiation.” The “squamoid component” is one part of the morphologic spectrum of HG-SC, which should be interpreted carefully for the differential diagnosis of HG-SC and EC. An immunohistochemical panel including p40, p53, p16, and WT1 is a useful adjunct to achieve a correct diagnosis.

Genomic Catastrophe (Chromothripsis and Polyploidy) Correlates With Tumor Distribution in Extrauterine High-grade Serous Carcinoma

Most extrauterine high-grade serous carcinomas (HGSCs) are thought to develop first in the distal fallopian tube. Most models of HGSC assume origin from relatively stable, noninvasive serous tubal intraepithelial carcinomas. However, widespread tumor involvement in the absence of a serous tubal intraepithelial carcinoma could occur after catastrophic genomic events (CGEs; such as chromothripsis or polyploidy). Twenty-six HGSCs assigned to fallopian tube (n = 9, group 1) and/or ovary (n = 9, group 2), and primary peritoneal (n = 8, group 3) were assessed by microarray (Oncoscan). CGEs were identified in 15/26 (57.7%); chromothripsis-like pattern in 13/26 (50.0%) and polyploidy in 6/26 (23.1%). CGE was seen in 4/9 (44.4%), 9/9 (100%), and 2/8 (25%) cases in groups 1. 2, and 3, respectively. Overall, CGEs were seen in 9/9 (100%) cases with grossly evident ovarian parenchymal involvement versus 6/17 (35.3%) without (P = 0.0024). Ovarian size (measured on the long axis) correlated with CGE positivity (P = 0.016). CGEs are significantly more common in HGSCs with ovarian parenchymal involvement compared with those limited to the fallopian tube and/or extraovarian tissues. These associations suggest geographically different tumor growth patterns and support the subdivision of HGSCs according to not only the stage but also tumor distribution. They have implications for clinical and pathologic presentation, trajectory of tumor evolution, and in the case of primary peritoneal HGSCs, potentially unique precursors to tumor transitions that could inform or influence cancer prevention efforts.

In Response to Ovarian Sex Cord Tumor Harboring FUS::CREM Fusion: An Ovarian Counterpart of Inflammatory and Nested Testicular Sex Cord Tumor

The CERTAIN Study Results

The Lower Anogenital Squamous Terminology (LAST) Project recommends the use of p16 immunohistochemistry as an adjunct to morphologic assessment of cervical biopsies according to a specific set of criteria. We analyzed the effect of adjunctive p16 according to LAST criteria in a US-based diagnostic utility study involving 70 surgical pathologists providing a total of 38,500 reads on cervical biopsies. Compared with the results obtained using hematoxylin and eosin-stained slides only, including p16-stained slides per LAST criteria increased sensitivity and specificity for diagnosing histologic high-grade squamous intraepithelial lesions across all cases by 8.1% (95% confidence interval [95% CI], 6.5-9.7; P<0.0001) and 3.5% (95% CI, 2.8-4.2; P<0.0001), respectively, using expert consensus diagnoses on hematoxylin and eosin+p16 as reference. Within the subset of cases classified by the pathologists as fulfilling the LAST criteria, adding p16 significantly increased both sensitivity (+11.8%; 95% CI, 9.5-14.0; P<0.0001) and specificity (+9.7%; 95% CI, 7.8-11.5; P<0.0001). However, a comparable improvement in sensitivity (+11.0%; 95% CI, 7.8-14.1; P<0.0001) was found when p16 was used in cases for which p16 staining was not ordered per LAST by the pathologists, whereas specificity decreased by −0.8% (95% CI, −1.1 to −0.5; P<0.0001). The study demonstrates a clinically and statistically significant increase in sensitivity and specificity for high-grade squamous intraepithelial lesion when p16 is used according to LAST criteria. Expanding the use of p16 into non-LAST cases would lead to a comparable improvement in sensitivity within this subgroup of biopsies, at the cost of a minimal, but statistically significant difference in specificity.

Trichorhinophalangeal Syndrome Type 1 Immunohistochemical Expression in Carcinomas of Gynecologic Origin

Trichorhinophalangeal syndrome type 1 (TRPS1) is a new reportedly sensitive and specific immunohistochemical marker for carcinomas of breast origin, including triple-negative (estrogen receptor, progesterone receptor, and HER2) tumors. In our practice, we have observed a subset of cases of nonmammary carcinomas that are positive for TRPS1, with higher frequency in cytology effusion samples with metastatic gynecologic malignancies. This study aimed to evaluate the expression of TRPS1 in a large tissue cohort of Müllerian carcinomas. We retrospectively retrieved 105 cases of formalin-fixed paraffin-embedded gynecologic tumors from our surgical pathology archives. Cases corresponded to tumors of tubo-ovarian (17 high-grade serous carcinomas, 3 low-grade serous carcinomas, 2 clear cell carcinomas, and 8 endometrioid adenocarcinomas), endometrial (25 endometrioid adenocarcinomas, 8 serous carcinomas, 6 clear cell carcinomas, 12 carcinosarcomas, 1 dedifferentiated carcinoma, and 1 mesonephric-like adenocarcinoma), cervical (6 human papillomavirus [HPV]–associated squamous cell carcinomas [SCCs], 11 HPV-associated endocervical adenocarcinomas, and 2 HPV-independent gastric-type endocervical adenocarcinomas), and vulvar (2 HPV-independent SCCs and 1 HPV-associated SCC) origins. Immunohistochemistry for TRPS1 was performed in whole tissue sections and assessed for positivity (≥5% of nuclear labeling), distribution (focal: 5% to 49%, diffuse: 50% to 100%), and intensity (1+, 2+, 3+) in tumor cells. Positive TRPS1 staining was observed in 51.4% (54/105) of cases. Most tumors (64.8%) demonstrated diffuse labeling, while focal in 35.2%. Among positive cases, the intensity was predominantly 1+ (57.4%), followed by 2+ (33.3%) and 3+ (9.2%). Tumors with a high percentage of positivity overall consisted of tubo-ovarian (70%) and endometrial carcinomas (58.4%). TRPS1 immunostain is often expressed in gynecologic carcinomas. Awareness of this phenomenon is crucial when evaluating challenging cases in which the differential diagnosis includes a malignancy of breast origin, to avoid misclassification of the primary site.

Primary Endometrial Gastric (Gastrointestinal)-type Mucinous Adenocarcinoma

Endometrial gastric (gastrointestinal)-type mucinous adenocarcinoma (EmGA) is rare and was introduced as a new entity in the latest World Health Organization (WHO) classification of female genital tumors. Herein, we report a detailed clinicopathologic, immunohistochemical, and molecular study of 27 EmGA, the largest published series to date. The cohort consisted of 27 patients (median age 69 y; range 42 to 87 years). Histologically all cases showed gastric/gastrointestinal differentiation with foamy apical cytoplasm with distinct cell borders (n=21), goblet cells (n=9), signet ring cells (n=4), and Paneth cells (n=1). Using FIGO grading, 5 were grade 1, 14 grade 2, and 8 grade 3. Tumors were positive for MUC6 (10/21), CK7 (22/24), CK20 (16/24), CDX2 (24/26), and Claudin 18 (9/12). In all, 12/27 exhibited aberrant p53 expression and 3/26 showed MLH1 and PMS2 loss, including 2 with confirmed MLH1 gene promoter methylation. Next-generation sequencing showed pathogenic variants in TP53 (13/20), KRAS (7/20), PIK3CA (5/20), BRCA2 (4/20), SMAD4 (3/20), and POLE (1/20). Using TCGA classification (based on cases with available molecular results), 1/20 was POLE mutated, 2/20 were mismatch repair deficient (MMRd), 4/20 were no specific molecular profile (NSMP), and 13/20 were TP53 abnormal. FIGO stage (2009 staging system) ranged from IA to IVB. Outcome data (21 patients; follow-up of 2 to 77 mo) showed that 2 patients died of disease at 14 and 46 months after diagnosis, 1 patient died from other causes at 28 months, 8 were alive with disease, and 10 were alive with no evidence of disease. Like the cervical counterpart, primary EmGA has a distinctive morphologic appearance, harbors frequent TP53 mutations, and can be associated with adverse outcomes despite low-grade morphology and/or low-stage at presentation. They may be represented in all 4 TCGA molecular groups.

Ovarian Sex Cord Tumor Harboring FUS::CREM Fusion

Somatic Sequencing and Microsatellite Instability Results From Mismatch Repair–deficient Endometrial Carcinoma Patients Without Lynch Syndrome (“Lynch-like” tumors)

Immunostaining of endometrial carcinomas for mismatch repair (MMR) protein loss is standard-of-care for Lynch syndrome screening, but also identifies MMR-deficient tumors without germline pathogenic variants. While the majority show MLH1 hypermethylation (MLH1hm), somatic MMR pathogenic variants are increasingly recognized drivers of immunohistochemistry-germline discordance. Because MMR abnormalities with both germline and somatic origins have prognostic significance and impart susceptibility to immune checkpoint inhibitors, it is important to understand how frequently tumors with MMR immunohistochemical loss and normal germline testing (“Lynch-like” tumors) have underlying somatic MMR pathogenic variants. Somatic tumor sequencing±microsatellite instability (MSI) testing was performed on 18 endometrial cancers with MMR immunohistochemical loss but negative MMR germline results and negative MLH1hm where relevant. Tumor sequencing and MSI testing were successful in 94%. Where successful, 80% were MSI-high and 94% had a molecular correlate for the initial immunohistochemical interpretation. The single case without an identified somatic pathogenic variant was MSI-low and initially showed loss of MSH6 by immunohistochemistry but with extremely limited internal control staining. On review, MSH6 immunohistochemistry was reclassified as equivocal, and repeat staining revealed improved control expression with intact MSH6. Following reclassification of this case, 100% tumors with MMR deficiency by immunohistochemistry had at least 1 confirmed somatic MMR pathogenic variant, and 86% were MSI-high. These results demonstrate that when correctly interpreted immunohistochemistry is a strong surrogate for somatic MMR pathogenic variants and support its use as the frontline MMR biomarker in endometrial cancer for heritable screening, molecular prognostic classification, and immunotherapeutic biomarker testing purposes.

Extrauterine Mesonephric-like Carcinoma

Extrauterine mesonephric-like carcinoma (ExUMLC) shares histologic, immunohistochemical (IHC), and molecular (MOL) features with endometrial mesonephric-like carcinoma (EnMLC). Its rarity and histologic overlap with Mullerian carcinomas contribute to underrecognition of ExUMLC. Aggressive behavior of EnMLC is well-documented; behavior of ExUMLC is yet to be characterized. This study presents the clinicopathologic, IHC, and MOL features of 33 ExUMLC identified over a 20-year time period (2002-2022) and compares the behavior of this cohort to more common upper gynecologic Mullerian carcinomas (low-grade endometrioid, LGEC; clear cell, CCC; high-grade serous, HGSC) and EnMLC diagnosed over the same time period. ExUMLC patients ranged from 37 to 74 years old (median=59 y); 13 presented with advanced stage (FIGO III/IV) disease. Most ExUMLC had the characteristic mixture of architectural patterns and cytologic features, as previously described. Two ExUMLC had sarcomatous differentiation, 1 with heterologous rhabdomyosarcoma. Twenty-one ExUMLC (63%) had associated endometriosis, and 7 (21%) arose in a borderline tumor. In 14 (42%) cases, ExUMLC was part of a mixed carcinoma representing >50% of the tumor in 12. Twenty-six cases (79%) were incorrectly classified as follows: LGEC or HGEC (12); adenocarcinoma, not otherwise specified (3); HGSC (3); LGSC (2); mixed carcinoma (1); carcinosarcoma, Mullerian type (2); seromucinous carcinoma (1); transitional pattern of HGSC (1); and female adnexal tumor of probable Wolffian origin (1). Three patients had occult synchronous endometrial LGEC. IHC facilitated diagnosis in all cases with an expression of GATA-3 and/or TTF-1 in conjunction with decreased hormone receptor expression in most tumors. MOL testing (n=20) identified a variety of mutations, most frequently: KRAS (15); TP53 (4); SPOP (4); and PIK3CA (4). ExUMLC and CCC were more likely to be associated with endometriosis (P<0.0001). ExUMLC and HGSC had more recurrences compared with CCC and LGEC (P<0.0001). Histologic subtype was associated with longer disease-free survival for LGEC and CCC versus HGSC and ExUMLC (P<0.001). ExUMLC trended towards a similar poor overall survival as HGSC compared with LGEC and CCC, and EnMLC trended to shorter survival compared with ExUMLC. Neither finding reached significance. No differences were seen between EnMLC and ExUMLC with respect to presenting stage or recurrence. Staging, histotype, and endometriosis were associated with disease-free survival, but on multivariate analysis, only stage remained as an independent predictor of outcome. The tendency of ExUMLC to present at an advanced stage and have distant recurrence points to more aggressive behavior compared with LGEC with which it is most frequently confused, underscoring the importance of an accurate diagnosis.

Mixed Endometrioid Adenocarcinoma and Müllerian Adenosarcoma of the Uterus and Ovary

Mullerian adenosarcoma is a biphasic neoplasm composed of benign or atypical Müllerian epithelium and a malignant mesenchymal component that is usually, but not always, of low grade. Focal architectural or cytologic atypia of the epithelial component resembling atypical hyperplasia may uncommonly be present and foci of adenocarcinoma have been rarely reported. Whether the coexistence of these 2 tumor components is a result of independent primaries (collision tumor), adenocarcinoma arising from the epithelial component of the adenosarcoma, an unusual form of carcinosarcoma or some other mechanism is uncertain. To establish the diagnostic criteria and clinical significance of the coexistence of adenocarcinoma in close association with Müllerian adenosarcoma, we conducted a multi-institutional study of these rare tumors. Twenty-six patients were identified with “mixed” adenosarcoma and adenocarcinoma; they ranged in age from 43 to 87 years (median: 66 y). Tumors occurred in the uterine corpus (n=22), ovary (n=2), and the pelvis (n=2). All but 6 had International Federation of Gynecology and Obstetrics (FIGO) stage I disease. All extrauterine tumors were associated with endometriosis. The tumor size ranged from 2 to 25 cm (median: 7.9 cm). The sarcomatous component was of low grade in 18 and high grade in 8 (the majority demonstrating rhabdomyoblastic differentiation); 9 had stromal overgrowth. Twenty-five carcinomas were endometrioid in type (23 FIGO grade 1; 3 FIGO grade 2) and 1 carcinoma was dedifferentiated with FIGO grade 1 endometrioid adenocarcinoma component; 33% of the uterine neoplasms were associated with adjacent endometrial hyperplasia. Next-generation sequencing in 2 tumors identified similar molecular abnormalities in the sarcomatous and carcinomatous components supporting a clonal relationship. Of 10 patients with available follow-up (median: 18 mo), 8 had no evidence of disease and 2 died of recurrent sarcoma at 7 and 8 months. Endometrioid adenocarcinomas that arise in close spatial association with Müllerian adenosarcoma appear to be clonally related to the sarcoma. Unlike carcinosarcomas, these tumors are usually early stage at presentation. The prognosis appears to be driven by the sarcomatous component. These tumors should be distinguished from carcinosarcomas, dedifferentiated endometrial carcinomas, and corded and hyalinized endometrioid carcinomas.

The 2023 FIGO Staging System for Endometrial Carcinoma

p53 Immunohistochemical Staining and TP53 Gene Mutations in Endometrial Cancer: Does Null Pattern Correlate With Prognosis?

Endometrial/Endometrioid Stromal Tumors With Extensive Whorling and CTNNB1 Translocation

Endometrial/endometrioid stromal tumors are rare and morphologically heterogenous, and their diagnosis may be challenging. We identified 3 endometrial/endometrioid stromal tumors with identical and previously undescribed histologic features and herein report their morphologic, immunohistochemical, and molecular profiles. Patients were 53, 62, and 79 years. Tumors were well-circumscribed, tan-yellow solid masses measuring 10.0, 11.0, and 18.7 cm, and were intramyometrial (n=2) or in the broad ligament (n=1). All showed small, tight whorls of epithelioid to slightly spindled tumor cells with minimal cytoplasm and negligible mitoses, multifocally associated with hyalinization and myxoid change set in a loose fibroblastic background with small, delicate vessels. This morphology was seen throughout in 1 tumor and in ∼20% and 70% of the 2 others with the remaining areas showing sex cord–like differentiation. Tumor cells expressed CD10 (3/3, 1 focal), calretinin (3/3 diffuse), WT1 (3/3 diffuse), estrogen receptor (1/1, diffuse). RNA-sequencing was successful in 1 tumor and revealed a GREB1-CTNNB1 in-frame fusion. All 3 tumors harbored a CTNNB1 translocation by fluorescence in situ hybridization correlating with nuclear β-catenin expression. Whole-genome DNA methylation analysis classified all 3 tumors within the low-grade endometrial stromal sarcoma reference class with flat copy number profiles. One patient (79-y-old) died of unrelated causes 2 months after surgery and the other 2 were alive without disease after 13 and 75 months. We have described a rare subset of endometrial/endometrioid stromal tumors with extensive whorling and a CTNNB1 translocation, expanding the morphologic and molecular spectrum of these neoplasms.

p53 Immunohistochemical Staining and TP53 Gene Mutations in Endometrial Cancer

Whether immunohistochemistry (IHC) of p53 accurately reflects the TP53 mutational status of endometrial carcinoma (EC) has not yet been established. This study aimed to clarify the relationship between p53 IHC and TP53 mutations in EC and to examine whether p53 IHC can be a more convenient prognostic marker than TP53 mutation in EC. We performed p53 IHC staining of EC samples obtained via surgery and genetic analyses using next-generation sequencing. p53 IHC results showed that of the 101 cases, 71 (70%) were wild-type (WT), 12 (12%) were overexpression (OE), and 18 (18%) were in the null group. Missense mutations were found in 9 cases (47.4%) in OE, 2 (10.5%) in null, and 8 (42.1%) in the WT group. Truncating mutations were found in 1 case (8.3%) in OE, 6 (50%) in null, and 5 (41.7%) in the WT group. The 5-year progression-free survival was 0% in OE, 74.8% in null, and 79.0% in the WT group. In the prognosis for each type of TP53 mutation, the 5-year progression-free survival was missense (32.2%), truncating (65.6%), and WT (79.7%). These survival comparisons showed that the p53 IHC OE had the poorest prognosis. These results suggest that the p53 IHC OE is an independent poor prognostic factor for EC and can be used as a simple and rapid surrogate marker for TP53 mutations. Contrastingly, the complete absence of p53 IHC—the null staining pattern—may not accurately predict a TP53 mutation in EC, and it is necessary to be more careful in making the diagnosis of “abnormal.”

Mutation-specific Mismatch Repair–deficient Benign Endometrial Glands in Endometrial Biopsies and Curettings Are a Biomarker of Lynch Syndrome and Associate With Endometrial Carcinoma Development

Endometrial carcinoma is the most common extraintestinal cancer in Lynch syndrome (LS). Recent studies have demonstrated mismatch repair (MMR) deficiency can be detected in benign endometrial glands in LS. We performed MMR immunohistochemistry in benign endometrium from endometrial biopsies and curettings (EMCs) from a study group of 34 confirmed LS patients and a control group of 38 patients without LS who subsequently developed sporadic MLH1-deficient or MMR-proficient endometrial carcinoma. MMR-deficient benign glands were only identified in patients with LS (19/34, 56%) and were not identified in any control group patient (0/38, 0%) (P < 0.001). MMR-deficient benign glands were identified as large, contiguous groups in 18 of 19 cases (95%). MMR-deficient benign glands were identified in patients with germline pathogenic variants in MLH1 (6/8, 75%), MSH6 (7/10, 70%), and MSH2 (6/11, 55%) but not in patients with variants in PMS2 (0/4). MMR-deficient benign glands were seen in all EMC samples (100%) but in only 46% of endometrial biopsy samples (P=0.02). Patients with MMR-deficient benign glands were significantly more likely to have endometrial carcinoma (53%) compared with LS patients with only MMR-proficient glands (13%) (P=0.03). In conclusion, we demonstrated that MMR-deficient benign endometrial glands are frequently identified in EMB/EMC in women with LS and are a specific marker for LS. Women with LS with MMR-deficient benign glands were more likely to have endometrial carcinoma suggesting that MMR-deficient benign glands may be a biomarker of increased risk of endometrial carcinoma development in LS.

GLI1 Gene Alterations in Neoplasms of the Genitourinary and Gynecologic Tract

We report 4 neoplasms of the kidney (2 cases) and uterus (2 cases) harboring rearrangements or amplifications of the GLI1 gene, which because of their unusual clinical presentation, morphology, and immunoprofile mimicked other neoplasms, causing significant diagnostic challenge. The neoplasms occurred in 4 female patients ages 33 to 88 years. Histologically they all demonstrated nodular growth, solid architecture, bland epithelioid to ovoid-spindle cells with pale cytoplasm set in a variably myxoid or hyalinized stroma. One uterine tumor also demonstrated a focal round cell pattern, while another demonstrated focal pleomorphism. Unlike most previously reported neoplasms with these genetic abnormalities, the neoplasms in the current series were negative for S100 protein and minimally reactive for actin. All labeled for CD10 and cyclin D1, while 2 labeled for estrogen receptor and BCOR and 1 labeled for desmin, raising consideration of endometrial stromal sarcoma, myxoid leiomyosarcoma, metastatic breast carcinoma, and glomus tumor. One renal neoplasm demonstrated a GLI1-FOXO4 gene fusion and the other harbored a GLI1 gene rearrangement (unknown partner). The 2 uterine neoplasms exhibited GLI1 gene amplifications. GLI1-altered neoplasms (particularly those with GLI1 amplification) show variable morphology and lack a consistent immunophenotype, and thus may trigger diagnostic challenges which can be resolved by molecular testing.

The Prognostic Values of HPV Genotypes and Tumor PD-L1 Expression in Patients With HPV-associated Endocervical Adenocarcinoma

Despite the well-established pathogenic effect of high-risk human papillomavirus (hrHPV) genotypes on endocervical adenocarcinomas (ECAs), the prognostic values of hrHPV genotypes and their association with other prognostic variables have not been established. We categorized 120 usual-type human papillomavirus–associated (HPVA) ECA cases into 3 species groups (HPV16+, HPV18/45+, and other genotypes+) based on the hrHPV status. The clinical-stage, invasion patterns (Silva), and programmed death ligand-1 (PD-L1) expression were compared among genotype groups. In addition, log-rank test and Kaplan-Meier survival curves were used to compare progression-free survival (PFS) among different patient groups. A total of 120 ECA cases with positive hrHPV tests were included in this study. Among them, 51 (42.5%) were positive for HPV16, 50 (41.7%) were positive for HPV18 or 18/45, 9 (7.5%) were positive for other hrHPV genotypes (not including HPV16/18/45). Our data showed patients had no significant difference in clinical stages (P=0.51), invasion patterns (P=0.55), and PFS (P=0.59) across genotype groups. Overall, a relatively high prevalence of PD-L1 expression was observed in HPVA ECAs (25% by tumor proportion score [TPS] and 55% by a combined positive score [CPS]). Using TPS, 19.6% (10/51) HPV16+ cases, 32.0% (16/50) cases of HPV18 or 18/45+ cases, and 22.2% (2/9) cases of other genotypes+ cases demonstrated PD-L1 positivity. No significant difference in PD-L1 expression was seen across genotype groups (P=0.35). PD-L1 expression in tumors with patterns B and C was significantly higher than in those with pattern A (P=0.00002). Patients with PD-L1-positive tumors by either CPS or TPS showed significantly poorer PFS than those with PD-L1-negative tumors (CPS, P=0.025; TPS, P=0.001). Our data support that HPV genotypes have no prognostic value in HPVA ECAs, while PD-L1 expression serves as a negative prognostic marker in HPVA ECAs and implies an unfavorable outcome.

Molecular Analysis of HPV-independent Primary Endometrial Squamous Cell Carcinoma Reveals TP53 and CDKN2A Comutations

Human papillomavirus (HPV)-independent primary endometrial squamous cell carcinoma (PESCC) is a rare but aggressive subtype of endometrial carcinoma for which little is known about the genomic characteristics. Traditional criteria have restricted the diagnosis of PESCC to cases without any cervical involvement. However, given that modern ancillary techniques can detect HPV and characteristic genetic alterations that should identify the more common mimics in the differential diagnosis, including endometrial endometrioid carcinoma with extensive squamous differentiation and HPV-associated primary cervical squamous cell carcinoma, those criteria may benefit from revision. To further characterize PESCC, we identified 5 cases of pure squamous cell carcinoma dominantly involving the endometrium that had the potential to be PESCC: 1 case involving only the endometrium and 4 cases with some involvement of the cervix. Clinicopathologic features were assessed and immunohistochemical analysis (p16, estrogen receptor, progesterone receptor, and p53), HPV RNA in situ hybridization (high-risk and low-risk cocktails and targeted probes for 16 and 18), and molecular studies were performed. All tumors showed aberrant/mutation-type p53 expression, were negative for estrogen receptor, progesterone receptor, and p16, and had no detectable HPV. Per whole-exome sequencing, 4 of the 5 tumors demonstrated comutations in TP53 and CDKN2A (p16). Four patients died of disease within 20 months (range, 1 to 20 mo; mean, 9 mo), and 1 patient had no evidence of disease at 38 months. PESCC represents a unique, clinically aggressive subtype of endometrial cancer with TP53 and CDKN2A comutations. This characteristic profile, which is similar to HPV-independent squamous cell carcinoma of the vulva, is distinct from endometrioid carcinoma with extensive squamous differentiation and HPV-associated primary cervical squamous cell carcinoma and can be used to distinguish PESCC from those mimics even when cervical involvement is present. Diagnostic criteria for PESCC should be relaxed to allow for cervical involvement when other pathologic features are consistent with, and ancillary techniques are supportive of classification as such.

Morules But Not Squamous Differentiation are a Reliable Indicator of CTNNB1 (β-catenin) Mutations in Endometrial Carcinoma and Precancers

Although collectively regarded as “squamous differentiation (SD)” in endometrial endometrioid carcinoma (EEC) and atypical hyperplasia/endometrioid intraepithelial neoplasia (AH/EIN), morules (often referred to as “squamous morules”) and true SD may represent two distinct phenomena. Here, we explored the distinction between morules versus SD and investigated the association of morules and SD with CTNNB1 mutations. A total of 270 cases of EEC and AH/EIN were studied, including EEC with (n=36) or without (n=36) morules and AH/EIN with (n=80) or without (n=118) morules. Cases were analyzed by immunohistochemistry and selected cases (n=20) by targeted next-generation sequencing panel. Near-perfect agreement was found between morules and glandular β-catenin nuclear staining in AH/EIN and EEC. A strong positive association was found between morules and glandular β-catenin nuclear staining (P<0.0001, Φ=0.59 in AH/EIN; P<0.0001, Φ=0.85 in EEC). There was no association between (1) morules and glandular PAX2 or PTEN aberrant expression or (2) SD and aberrant expression of β-catenin, PAX2 or PTEN (Φ=0.09, β-catenin; Φ=0.16, PAX2; Φ=0.13, PTEN). CTNNB1 mutations were identified in all 20 selected morule-containing cases (100%). Next-generation sequencing was performed on 2 (preprogestin and postprogestin treatment) biopsies from 1 patient, revealing identical mutational profile in morules and glands. In conclusion, (1) SD and morules are distinct biological phenomena; (2) the presence of morules, but not SD, is a reliable indicator of CTNNB1 mutations in EEC and AH/EIN. Our findings demonstrate that SD and morules are distinct biological phenomena. Since morules but not SD are associated with β-catenin mutations, the distinction is clinically relevant and should be included in diagnostic reports.

Recurrent KAT6B/A::KANSL1 Fusions Characterize a Potentially Aggressive Uterine Sarcoma Morphologically Overlapping With Low-grade Endometrial Stromal Sarcoma

With the widespread application of next-generation sequencing, the genetic landscape of uterine mesenchymal neoplasms has been evolving rapidly to include several recently identified fusion genes. Although chromosomal rearrangements involving the 10q22 and 17q21.31 loci have been reported in occasional uterine leiomyomas decades ago, the corresponding KAT6B::KANSL1 fusion has been only recently identified in 2 uterine tumors diagnosed as leiomyoma and leiomyosarcoma. We herein describe 13 uterine stromal neoplasms carrying a KAT6B::KANSL1 (n=11) and KAT6A::KANSL1 (n=2) fusion. Patient ages ranged from 33 to 81 years (median, 49 y). Tumor size was 2.6 to 23.5 cm (median, 8.2 cm). Nine tumors were myometrium-centered, and 3 had an intracavitary component. Original diagnoses were mostly low-grade endometrial stromal sarcoma (LG-ESS; 10 cases) with atypical features (limited CD10 expression, sex cord-like features, pericytic vasculature, and frequent myxoid changes). Treatment was hysterectomy±bilateral salpingo-oophorectomy (10), myomectomy (1), and curettage (2). Five patients were disease-free at 6 to 34 months, 3 (27%) died of disease at 2 to 47 months, and 3 were alive with disease at 2, 17, and 17 years. Histologically, most tumors showed variable overlap with LG-ESS, but they were generally well-circumscribed lacking the extensive permeative and angioinvasive growth typical of LG-ESS. They were composed of monotonous medium-sized oval and spindle cells arranged into diffuse sheets with prominent spiral-type arterioles and frequent pericytoma-like vascular pattern. Variable myxoid stromal changes were frequent. Mitotic activity ranged from 1 to >20 in 10 HPFs. Immunohistochemistry showed variable expression of CD10 (12/13), estrogen receptor (8/11), progesterone receptor (8/11), smooth muscle actin (9/11), desmin (4/12), h-caldesmon (2/10), calretinin (3/8), inhibin (1/7), WT1 (4/7), cyclin D1 (5/11; diffuse in only 1 case), and pankeratin (5/10). This series characterizes a KAT6B/A::KANSL1 fusion-positive uterine stromal neoplasm within the morphologic spectrum of LG-ESS but with atypical features. The relationship of these neoplasms to genuine LG-ESS remains unclear. This molecular subtype of uterine endometrial stromal sarcoma has the potential for an unfavorable clinical course despite the absence of widely invasive growth; nevertheless, analysis of more cases is necessary to delineate the phenotypic spectrum and biological potential of this tumor.

Mesonephric-like Endometrial Carcinoma

Mesonephric-like endometrial carcinoma is a rare but frequently misclassified and aggressive malignancy. KRAS mutations, limited estrogen receptor (ER) expression, and TTF-1, GATA3, and luminal CD10 expression are described in these tumors, but an immunohistochemistry-based screening approach has not been studied. We assessed 300 endometrial carcinomas/carcinosarcomas to ascertain the specificity of TTF-1/GATA3/luminal CD10 expression with or without ER staining for this diagnosis. Next-generation sequencing and morphologic review were performed on screen-positive cases. In all, 3% (9/300) were TTF-1+; 2 coexpressed GATA3. No cases expressed luminal CD10 or GATA3 in isolation. Two TTF-1+/ER− cases, one of which was also GATA3+, were reclassified as mesonephric-like based on morphology and molecular results (KRAS mutations without mismatch repair deficiency, TP53 mutations, or PTEN mutations): these represented 0.7% of all cases (2/300). The reclassified cases were originally diagnosed as grade 1 and 2 endometrioid carcinoma, and the latter had pulmonary metastases and pelvic recurrences. Six TTF-1+ cases retained their original serous (3) and endometrioid (3) diagnoses; 1 was reclassified as dedifferentiated. All had negative or low ER. KRAS mutations were identified in 4 TTF-1+ non–mesonephric-like cases, including 1 serous and 1 grade 3 endometrioid with p53 abnormalities, 1 mismatch repair–deficient endometrioid with a complex molecular profile, and 1 endometrioid with mucinous differentiation. These findings suggest that TTF-1 and ER are good first-line screens for mesonephric-like carcinoma, but caution that a TTF-1+/ER− immunoprofile is not specific, even in the setting of KRAS mutations. A final diagnosis of mesonephric-like carcinoma requires integration of morphologic and immunohistochemical features, with molecular support when relevant.

HER2 Overexpression and Amplification in Uterine Carcinosarcomas With Serous Morphology

Uterine carcinosarcoma (UCS) is an aggressive malignancy with few treatment options. A recent clinical trial has shown an increase in progression-free survival in patients with human epidermal growth factor receptor 2 (HER2)-positive serous endometrial carcinomas treated with anti–HER2-targeted therapies. Few studies have evaluated HER2 expression/amplification in UCS. Similar to serous endometrial carcinoma, the majority of UCS have TP53 mutations and a serous epithelial component, suggesting that UCS may show similar rates of HER2 positivity and therapeutic response. Therefore, we evaluated HER2 expression/amplification in a cohort of UCS over a 5-year period. HER2 immunohistochemistry (IHC) and chromogenic in situ hybridization were performed on tissue microarray and whole tissue sections and scored according to the most recent clinical trial recommendations. Three of 48 UCS (6%) had strong (3+) HER2 IHC expression, and 3 cases (6%) were equivocal (2+). Seven cases (15%) had HER2 amplification by chromogenic in situ hybridization, including all 3 with overexpression and 2 that were equivocal by IHC. Mismatch repair (MMR) protein, p53, and programmed cell death-ligand 1 (PD-L1) expression status was obtained from prior whole section analyses. All HER2-positive cases had a serous morphology and aberrant p53 expression. Only minimal PD-L1 expression was seen in the HER2-positive cases, and none had MMR loss. A subset of UCS with serous morphology have overexpression and/or amplification of HER2, which may predict response to HER2-targeted therapies. HER2-positive UCS may be less susceptible to immune checkpoint inhibition as they uncommonly show MMR deficiency and/or strong PD-L1 expression. Thus, HER2-targeted therapies could be of clinical utility in a subset of UCS without other adjuvant treatment options.

EPM2AIP1 Immunohistochemistry Can Be Used as Surrogate Testing for MLH1 Promoter Methylation in Endometrial Cancer

Immunohistochemical (IHC) evaluation of DNA mismatch repair proteins (MMR) has become routine practice for Lynch syndrome screening and/or part of diagnostic evaluation in endometrial cancer. Approximately 20% to 30% of endometrial carcinomas demonstrate microsatellite instability due to defective DNA MMR. Vast majority of MLH1/PMS2-deficient tumors are sporadic and show MLH1 promoter methylation. MLH1 methylation testing by quantitative polymerase chain reaction-based technique is time, labor, and tissue intensive with an average institutional turnaround time of 2 weeks. MLH1 and EPM2AIP1 genes share a common promoter whose methylation has been shown to affect both genes. We assessed whether IHC for EPM2AIP1 in combination with MMR proteins can serve as surrogate marker for MLH1 promoter methylation status. We performed a retrospective review of all MLH1/PMS2-deficient endometrial carcinomas that underwent MLH1 promoter methylation testing from January 1 to September 31, 2020, at our institution. Microscopic slides were reviewed and EMP2AIP1 IHC was performed. The results were correlated with MLH1 promoter methylation status (percent methylated rate). A total of 119 cases were identified and successfully tested. Nuclear EPM2AIP1 protein expression was observed in benign endometrial cells and myometrial smooth muscle cells. Loss of nuclear EPM2AIP1 staining was identified in 90/110 (81.8%) methylated tumors with additional 14/110 (12.7%) cases showing aberrant staining patterns. Only 6/110 (5.5%) tumors demonstrated intact EPM2AIP1 nuclear expression in presence of MLH1 promoter methylation. EMP2AIP1 IHC is concordant with MLH1 promoter methylation results in 95% of endometrial carcinomas (94.5% sensitivity, 98.1% positive predictive value) and shows promise as a surrogate marker for methylation testing.

Accurate Distinction of Ovarian Clear Cell From Endometrioid Carcinoma Requires Integration of Phenotype, Immunohistochemical Predictions, and Genotype

Ovarian clear cell carcinoma (OCCC) and ovarian endometrioid carcinoma (OEC) are both associated with endometriosis but differ in histologic phenotype, biomarker profile, and survival. Our objectives were to refine immunohistochemical (IHC) panels that help distinguish the histotypes and reassess the prevalence of mismatch repair deficiency (MMRd) in immunohistochemically confirmed OCCC. We selected 8 candidate IHC markers to develop first-line and second-line panels in a training set of 344 OCCC/OEC cases. Interobserver reproducibility of histotype diagnosis was assessed in an independent testing cohort of 100 OCC/OEC initially without and subsequently with IHC. The prevalence of MMRd was evaluated using the testing cohort and an expansion set of 844 ovarian carcinomas. The 2 prototypical combinations (OCCC: Napsin A+/HNF1B diffusely+/PR−; OEC: Napsin A−/HNF1B nondiffuse/PR+) occurred in 75% of cases and were 100% specific. A second-line panel (ELAPOR1, AMACR, CDX2) predicted the remaining cases with 83% accuracy. Integration of IHC improved interobserver reproducibility (κ=0.778 vs. 0.882, P<0.0001). The prevalence of MMRd was highest in OEC (11.5%, 44/383), lower in OCCC (1.7%, 5/297), and high-grade serous carcinomas (0.7%, 5/699), and absent in mucinous (0/126) and low-grade serous carcinomas (0/50). All 5 MMRd OCCC were probable Lynch syndrome cases with prototypical IHC profile but ambiguous morphologic features: 3/5 with microcystic architecture and 2/5 with intratumoral stromal inflammation. Integration of first-line and second-line IHC panels increases diagnostic precision and enhances prognostication and triaging for predisposing/predictive molecular biomarker testing. Our data support universal Lynch syndrome screening in all patients with OEC when the diagnosis of other histotypes has been vigorously excluded.

Corded and Hyalinized and Spindled Endometrioid Endometrial Carcinoma

Corded and hyalinized and spindled carcinomas are rare variants of endometrioid carcinoma (EC) characterized by cords of low-grade epithelial cells (±spindle cells) within a hyalinized stroma or spindled epithelial cells, respectively, that merge with conventional low-grade EC. Due to their “biphasic” morphology, these tumors are often misdiagnosed as carcinosarcoma. The clinicopathologic features including mismatch repair protein (PMS2 and MSH6) and p53 immunohistochemical expression and POLE mutational status of 9 corded and hyalinized and spindled endometrial ECs were evaluated and classified into The Cancer Genome Atlas (TCGA) based molecular subgroups. Beta-catenin immunohistochemistry was performed as a surrogate for CTNNB1 mutational status. The mean age at diagnosis was 49 years (range: 34 to 68 y) with staging information available for 6 patients: stage IA (n=1), stage IB (n=1), stage II (n=2), stage IIIA (n=1), stage IIIC1 (n=1). A prominent corded and hyalinized component was present in 7 ECs comprising 15% to 80% of the tumor with a minor (5% to 15%) spindled morphology in 5. Two additional tumors were composed of a low-grade spindled component comprising 25% to 30% of the neoplasm. Tumors were grade 1 (n=3), grade 2 (n=5), and grade 2 to 3 (n=1) and squamous differentiation was identified in 8/9. All tumors had preserved expression of mismatch repair proteins with 8 showing a p53 wild-type phenotype including the grade 2 to 3 EC; 1 grade 2, stage IB tumor exhibited a mutant pattern of expression. All (n=7) but 1 tumor demonstrated nuclear beta-catenin expression in the glandular, squamous, and corded or spindled components. POLE exonuclease domain mutations were absent in all tumors. Based on our findings, corded and hyalinized EC and EC with spindle cells are usually low grade, low stage, and present at a younger age and exhibit squamous differentiation at an increased frequency compared to typical EC. Unlike carcinosarcomas, which frequently harbor TP53 mutations, these tumors usually exhibit wild-type p53 and nuclear beta-catenin expression, indicative of underlying CTNNB1 mutations. According to the TCGA subgroups of endometrial carcinoma, the majority of corded and hyalinized and spindled EC appear to fall into the copy number low (“no specific molecular profile”) subgroup.

Atypical Endometrial Hyperplasia, Low-grade

Atypical endometrial hyperplasia (AEH) is considered a precursor of endometrioid carcinoma. The 2020 World Health Organization (WHO) classification divides endometrial hyperplasia into 2 categories: hyperplasia without atypia and atypical hyperplasia/endometrioid intraepithelial neoplasia (EIN); however, this classification does not consider the degree of nuclear atypia. We graded nuclear atypia for estimating the risk of finding carcinoma at hysterectomy. Also, we investigated genes involved in endometrial carcinogenesis including mismatch repair (MMR) genes and ARID1A, PIK3CA, PTEN, KRAS, and CTNNB1. We reviewed 79 biopsies of AEH from 79 patients who underwent hysterectomy within a 1-year interval. Intraobserver and interobserver agreement of grading nuclear atypia and the relationship between the grade of nuclear atypia at biopsy and the findings at hysterectomy were evaluated. Immunohistochemistry for MMR status was performed in all cases and targeted sequencing in 11. Using low-grade versus high-grade nuclear atypia, κ values ranged from 0.74 to 0.91 (89% to 96%) and from 0.72 to 0.81 (87% to 91%) for the intraobserver and the interobserver agreement, respectively. The degree of nuclear atypia at biopsy was highly predictive of the findings at hysterectomy (P=1.6×10−15). Of 53 patients with low-grade AEH, none had carcinoma at hysterectomy, whereas 6 (6/26; 23%) with high-grade AEH in the biopsy also had high-grade AEH in the uterus and 16 (16/26; 61%) had FIGO grade 1 carcinoma. MMR deficiency was found in 3 of the 79 patients. None of the genes showed a mutational load significantly associated with the degree of nuclear atypia. In summary, our data show high reproducibility within and between observers for the diagnosis of low-grade and high-grade AEH. Most cases of AEH had low-grade nuclear atypia and neither high-grade AEH nor carcinoma was encountered in the corresponding hysterectomy specimens.

HER-2 Amplification in Uterine Serous Carcinoma and Serous Endometrial Intraepithelial Carcinoma

Human epidermal growth factor receptor 2 (HER-2) targeted therapy shows promising results in HER-2-positive uterine serous carcinoma (USC). HER-2 scoring criteria for USC and its associated noninvasive lesion, serous endometrial intraepithelial carcinoma (SEIC), are not well-established. Here, we compare the breast and gastric (GI) HER-2 immunohistochemistry (IHC) scoring criteria for HER-2 with HER-2/neu fluorescence in situ hybridization (FISH) in 68 tumors (17 USC with SEIC, 30 USC, 18 SEIC, 3 metastatic USC). The majority (97%) of lesions displayed intratumoral HER-2 IHC heterogeneity. Breast or GI IHC scoring criteria were performed equivalently. The breast and GI IHC criteria classified 51% and 47% USC as HER-2 negative (IHC 0/1+), 40% and 45% as equivocal (IHC 2+), and 9% each as HER-2 positive (IHC 3+). A quarter of USC classified as HER-2 negative or positive with the breast (25%, n=7/28) or GI IHC criteria (23%, n=6/26) was discordant by FISH. Specifically, 13% to 14% of IHC 0/1+ USC were FISH amplified; 50% of IHC 3+ USC were FISH negative. The majority (77% to 83%) of SEIC were HER-2 IHC 0/1+, and no SEIC was HER-2 IHC 3+. A minority (4% to 7%) of IHC 0/1+ SEIC were FISH positive. Discordant HER-2 status was observed between half (47%,bn=7/15) of synchronous SEIC and USC. In conclusion, USC displays HER-2 intratumoral heterogeneity, a high IHC/FISH discordance rate, and variation in HER-2 status between the SEIC and invasive components. Caution is required when evaluating HER-2 in small biopsies, which should be repeated on excisions. Both IHC and FISH should be performed on USC until clinical trials correlate HER-2 status with clinical response to HER-2-targeted therapy.

Endometrial Gastric-type Carcinoma

Clinicopathologic Characteristics of Mesonephric Adenocarcinomas and Mesonephric-like Adenocarcinomas in the Gynecologic Tract

Mesonephric adenocarcinoma (MA) and mesonephric-like adenocarcinoma (MLA) are uncommon neoplasms of the gynecologic tract that have until recently been poorly understood. Although their morphologic, immunohistochemical, and molecular profiles have been recently defined, little is known about their clinical behavior. Small studies have demonstrated inconsistent findings and no large studies have examined the clinical behavior of these adenocarcinomas. In this multi-institutional study, representing the largest and most stringently defined cohort of cases to date, we examined the clinicopathologic features of 99 MAs and MLAs (30 MAs of the uterine cervix, 44 MLAs of the endometrium, and 25 MLAs of the ovary). Only tumors with characteristic mesonephric morphology and either immunohistochemical or molecular support were included. Our results demonstrate that the majority of mesonephric neoplasms presented at an advanced stage (II to IV) (15/25 [60%] MA of the cervix, 25/43 [58%] MLA of the endometrium, and 7/18 [39%] MLA of the ovary). The majority (46/89 [52%] overall, 12/24 [50%] MA of the cervix, 24/41 [59%] MLA of the endometrium, and 10/24 [42%] MLA of the ovary) developed recurrences, most commonly distant (9/12 [75%] MA of the cervix, 22/24 [92%] MLA of the endometrium, and 5/9 [56%] MLA of the ovary). The 5-year disease-specific survival was 74% (n=26) for MA of cervix, 72% (n=43) for MLA of endometrium, and 71% (n=23) for MLA of ovary. Our results confirm that mesonephric neoplasms are a clinically aggressive group of gynecologic carcinomas that typically present at an advanced stage, with a predilection for pulmonary recurrence.

Molecularly Classified Uterine FIGO Grade 3 Endometrioid Carcinomas Show Distinctive Clinical Outcomes But Overlapping Morphologic Features

FIGO grade 3 endometrioid endometrial carcinoma (EEC) is a heterogenous group of tumors with variable molecular and clinicopathologic characteristics but is treated clinically as a single entity. There is a need for additional objective markers to help guide management. The aim of this study was to evaluate a cohort of FIGO grade 3 EEC to validate the prognostic impact of molecular classification using POLE mutation (POLE-mut) analysis and immunohistochemistry for p53 and mismatch repair proteins. A secondary aim was to assess for any morphologic or immunophenotypic correlates among the molecular groups. Ninety-five cases of FIGO grade 3 EEC who underwent a hysterectomy at our institution were identified. Ten tumors (11%) harbored POLE-mut, 35 tumors (37%) showed mismatch repair deficiency, 18 tumors (19%) showed aberrant p53 staining (p53-ab), and 26 cases (27%) lacked all of these findings and were classified as no specific molecular profile. Six separate cases harbored >1 abnormality (multiple classifier), 5 of which had POLE-mut. The POLE-mut group and multiple classifier group showed excellent clinical outcomes, the p53-ab group showed the worst clinical outcomes and the 2 remaining groups showed intermediate prognosis. While the POLE-mut tumors showed a statistically significant enrichment for morphologic features including serous-like atypia and lymphocytic infiltrates, these findings were seen across all 4 molecular groups. There was no correlation between molecular grouping and tumor immunophenotypic findings, but overall 18% and 24% of tumors were completely negative for PAX-8 and estrogen receptor, respectively. Five CTNNB1 mutations were identified, 3 of which occurred in the context of a POLE-mut (including 1 multiple classifier case with MLH1/PMS2 loss). Thus our study corroborates the prognostic impact of molecular classification of high-grade endometrioid carcinoma of the uterus, achieved by readily available immunohistochemical stains in addition to POLE-mut analysis.