Human Pathology

Female reproductive tract inflammatory myofibroblastic tumor (IMT): A comprehensive analysis of clinicopathological and genomic features in a case series, including the identification of SERPINE1-ALK fusion in the fallopian tube

Inflammatory myofibroblastic tumors (IMTs) of the female reproductive tract are rare neoplasms, predominantly originating in the uterus, but can occasionally be identified in other locations. This retrospective study included 15 cases from six hospitals in China between 2017 and 2024, comprising 14 cases involving the uterus and one involving a fallopian tube. DNA and RNA next-generation sequencing (NGS) was conducted on all samples. The age of onset ranged from 34 to 54 years, with a median of 41 years and a mean of 42.40 ± 1.32 years. Tumor sizes varied from 2.9 cm to 10.0 cm, with a median size of 6.00 cm and a mean size of 5.90 ± 0.45 cm. RNA sequencing demonstrated ALK rearrangements with either identical or distinct fusion partners in individual cases, including a new partner, SERPINE1, detected in the case involving the fallopian tube. DNA sequencing revealed that 46.7 % (7/15) of the cases exhibited additional gene mutations, including one case with a TP53 mutation that had been previously reported and subsequently developed metastasis within a few months. ALK rearrangement remains the primary driver gene and therapeutic target for this type of tumor. From the perspective of predicting tumor biology, genetic variations at the DNA level, in addition to clinicopathological parameters, are equally significant and may provide a critical foundation for prognosis.

Systematic assessment of tumor necrosis at baseline in cervical cancer - An independent factor associated with poor outcome

Cervical cancer (CC) is a leading challenge in oncology worldwide, with high prevalence and mortality rates in young adults, most prominent in low to middle-income countries with marginal screening facilities. From the prospectively collected BioRAIDS (NCT02428842) cohort of primary squamous CC conducted in 7 European countries, a central pathology review was carried out on 294 patients' tumors. The focus was on identification of tumor-stromal characteristics such as CD8

Gonadoblastoma: origin and outcome

Classical gonadoblastoma occurs almost entirely in the dysgenetic gonads of an individual who has a disorder of sex development; however, a small number of cases arise in individuals with a normal peripheral karyotype and no evidence of a disorder of sex development. Those gonadoblastomas that occur in an individual who has a Y chromosome or part thereof express testis specific protein Y-encoded 1 (TSPY1). If a gonad in those individuals contains germ cells with delayed maturation and also harbors the TSPY1 gene, the cells can undergo transformation to classical gonadoblastoma. The latter consists of rounded islands composed of germ cells, sex cord elements, and hyaline basement membrane material surrounded by a variably cellular stroma that sometimes contains steroid cells. Classical gonadoblastoma can be interpreted as a noninvasive or an in situ neoplasm that is the precursor of germinoma in some individuals and, indirectly, of other more aggressive germ cell neoplasms. The "dissecting" variant is derived from classical gonadoblastoma and is characterized by unusual growth patterns. Undifferentiated gonadal tissue is the precursor of gonadoblastoma; however, if all germ cells in an individual with undifferentiated gonadal tissue involute, the result is a secondary streak gonad. Undifferentiated gonadal tissue is a non-neoplastic condition resembling a streak gonad but additionally contains germ cells with delayed maturation that express octamer-binding transcription factor 4; however, other germ cells, show normal maturation and express TSPY1.

Estrogen receptor expression in human tumors: A tissue microarray study evaluating more than 18,000 tumors from 149 different entities

NCOA1/2/3 rearrangements in uterine tumor resembling ovarian sex cord tumor: A clinicopathological and molecular study of 18 cases

Recurrent NCOA1/2/3 gene fusions emerged in uterine tumor resembling ovarian sex cord tumor (UTROSCT). More cases are required to consolidate these molecular alterations. In this study, the clinicopathological features and immunostaining profiles were reviewed in 18 UTROSCT. Fluorescence in situ hybridization for dual color break-apart probes of NCOA1, NCOA2, NCOA3, BCOR, YWHAE, PHF1 and JAZF1 were performed on 16 tumors. Eight cases were subjected to targeted next-generation sequencing to detect genomic alterations. We found that the tumors predominantly showed various sex-cord patterns without a recognizable endometrial stromal component. They exhibited a diverse immunohistochemical profile, frequently co-expressing sex cord (calretinin, inhibin, WT1, SF-1, and FOXL2), smooth muscle (SMA, desmin and caldesmon), epithelial (CK) and other markers (CD10 and IFITM1). Fourteen of 16 tumors (87.5%) showed NCOA1-3 gene rearranges, but none had BCOR, YWHAE, PHF1 and JAZF1 fusions. Five tumors contained 6 non-recurrent pathogenic (likely) mutations and one had gains in c-MYC. Our study supports frequent NCOA1-3 rearrangements in UTROSCT. Rare, non-recurrent mutations suggest that these gene rearrangements be potential drivers in tumorigenesis. Detection of gene rearrangements can contribute to the correct interpretation of UTROSCT. However, large comparative studies with molecular tests are required to confirm these findings.

An update on diagnostic tissue-based biomarkers in testicular tumors

Testicular cancer is rare overall but comprises the most common solid malignancy diagnosed in young men aged ∼20-40 years. Most testicular neoplasms generally fall into 2 broad categories: germ cell tumors (GCTs; ∼95%) and sex cord-stromal tumors (SCSTs ∼5%). Given the relative rarity of these tumors, diagnostic biomarkers are highly relevant for their diagnosis. Over the past several decades, diagnostic biomarkers have improved dramatically through targeted immunohistochemical and molecular characterization. Despite these recent advances, most markers are not perfectly sensitive or entirely specific. Therefore, they need to be used in combination and interpreted in context. In this review, we summarize tissue-based biomarkers relevant to the pathologist, with a focus on practical diagnostic issues that relate to testicular GCT and SCST.

Ovarian tumors: a survey of selected advances of note during the life of this journal

The author reviews highlights of advances in knowledge concerning ovarian tumor pathology since the time of an essay in the first issue of this Journal written by Dr Robert E. Scully, who, both before and for several decades after the Journal was instituted, made many original contributions to the field and was the major architect of the 1973 World Health Organization classification of ovarian tumors which was much more clear and logical than prior ones. The current review considers the neoplasms in essentially the same order as was done in the first issue of this journal and presents a personal look at the highlights of new information concerning various well-known categories, surface epithelial, germ cell, sex cord-stromal, metastatic neoplasms and briefly, benign so-called tumor-like lesions. Some of the most notable developments are as follows: (1) an orderly approach to the classification of implants of serous borderline tumors into noninvasive and invasive categories; (2) recognition of distinctive micropapillary patterns seen in some borderline tumors and low-grade carcinomas; (3) a remarkable propensity for some endometrioid carcinomas to mimic sex cord- stromal tumors; (4) appreciation of the differences between primary mucinous tumors of intestinal and müllerian types; (5) the importance of distinguishing within primary mucinous carcinomas between expansile and destructive stromal invasion; (6) emphasis on the diagnosis of immature teratoma being based on the presence of primitive-embryonic-appearing tissues; (7) appreciation of variant morphology of cases of struma ovarii which may lead to significant diagnostic problems; (8) subdivision of granulosa cell tumors into adult and juvenile types because of the differing features of the two groups including in the second category the propensity for more malignant neoplasms to be mimicked; (9) recognition of a distinctive form of Sertoli-Leydig cell tumor, the retiform variant, with a propensity to occur in the young; (10) appreciation of a unique highly malignant neoplasm that typically afflicts the young and may be associated with hypercalcemia, so-called small cell carcinoma of hypercalcemic type; (11) greater awareness than was hitherto the case of the propensity for metastatic intestinal adenocarcinoma to mimic primary endometrioid carcinoma and similarly for metastatic mucinous carcinomas to simulate primary mucinous cystic tumors; (12) recognition of the distinctive features of low-grade appendiceal mucinous neoplasms that spread to the ovary and are typically associated with pseudomyxoma peritonei; and (13) appreciation that the histologic spectrum seen in cases of Krukenberg tumor is broader than often previously thought.

Molecular subtype diagnosis of endometrial carcinoma: comparison of the next-generation sequencing panel and Proactive Molecular Risk Classifier for Endometrial Cancer classifier

The Cancer Genome Atlas-based molecular classification of endometrial carcinoma (EC) has the potential to better identify those patients whose disease is likely to behave differently than predicted when using traditional risk stratification; however, the optimal approach to molecular subtype assignment in routine practice remains undetermined. The aim of this study was to compare the results of two different widely available approaches to diagnosis the EC molecular subtype. EC specimens from 60 patients were molecularly subclassified using two different methods, by using the FoundationOne CDx next-generation sequencing (NGS) panel and using the Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE) classifier and performing immunostaining for mismatch repair proteins and p53. POLE mutation status was derived from FoundationOne results in both settings. Molecular classification based on ProMisE was successful for all 60 tumors. Microsatellite instability status could be determined based on the NGS panel results in 53 of 60 tumors, so ProMisE and NGS molecular subtype assignment could be directly compared for these 53 tumors. Molecular subtype diagnosis based on NGS and ProMisE was in agreement for 52 of 53 tumors. One tumor was microsatellite stable but showed loss of MLH1 and PMS2 expression. Molecular subtype diagnosis of EC based on the NGS panel of formalin-fixed paraffin-embedded ECs and based primarily on immunostaining (ProMisE) yields identical results in 98.1% (52/53, kappa = 0.97) of cases. Although results obtained using these two approaches are comparable, each has advantages and disadvantages that will influence the choice of the method to be used in clinical practice.

Reclassification of atypical immature metaplasia of the uterine cervix by combination of nuclear features on hematoxylin and eosin–stained sections without auxiliary immunohistochemistry

Reclassification of endocervical atypical immature metaplasia (AIM) into reactive changes and neoplastic lesion is often challenging. We aimed to accurately reclassify AIM on hematoxylin and eosin (HE)-stained sections without auxiliary immunohistochemistry (IHC). A total of 133 AIM diagnosed by punch biopsy were reclassified by IHC for p16 and Ki-67 into high-grade squamous intraepithelial lesion (HSIL) or negative for intraepithelial lesion or malignancy or low-grade squamous intraepithelial lesion (NILM/LSIL) as a reference. Nuclear features significantly associated with HSIL on HE-stained sections were extracted by multivariate logistic regression analysis. Propensity score (PS) of HSIL was calculated in each case and cut-off was determined by receiver operation characteristic (ROC) curve analysis. As a result, AIM was reclassified into 104 NILM/LSIL and 29 HSIL by IHC. Compared with reference diagnosis, accuracy of pathologists' subjective diagnosis was 54.9% (kappa coefficient, 0.208). Three nuclear features on HE-stained sections, ie, nuclear enlargement with anisokaryosis, nuclear hyperchromasia, and mitosis, were significantly associated with HSIL. The ROC curve analyses revealed that PS and number of nuclear features were significant predictors of HSIL. Diagnostic accuracy of PS-based diagnosis was 76.7% (kappa, 0.447). When AIM with 2 or more of the 3 nuclear features was diagnosed with HSIL, diagnostic accuracy was 77.4% (kappa, 0.448). Nuclear feature-based diagnosis significantly improved diagnostic accuracy on HE-stained sections compared with subjective diagnosis and may be useful when IHC is not available. However, a considerable proportion of AIM would still remain misdiagnosed and IHC for p16 and Ki-67 should be mandatory for accurate reclassification.

Endometrial carcinomas – Challenges and updates on selected topics

Endometrial carcinoma comprises a heterogeneous group of tumors with distinct histologic, immunophenotypic, and molecular profiles that have important diagnostic and clinical implications. This review focuses on selected subtypes of endometrial carcinomas with the most update. Endometrial serous carcinoma, though representing ∼10 % of endometrial cancers, accounts for a disproportionate number of endometrial cancer deaths; its early forms - serous endometrial intraepithelial carcinoma and superficial serous carcinoma, collectively termed minimal uterine serous carcinoma (MUSC) - predominantly arise in an endometrial polyp and demonstrate a paradoxically high rate of extrauterine spread despite minimal tumor volume, mandating comprehensive staging. Corded and hyalinized endometrioid carcinoma (CHEC) and pilomatrix-like high-grade endometrial carcinoma (PiMHEC) are CTNNB1/β-catenin-driven variants of endometrioid carcinoma with biphasic or basaloid morphology that may mimic carcinosarcoma, serous, or squamous carcinoma and show variable, sometimes aggressive behavior. Mesonephric-like adenocarcinoma (MLA) is an ER/PR-negative, KRAS-mutated carcinoma with mesonephric-type morphology, frequent deep myometrial and lymphovascular invasion, and a predilection for pulmonary metastasis. Primary endometrial squamous cell carcinoma (PESCC) and endometrial gastric (gastrointestinal)-type mucinous carcinoma (EmGA) are exceptionally rare entities that require stringent exclusion of cervical or metastatic primaries and are typically associated with p53-abnormal and/or gastrointestinal-type molecular signatures and poor outcomes. Across these variants, integration of morphology with immunohistochemistry and molecular testing (including p53, MMR status, POLE) is essential for accurate classification and risk stratification. HER2 overexpression and/or amplification occurs in 25-30 % endometrial serous carcinoma and HER2 testing has become a standard biomarker for selecting patients with recurrent or advanced disease for trastuzumab, and more recently trastuzumab-deruxtecan therapy.

Adaptive immune response and PD-1/ PD-L1 status in chemotherapy treated high grade serous carcinoma is dependent on chemotherapy response score

Platinum-based chemotherapy and debulking surgery is the standard of care for patients with advanced tubo-ovarian high-grade serous carcinoma (HGSC). The chemotherapy response scoring (CRS) system is a histopathologic scoring system developed to measure response to neoadjuvant chemotherapy with prognostic implications. Omental samples with high CRS have greater inflammatory cell infiltrates, but the immunophenotype of infiltrating immune cells and PD-L1 expression of the residual tumor has not been well-defined. Twenty cases of patients with FIGO stage IIIA to IIIC HGSC undergoing interval debulking after receiving 3-4 rounds of chemotherapy were selected. 6/20 cases of omental samples were graded as CRS 1, 7/20 were graded CRS 2, and 7/20 were graded CRS 3. The following immunohistochemical stains were performed: CD8, CD4, Foxp3, PD1, and PD-L1. The total number of tumor-infiltrating lymphocytes was recorded, and each case was given a PD-L1 combined positive score (CPS) and tumor proportion score (TPS). There was a significantly greater number of CD8 Tubo-ovarian high-grade serous carcinoma with greater response to neoadjuvant treatment have significantly greater T cell infiltrate and greater PD-L1 combined positive score, highlighting a potential role of the CRS as a predictive biomarker for immune checkpoint blockade therapy.

Ovarian GLI1 fusion tumors mimicking sex cord-stromal Tumors: Clinicopathological and molecular characterization of a five-case series

Ovarian GLI1 fusion tumors are rare mesenchymal neoplasms that closely mimic sex cord-stromal tumors (SCSTs) in both morphology and immunophenotype, frequently leading to misdiagnosis. In this study, we identified five such cases through re-evaluation of SCST-like ovarian tumors. Histologically, three distinct patterns were observed: the spindle pattern, the stellate/microcystic pattern and the epithelioid pattern. Immunophenotypically, all cases showed overlapping features with SCSTs, including CD10 expression and variable positivity for sex cord-stromal markers such as FOXL2, SF1, and Calretinin. Molecular analysis revealed recurrent ACTB::GLI1 fusions in four cases and a novel FUBP1::GLI1 fusion in one. Meta-analysis integrating our cases with ten previously reported ovarian GLI1 fusion tumors showed that these tumors predominantly occur in middle-aged women and present as significantly larger masses than their soft tissue and solid organ counterparts (P < 0.05). Notably, the relapse and metastasis rates of ovarian GLI1 fusion tumors were similar to adult granulosa cell tumors (AGCTs). In contrast, their recurrence rate was significantly higher than that of microcystic stromal tumors (MCSTs) (P < 0.05), indicating a more aggressive clinical course. Transcriptomic analysis revealed no significant correlation between ovarian GLI1 fusion tumors and sclerosing stromal tumors. These findings underscore the necessity of molecular testing for GLI1 rearrangements in SCST-like ovarian tumors to ensure accurate diagnosis and appropriate clinical management.

Deep learning-based analysis of gross features for ovarian epithelial tumors classification: A tool to assist pathologists for frozen section sampling

Computational pathology has primarily focused on analyzing tissue slides, neglecting the valuable information contained in gross images. To bridge this gap, we proposed a novel approach leveraging the Swin Transformer architecture to develop a Swin-Transformer based Gross Features Detective Network (SGFD-network), which assist pathologists for locating diseased area in ovarian epithelial tumors based on their gross features. Our model was trained on 4129 gross images and achieved high accuracy rates of 88.9 %, 86.4 %, and 93.0 % for benign, borderline, and carcinoma group, respectively, demonstrating strong agreement with pathologist evaluations. Notably, we trained a new classifier to distinguish between borderline tumors and those with microinvasion or microinvasive carcinoma, addressing a significant challenge in frozen section sampling. Our study was the first to propose a solution to this challenge, showcasing high accuracy rates of 85.0 % and 92.2 % for each group, respectively. To further elucidate the decision-making process, we employed Class Activation Mapping-grad to identify high-contribution zones and applied k-means clustering to summarize these features. The resulting clustered features can effectively complement existing knowledge of gross examination, improving the distinction between borderline tumors and those with microinvasion or microinvasive carcinoma. Our model identifies high-risk areas for microinvasion or microinvasive carcinoma, enabling pathologists to target sampling more effectively during frozen sections. Furthermore, SGFD-network requires only a single 4090 graphics card and completes a single interpretation task in 3 min. This study demonstrates the potential of deep learning-based analysis of gross features to aid in ovarian epithelial tumors sampling, especially in frozen section.

Characterization of gastric/gastrointestinal-like immunophenotypes in endometrial endometrioid adenocarcinomas, including endometrioid adenocarcinomas with mucinous differentiation

Endometrial mucinous carcinoma of the gastric [gastrointestinal] type (MCG) is a rare, possibly aggressive subtype of endometrial cancer that should be distinguished from its potential mimics, including endometrioid carcinoma (EEC). Herein, we assess the frequency of gastric and gastrointestinal immunophenotypes in EEC without any discernible gastric/gastrointestinal-type morphology. Immunohistochemical analyses for KRT(CK)7, KRT20, CDX2, ER, SATB2, MUC6, PAX8, and HIK1083 were performed on 81 EEC, inclusive of consecutively archived low grade [with (n = 22) and without (n = 47) mucinous differentiation] and high grade (n = 12) cases. None displayed gastric-type morphology or goblet cells. Expression levels were semi-quantified as H-scores (combining intensity and extent of staining) on a standardized 0-300 scale. Among the gastric/gastrointestinal-type markers, 56%, 62%, 23%, 25%, and 0% of cases expressed MUC6, CDX2, KRT20, SATB2, and HIK1083 respectively. The expression levels for positive cases were generally limited, with average H-scores being 49.5 [range 1-250] for MUC6, 33.7 [1-285] for CDX2, 24.0 [1-270] for CK20, and 30.5 [2-220] for SATB2. Ten (12.35%) cases showed high expression (H ≥ 200) of at least 1 gastric/gastrointestinal-type marker, including 1, 2, 2 and 6 cases that were high positive for KRT20, SATB2, CDX2 and MUC6 respectively. Immunoreactive foci were generally indistinguishable from background at the morphologic level. There was no statistically significant correlation between the expression of any of the gastric/gastrointestinal-type markers and ER, KRT7 or PAX8 expression. In summary, gastric/gastrointestinal-type proteins are not uncommonly expressed at low levels in EEC. As such, positivity for these markers cannot be the sole basis for distinguishing EEC from MCG.

DICER1-sarcomas of GYN tract: Expanding on an emerging entity

Tumors with pathogenic DICER1 mutation are rare and encompass sporadic or hereditary benign, intermediate and malignant tumors. DICER1-associated sarcomas are heterogeneous; however, the prototypical ones in the GYN-tract include embryonal rhabdomyosarcoma, adenosarcoma and moderately to poorly differentiated Sertoli-Leydig tumor. In this report, we present three unique uterine sarcomas with DICER1 mutation and remarkable diffuse round/spindle cell morphology. The tumors occurred in cervix (n = 1), and uterine corpus (n = 2). The patient ages were 30, 37 and 59 years with tumor size of 8.8, 10 and 8.6 cm, respectively. Morphologically all three tumors were characterized by distinct spindle/round cell morphology and various amounts of neuroectodermal differentiation (yolk sac-like tubules, blastomatous areas and rosette formation). Other morphologic features of DICER1-sarcoma reported in the literature including cambium layer, focal or diffuse anaplasia, solid and cystic architecture, and chondroid/osteoid areas were absent. All three sarcomas were positive for SALL4 and had variable neuroendocrine marker expression. Whole genome methylation analysis was performed on one of the uterine sarcomas, which clustered the tumor with embryonal tumor with multilayered rosettes. Follow up information was available on all three cases. Two patients were alive with no evidence of disease 13 and 14 months post operation, while one patient had imaging evidence of local recurrence 4 months post operation. In summary, we describe three unique DICER1-sarcomas and expand the phenotypic spectrum of this emerging entity, particularly with GYN-tract origin.

Uterine adenosarcoma: Clinical significance of histological classification and SNP array analysis

Mullerian adenosarcoma is a rare malignant biphasic tumor. The mesenchymal component may be low or high grade, with or without sarcomatous overgrowth (SO). Little is known about the molecular heterogeneity of these tumors. In this study, we aim to reclassify a large retrospective monocentric cohort of uterine adenosarcomas according to tumor grade and SO, to evaluate the clinical significance of pathological classification and to correlate with copy-number variations inferred from single nucleotide polymorphism array. Of the 67 uterine adenosarcomas, 18 (26.9%) were low grade without SO, 7 (10.4%) low grade with SO, 8 (11.9%) high grade without SO and 34 (50.7%) high grade with SO. SO, necrosis and RMS were more frequent in high grade than low grade adenosarcomas (p < 0.001). Low-rank test showed that recurrence-free survival was significantly shortened in high grade than low grade adenosarcomas (p = 0.035) and SO was associated with shortened overall and recurrence-free survival (p = 0.038 and p = 0.009, respectively). High-grade tumors displayed complex genomic profiles with multiple segmental losses including TP53, ATM and PTEN genes. The median genomic index was significantly higher in high grade than low grade tumors (27 [3-60] vs 5,3 [0-16], p < 0.0001) and was significantly higher in presence of SO in low grade tumors (12,8 [10-16] vs 2,6 [0-10], p = 0.0006). We propose to report sarcomatous overgrowth with the tumor grade for prognostication in adenosarcoma and representative sampling is crucial for evaluation of these histological criteria.

Benign female genital tract smooth muscle tumors with adipocytic differentiation: A morphologic, immunohistochemical and MDM2 fluorescence in situ hybridization study of 44 conventional lipoleiomyomas and lipoleiomyoma variants

Leiomyomas with adipocytic differentiation typically occur in the uterus although they may arise at several sites in the female genital tract. While these are most commonly spindled leiomyomas with a component of adipocytic tissue ("conventional lipoleiomyomas"), there is a relatively ill-defined assortment of leiomyoma variants with adipocytic differentiation. We performed a morphologic, immunohistochemical and MDM2 gene amplification analysis of a large series of gynecologic leiomyomas with adipocytic differentiation to better define the clinicopathologic spectrum. Forty four tumors from 44 patients were identified and classified as conventional lipoleiomyoma (n = 21), adipocyte-rich lipoleiomyoma (defined as tumor volume >80 % adipocytes, n = 9); cellular lipoleiomyoma (n = 9); hydropic lipoleiomyoma (n = 3); and lipoleiomyoma with bizarre nuclei (n = 2). Patient age ranged from 32 to 83 years (mean 63; median 63). Primary location included uterine corpus (35), uterine cervix (3), uterine corpus/cervix (1), broad ligament (2), parametrium (2), and round ligament (1). Tumor size was 0.6-30 cm (mean 8; median 6). None of the 34 patients with follow up developed further disease (range 1-311 months; mean 65; median 41). Immunohistochemical expression of ER, PR, HMB45, Melan A, Cathepsin K and WT-1 in lipoleiomyomas and variants was similar to patterns in non-adipocytic gynecologic leiomyomas. MDM2 amplification fluorescence in situ hybridization performed on 14 tumors was negative in all. Our findings suggest female genital tract conventional lipoleiomyomas and lipoleiomyoma variants largely parallel their non-adipocytic counterparts in morphology and immunophenotype, and may be categorized using non-adipocytic leiomyoma histologic criteria.

Brenner tumor associated with rete ovarii: a histologic and immunohistochemical analysis of six cases exploring the relationship between these entities

The association of Brenner tumor (BT) with rete ovarii (RO) has been rarely alluded to in the literature. Both entities have debatable histogenesis. In this study of six cases of BT associated with RO, we describe the morphologic features and performed immunohistochemical staining for markers of Mullerian, Wolffian, mesothelial, and sex cord stromal derivation to explore the relationship between these entities. Histologically, all BTs were benign, microscopic, and incidental. RO was prominent and hyperplastic with gradual or abrupt transition to BT. In addition, focal areas of rete entrapped between BT nests were seen. All BTs were positive for GATA-3 and negative for PAX-8. Conversely, the RO in all cases was negative for GATA-3 and positive for PAX-8. WT-1 was positive in both entities. Sex cord stromal and mesothelial markers (other than WT-1) were negative in BT and RO. Although morphologically, BTs seem to arise from RO in these cases, they have a distinct immunophenotype. It is possible that at least some BTs arise from metaplastic changes in RO epithelium.

A diagnostic approach to paratesticular lesions with tubulopapillary architecture: a series of 16 serous borderline tumors/low-grade serous carcinoma and 14 well-differentiated papillary mesothelial tumors and mesothelioma

As there is limited literature on paratesticular tumors of müllerian and mesothelial origin, we reviewed archived cases of serous borderline tumors (n = 15), low-grade serous carcinoma (n = 1), well-differentiated papillary mesothelial tumors (WDPMTs; n = 2), and mesothelioma (n = 12), for relevant clinicopathologic features. Molecular profiling data from the American Association for Cancer Research (AACR) GENIE registry was accessed for 8 additional patients with testicular mesothelioma. For tumors of mesothelial origin, the median age at surgical excision was 62 years, the median size was 4.5 cm, and they consistently exhibited positivity for mesothelial markers (CK5/6, calretinin, WT1, and D2-40). Recurrent alterations of the NF2 gene were identified in 3 of 8 patients (38%), and alterations of BAP1 and CDKN2A were relatively infrequent. While one patient with WDPMT had a recurrence, a second patient with WDPMT progressed to a biphasic mesothelioma 2 years after initial resection. For tumors of müllerian origin, the median age at surgical excision was 45 years, the median size was 2.5 cm, and these exhibited consistent positivity for ER, WT1, and PAX8. Although no recurrences were documented in patients with serous borderline tumors, a single patient with a low-grade serous carcinoma developed widely metastatic disease and died of disease-related complications. Our study emphasizes the need for close clinical follow-up in patients with WDPMT and highlights the prognostic significance of documenting invasive behavior in tumors of müllerian origin as they can have an aggressive clinical course. Finally, our results suggest that NF2 alterations may play an important role in the pathogenesis of testicular mesothelioma.

Assessment of Nectin4-expression in vulvar squamous cell carcinomas (VSCC): correlation with HPV-associated and HPV-independent molecular subtypes

The development of antibody-drug conjugates (ADC) for cancer treatment has achieved promising results in different solid tumors and targets. Enfortumab-Vedotin (EV), a humanised anti-Nectin4-IgG1 monoclonal antibody linked to the microtubule-disrupting agent monomethyl auristatin E (MMAE), is an FDA-approved Nectin4-directed ADC for the treatment of locally advanced or metastatic pre-treated urothelial cancer. Targeted therapy with EV requires the expression of Nectin4 within the tumor cells. The present study evaluates Nectin4 expression in vulvar squamous cell carcinomas (VSCC) and its correlation to different VSCC molecular subtypes. Immunohistochemical Nectin4-expression was evaluated semiquantitatively on diagnostic biopsies of VSCC using an immunoreactive score (IRS). There was a correlation between IRS and different molecular subtypes of VSCC. All 55 cases showed at least weak Nectin4 expression within the tumor cells with a median IRS of 6.0 (range 2-6) indicating high expression levels in most tumors. Moderate/high expression (IRS ≥4) was more frequent in HPV-associated tumors (p16 Most VSCC show high expression of Nectin4, including the HPV-independent VSCC containing a TP53-mutation (p16

Clinicopathologic and molecular characterization of primitive neuroectodermal tumors (PNET) in the female genital tract: a retrospective study of 8 cases

This study aimed to investigate the molecular alterations in primitive neuroectodermal tumors (PNET) of the female genital tract. We retrospectively analyzed the clinicopathologic and immunohistochemical features of 8 gynecologic PNET cases (3 cervical, 1 vaginal, and 4 ovarian). Fluorescence in situ hybridization and targeted next-generation sequencing (NGS) were performed to identify molecular alterations in these tumors. The cohort included 5 FIGO stage I, 1 stage III, and 2 stage IV tumors. Two patients with stage IV disease died at 8 and 12 months. The cervical/vaginal tumors consisted of small round blue cells arranged in sheets, with EWSR1 rearrangements and concurrent diffuse expression of membranous CD99 and nuclear FLI1. The ovarian tumors displayed diverse morphologic features resembling central nervous system (CNS) tumors, including embryonal tumor with multilayered rosettes (case 5), medulloblastoma (case 6), glioblastoma (case 7), and ependymoma (case 8). Three ovarian tumors were associated with teratomas. None of the ovarian tumors exhibited EWSR1 rearrangements or i(12p)/12p overrepresentation. NGS identified an EWSR1::exon11∼FLI1::exon6 fusion in one cervical PNET, with no additional molecular alterations. In contrast, three ovarian tumors lacked common genetic changes seen in CNS tumors but harbored several significant variants, including NTRK2 exon11 c.1019C > T (p.T340 M) (case 6), INPP4B exon23 c.2221G > A (p.V741 M) (case 7), and FANCG exon7 c.882_883insA (p.D295Rfs∗14) with MET 7q31 polysomy (case 8). Our findings confirm that cervical/vaginal and ovarian PNET represent two distinct tumor types. Ovarian PNET have different pathogenetic pathways from their CNS and testicular counterparts most likely.

Clinicopathological study of 34 cases of clear cell adenocarcinoma of the urinary tract and diagnostic value of SOX 17 in its differential diagnosis

Clear cell adenocarcinoma (CCA) of the urinary tract is a rare tumor with a female predominance. The morphological features and immunoprofile of urinary CCA, CCA of the gynecologic tract (Gyn CCA), and nephrogenic adenoma (NA) can show extensive overlap, and the differential diagnosis can be challenging especially in small biopsies. SOX17 is a newly identified sensitive and specific immunomarker for endometrial and ovarian carcinomas including Gyn CCA. However, its expression in urinary CCA and NA has not been studied. We studied clinical and pathological features of 34 cases of urinary CCA, the largest cohort in the literature to date. We analyzed the expression pattern of SOX17 in a cohort of 34 urinary CCA, 24 Gyn CCA, and 18 NA. Interestingly, 29 % (10/34) of urinary CCA showed high SOX17 expression, while all the NA cases (18/18) showed negative-low expression. In female, 51 % of urinary CCA cases (15/29) show negative-low expression of SOX17, whereas all Gyn CCA (24/24) showed high SOX17 positivity. Our study showed a unique expression pattern of SOX17 in urinary CCA and NA. These results suggest that SOX17 is a useful marker in distinguishing CCA from NA or urinary CCA from Gyn CCA. Moreover, our study suggests different pathogenic pathways for the histogenesis of urinary CCA.

Gradual telomere shortening in the tumorigenesis of pancreatic and hepatic mucinous cystic neoplasms

Therapeutic indications for antibody-drug conjugates estimated from HER2 and p53 expressions in endometrial carcinoma

While human epidermal growth factor receptor 2 (HER2) is upregulated in endometrial carcinoma-especially in the p53 aberrant type- conventional anti-HER2 therapy is not typically used for this cancer type. Recently, HER2-targeted antibody-drug conjugates have shown antitumor effects against HER2 low-expressing cancers. Therefore, we analyzed the clinicopathological characteristics of HER2-positive endometrial carcinomas including those with low expression, as well as the prognostic significance of p53 and HER2 co-expression. Immunohistochemistry for HER2 and p53 was performed in 530 patients with endometrial carcinoma; 124 cases (23%) were HER2-positive. Of the HER2-positive cases, >50% were 1+. A high prevalence of HER2 expression was observed in serous (64%), clear-cell (73%), and mixed (64%) carcinomas. Notably, 19% of endometrioid carcinomas were HER2-positive. HER2 positivity was significantly associated with age ≥60 years, high-grade histological subtype, deep myometrium invasion, stage III/IV, recurrence, and death. Univariate analysis showed that HER2-positive cases had reduced progression-free survival (PFS) (p = 0.007) and overall survival (OS) (p = 0.012). However, after adjusting for stage, HER2 positivity was not associated with survival. In the early stage, co-expression of HER2-positive and p53 aberrant types was associated with shorter PFS (p < 0.001) and OS (p < 0.001) compared with at least one negative result. Multivariate analysis of PFS showed HER2 and p53 co-expression (hazard ratio, 1.891; 95% confidence interval, 1.183-5.971, p = 0.008) as an independent prognostic factor. This study presents detailed clinicopathological characteristics and the prognostic impact of HER2-positivity in endometrial carcinomas. HER2-targeted antibody-drug conjugate therapy may be broadly applicable to endometrial carcinoma.

Minimal uterine serous carcinoma and endometrial polyp: a close clinicopathological relationship

Frequently involving an endometrial polyp, minimal uterine serous carcinoma (MUSC) represents the earliest recognizable forms of endometrial serous carcinoma. The aim of this study was to provide a comprehensive morphological and clinical outcome assessment of MUSC involving endometrial polyp. A total of 77 fully staged MUSCs involving endometrial polyp were identified, including 53 MUSCs confined to polyp and 24 nonpolyp confined tumors. Extrauterine disease was found in 17% (9/53) of polyp-confined MUSCs compared to 41.7% (10/24) of nonpolyp confined tumors (p = 0.02). Lymphovascular invasion was observed in 3.8% (2/53) of polyp-confined cases compared to 25% (6/24) of nonpolyp confined cases (p = 0.047). Lymph node metastasis was observed in 11.3% (6/53) of polyp-confined cases, compared to 29.2% (7/24) of nonpolyp confined cases (p = 0.058). Positive pelvic washing cytology was seen in 18.9% (10/53) of polyp-confined versus 37.5% (9/24) of nonpolyp confined tumors (p = 0.078). Overall, 58 of 77 (75.3%) patients had low tumor stage (57 stage I cases and 1 stage II case) and only two patients (3.5%) had a recurrence. In contrast, 19 of 77 (24.7%) patients had advanced stage (stage III or IV) disease and 17 (89.5%) patients had recurrence (p < 0.0001). Only one of 57 low-stage patient (1.7%) versus 11 of 19 high-stage patients (57.8%) died of the tumor (p < 0.0001). Five of 53 (9.4%) patients with polyp-confined MUSC and 7 of 24 (29.2%) patients with nonpolyp confined MUSC died of the disease (p = 0.03). In conclusion, while a small percentage of MUSCs exist without the involvement of an endometrial polyp, a close topographic relationship between MUSC and the endometrial polyp is confirmed in this largest series, supporting the theory that most if not all MUSCs arise in an EMP. Patients with MUSC without extrauterine spread have an excellent prognosis. Compared to patients with MUSC confined to an endometrial polyp, patients with MUSC extending to the background endometrium have a significantly higher risk for high-stage disease at presentation.

Expanding the spectrum of paratesticular mullerian-origin tumors: Adenocarcinoma with mixed serous and endometrioid features and clear cell carcinoma

Analysis of discordance between mismatch repair and microsatellite instability testing in endometrial cancer

Accurate molecular classification of endometrial carcinoma (EC) is critical for guiding therapy, particularly concerning mismatch repair-deficient (MMRd). However, the consistency of MMRd detection across different diagnostic modalities and the molecular basis of discordant results remain insufficiently characterized. In this retrospective study, 220 EC patients treated at Zhejiang Cancer Hospital from January 2021 to March 2024 underwent histopathological review, immunohistochemistry (IHC), and targeted next-generation sequencing (NGS) with a 196-gene panel. Discordant cases were further assessed by polymerase chain reaction (PCR)-based microsatellite instability (MSI) testing, MLH1 promoter methylation analysis, and extended mutational profiling. The median age of the study cohort was 57.0 years. IHC revealed deficient mismatch repair (dMMR) in 65 cases (29.6 %), while NGS detected high MSI (MSI-H) in 44 cases (20.0 %), yielding an overall 90.5 % concordance. All 21 discordant cases (9.5 %) displayed dMMR by IHC but microsatellite stable (MSS) by NGS. PCR reclassified five cases as MSI-H, whose MSIsensor scores were significantly higher than proficient MMR (pMMR)/MSS tumors (p = 0.01) but lower than dMMR/MSI-H tumors (p = 0.0007). Of the remaining 16 unresolved cases, 43.8 % exhibited isolated MSH6 loss, likely due to the functional compensation of MSH3, while 56.2 % showed MLH1 loss, predominantly due to MLH1 promoter methylation (77.8 %). In conclusion, discordance between IHC- and NGS-based MMR/MSI detection is primarily attributable to MSH6 loss with MSH3 compensation and MLH1 promoter methylation. Recognizing these mechanisms is essential for accurate molecular subtyping and clinical decision-making in EC.

High-grade endometrioid carcinomas with pilomatrix-like features lacking CTNNB1 Mutations: Clinicopathologic characteristics and novel molecular events

Pilomatrix-like high-grade endometrioid carcinoma (PiMHEC) represents a recently described, aggressive variant of endometrial carcinoma. Prior reports have linked PiMHEC with CTNNB1 exon 3 mutations and abnormal nuclear β-catenin expression. We aimed to expand the understanding a potential subclassification of PiMHEC by analyzing three new cases that lack CTNNB1 mutations and β-catenin nuclear accumulation. Three cases of high-grade endometrioid carcinomas with pilomatrix-like features were identified and their clinical presentations and pathologic features reviewed. Immunohistochemistry (IHC) and targeted next-generation sequencing (NGS) were performed. All tumors demonstrated two components: a high-grade basaloid component with solid sheets of atypical basaloid cells, geographic necrosis, and focal "ghost" cells, and an associated low-grade FIGO grade 1 endometrioid carcinoma component. Notably, none of the three cases showed nuclear β-catenin expression by IHC, and all lacked CTNNB1 exon 3 mutations. Despite this, the tumors fulfilled the morphologic criteria for PiMHEC described in prior studies and displayed aggressive clinical behavior. All the patients presented with advanced-stage disease (stages IIC-IVB), and two patients had a recurrence within 12 months. NGS revealed no CTNNB1 mutations in any case, but identified alternative likely oncogenic alterations: one tumor harbored an FGFR4 p. T259A mutation, two tumors had pathogenic TSC2 mutations, one had a KRAS p.G12D mutation, and two showed MYC amplification, among other genetic changes. High-grade endometrioid carcinomas with pilomatrix-like features lacking CTNNB1 mutations may represent a potential subclassification of PiMHEC, which exhibit aggressive behavior. CTNNB1-wildtype cases appear to rely on alternative oncogenic drivers, indicating that CTNNB1 mutation maybe not an absolute requirement for the PiMHEC phenotype.

PD-L1 expression and immune infiltration across molecular subtypes of endometrial cancer: An integrative-analysis of molecular classification and immune subtypes

The immune subtypes of the tumor microenvironment in endometrial cancer (EC), associated with different molecular classifications, warrant further investigation to guide EC immunotherapy strategies. This study focused on programmed death-ligand 1 (PD-L1) expression (Clone SP263) and immune cell (IC) markers (CD3, CD8, CD68, CD20, CD21) in 110 EC cases. In this cohort, the molecular subtype distribution was: POLE mutation (POLEmut) 7.3% (8/110), mismatch repair-deficient (MMRd) 21.8% (24/110), p53 abnormal (p53abn) 14.5% (16/110), and non-specific molecular profile (NSMP) 56.4% (62/110). NSMP subtypes exhibited the lowest PD-L1+ cell densities and scores. POLEmut and MMRd subtypes showed higher IC densities, while p53abn and NSMP subtypes had lower IC densities and fewer tertiary lymphoid structures (TLS). Integrative analysis of immune subtypes with PD-L1 and CD8

ARID1A, BRG1, and INI1 deficiency in undifferentiated and dedifferentiated endometrial carcinoma: a clinicopathologic, immunohistochemical, and next-generation sequencing analysis of a case series from a single institution

Undifferentiated/dedifferentiated endometrial carcinomas (UDEC and DDEC) are rare, aggressive uterine neoplasms, with no specific line of differentiation. A significant proportion of these cases feature mutations of SWI/SNF chromatin remodeling complex members, including ARID1A, SMARCA4, and SMARCB1 genes. To study these entities more comprehensively, we identified 10 UDECs and 10 DDECs from our pathology archives, obtained clinicopathologic findings and follow-up data, and performed immunohistochemical studies for ARID1A, BRG1 (SMARCA4), and INI1 (SMARCB1) proteins. In addition, we successfully conducted targeted next-generation sequencing for 23 samples, including 7 UDECs, and 7 undifferentiated and 9 well/moderately-differentiated components of DDECs. Cases consisted of 18 hysterectomies and 2 curettage/biopsy specimens. Patient age ranged from 47 to 77 years (median, 59 years), with a median tumor size of 8.0 cm (range, 2.5-13.0 cm). All cases demonstrated lymphovascular invasion and the majority (13/20) were FIGO stage III-IV. By immunohistochemistry, ARID1A loss was observed in 15 cases, BRG1 loss in 4, and all cases had intact INI1 expression. A trend for enrichment of the undifferentiated component of DDECs for ARID1A loss was seen, although not statistically significant. Sequencing revealed frequent pathogenic mutations in PTEN, PIK3CA, ARID1A, CTNNB1, and RNF43, a recurrent MAX pathogenic mutation, and MYC and 12p copy number gains. In DDECs, the undifferentiated component featured a higher tumor mutational burden compared to the well/moderately-differentiated component; however, the mutational landscape largely overlapped. Overall, our study provides deep insights into the mutational landscape of UDEC/DDEC, SWI/SNF chromatin remodeling complex member status, and their potential relationships with tumor features.

Critical aspects of microsatellite instability testing in endometrial cancer: a comparison study

The identification of mismatch repair deficient (dMMR) and microsatellite unstable (MSI) endometrial cancers (ECs) is important in screening, diagnosis, and therapeutic stratification of patients. We compared the diagnostic performance of 4 MSI molecular tests based on fragment length assay in capillary electrophoresis (OncoMate™ MSI assay, Promega) and in microcapillary electrophoresis (TapeStation 4200, Agilent); with high-resolution melting (HRM) analysis approaches (Idylla™ MSI Test, Biocartis; EasyPGX® ready MSI, Diatech Pharmacogenetics) on a series of 56 ECs, which was well characterized for MMR status with immunohistochemical approach (IHC, nonmolecular reference test). The concordance of fluorescence capillary electrophoresis with IHC (AUC 0.98) was higher respect to the other molecular methodologies. Otherwise, HRM approaches and microcapillary electrophoresis platform failed to detect MSI-ECs showing minimal microsatellite shifts. In conclusion, in colorectal site, several technologies are eligible for MSI test, whereas in ECs, MSI test should be based on fluorescent capillary electrophoresis as it identifies a higher proportion of cases that could be misdiagnosed with other strategies.

Discrepancies in pathological diagnosis of endometrial stromal sarcoma: a multi-institutional retrospective study from the Japanese clinical oncology group

Endometrial stromal sarcoma (ESS) is a rare uterine malignancy that requires accurate pathological diagnosis for proper treatment. This study aimed to clarify the discrepancies in the pathological diagnosis of ESS and obtain practical clues to improve diagnostic accuracy. Between 2002 and 2015, 148 patients with low-grade ESS (LGESS), high-grade ESS (HGESS), undifferentiated endometrial sarcoma (UES), or undifferentiated uterine sarcoma (UUS) diagnosed at 31 institutions were included. We performed immunohistochemistry, real-time polymerase chain reaction for JAZF1-SUZ12 and YWHAE-NUTM2A/B, and break-apart fluorescent in situ hybridization for JAZF1, PHF1, and YWHAE. Central pathology review (CPR) was performed by six pathologists. After CPR, LGESS, HGESS, UES/UUS, and other diagnoses were confirmed in 72, 25, 16, and 31 cases, respectively. Diagnostic discrepancies were observed in 19.6% (18/92) of LGESS and 34% (18/53) of HGESS or UUS/UES. Adenosarcomas, endometrial carcinomas, carcinosarcomas, and leiomyosarcomas were common diagnostic pitfalls. JAZF1-SUZ12 transcript, PHF1 split signal, and YWHAE-NUTM2A/B transcript were mutually exclusively detected in 23 LGESS, 3 LGESS, and 1 LGESS plus 3 HGESS, respectively. JAZF1-SUZ12 and YWHAE-NUTM2A/B transcripts were detected only in cases with CPR diagnosis of LGESS or HGESS. The CPR diagnosis of LGESS, HGESS, and UUS was a significant prognosticator, and patients with LGESS depicted a favorable prognosis, while those with UUS showed the worst prognosis. Pathological diagnosis of ESS is often challenging and certain tumors should be carefully considered. The accurate pathological diagnosis with the aid of molecular testing is essential for prognostic prediction and treatment selection.

The cutoff for estrogen and progesterone receptor expression in endometrial cancer revisited: a European Network for Individualized Treatment of Endometrial Cancer collaboration study

There is no consensus on the cutoff for positivity of estrogen receptor (ER) and progesterone receptor (PR) in endometrial cancer (EC). Therefore, we determined the cutoff value for ER and PR expression with the strongest prognostic impact on the outcome. Immunohistochemical expression of ER and PR was scored as a percentage of positive EC cell nuclei. Cutoff values were related to disease-specific survival (DSS) and disease-free survival (DFS) using sensitivity, specificity, and multivariable regression analysis. The results were validated in an independent cohort. The study cohort (n = 527) included 82% of grade 1-2 and 18% of grade 3 EC. Specificity for DSS and DFS was highest for the cutoff values of 1-30%. Sensitivity was highest for the cutoff values of 80-90%. ER and PR expression were independent markers for DSS at cutoff values of 10% and 80%. Consequently, three subgroups with distinct clinical outcomes were identified: 0-10% of ER/PR expression with, unfavorable outcome (5-year DSS = 75.9-83.3%); 20-80% of ER/PR expression with, intermediate outcome (5-year DSS = 93.0-93.9%); and 90-100% of ER/PR expression with, favorable outcome (5-year DSS = 97.8-100%). The association between ER/PR subgroups and outcomes was confirmed in the validation cohort (n = 265). We propose classification of ER and PR expression based on a high-risk (0-10%), intermediate-risk (20-80%), and low-risk (90-100%) group.

VHL-mutated papillary cystadenoma of the mesosalpinx with omental tumor deposits and immunophenotypic overlap with mesothelioma

LRP1B—a prognostic marker in tubo-ovarian high-grade serous carcinoma

Low-density lipoprotein (LDL) receptor-related protein 1B (LRP1B) is a member of the LDL receptor family and has often been discussed as a tumor suppressor gene, as its down-regulation is correlated with a poor prognosis in multiple carcinoma entities. Due to the high metastasis rate into the fatty peritoneal cavity and current research findings showing a dysregulation of lipid metabolism in tubo-ovarian high-grade serous carcinoma (HGSC), we questioned the prognostic impact of the LRP1B protein expression. We examined a well-characterized large cohort of 571 patients with primary HGSC and analyzed the LRP1B protein expression via immunohistochemical staining (both in tumor and stroma cells separately), performed precise bioimage analysis with QuPath, and calculated the prognostic impact using SPSS. Our results demonstrate that LRP1B functions as a significant prognostic marker for overall survival (OS) and progression-free survival (PFS) in HGSC on the protein level. High cytoplasmic expression of LRP1B in tumor, stroma, and combined tumor and stroma cells has a significantly positive association with a mean prolongation of the OS by 42 months (P = .005), 29 months (P = .005), and 25 months (P = .001), respectively. Additionally, the mean PFS was 18 months longer in tumor (P = .002), 19 months in stroma (P = .004), and 19 months in both cell types combined (P = .01). Our results remained significant in multivariate analysis. We envision LRP1B as a potential prognostic tool that could help us understand the functional role of lipid metabolism in advanced HGSC, especially regarding liposomal medications.

Precursors in the ovarian stroma: another pathway to explain the origin of ovarian serous neoplasms

Ovarian serous neoplasms are thought to arise from the fallopian tube or from the ovarian surface epithelium. The possibility of a third pathway-involving the mesenchymal-epithelial transition and mimicking the formation of the Müllerian duct-arose from observations gathered from our routine cases. The purpose of this study is to determine the association of precursors in the ovarian stroma with different types of ovarian serous neoplasms. Three hundred neoplasms, benign (25), borderline (63), and malignant ovarian serous neoplasms (40 low-grade serous carcinomas [LGSCas] and 172 high-grade serous carcinomas [HGSCas]), were reviewed. Clinicopathologic features analyzed included patient's age, tumor size, stage, histologic pattern, and possible precursors in the ovarian parenchyma (endosalpingiosis, inverted macropapillae, polyploid giant cancer cells, and simple cysts). All benign and borderline cases showed continuity with benign serous cysts or endosalpingiosis. In LGSCas, continuity with serous cysts was found in 29 (72%) of 40 cases, and inverted macropapillae were found in 12 (30%) of 40 cases. In untreated HGSCas, there was continuity with simple cysts in 42% of cases. In addition, these HGSCas contained polyploid giant cancer cells in 20% of cases. There were no different features in the ovaries in cases with or without serous tubal intraepithelial carcinoma. Our study shows that in a subset of cases, ovarian serous neoplasms and the Müllerian duct develop in similar fashion, originating from epithelial cells derived from the mesothelium, or occur de novo from structures derived from mesenchymal-epithelial transition.

TP53 variant allele frequency correlates with the chemotherapy response score in ovarian/fallopian tube/peritoneal high-grade serous carcinoma

Molecular findings in ovarian, fallopian tube, and peritoneal high-grade serous carcinoma (HGSCa) are emerging as potential prognostic indicators. The chemotherapy response score (CRS) has been proposed as a histologic-based prognostic factor in patients with HGSCa treated with neoadjuvant chemotherapy (NACT). No study details the relationship between the mutational landscape of HGSCa and the CRS. This study addresses this issue using next-generation sequencing (NGS). We retrospectively identified 25 HGSCas treated with NACT and pathology material available to calculate the CRS. All cases had NGS on the primary debulking specimen post-NACT. The three-tier Böhm CRS was applied to the omentum or adnexa and calculated as a combined score. Tumor mutation burden (TMB) and TP53 variant allele frequency (VAF) were calculated and used in correlative analysis. All cases had at least one mutation, most commonly TP53 (25 cases, 100%). Other mutations were BRCA2 (one case, 4%), ARID1A (two cases, 8%), and 1 (4%) of each of the following: ERBB2, NTRK3, STK11, NTRK2, TSC1, PIK3CA, NF1, NOTCH3, CDK2, SMAD4, and PMS2. TMB ranged from 2.58 to 7.75 (median 3.84). There was no statistically significant relationship between the TMB and omental CRS, R-squared = 0.011 (P = 0.62); adnexal CRS, R-squared = 0.005 (P = 0.74); or with the combined CRS, R-squared = 0.009 (P = 0.65). Statistically significant correlation was found between the TP53 VAF and the omental CRS (R-squared = 0.28, P = 0.007), adnexal CRS (R-squared = 0.26, P = 0.01), and the combined CRS (R-squared = 0.33, P = 0.0026). The TP53 VAF was adjusted for percent of tumor present on the slide resulting in an average per cell TP53 mutational load, resulting in similar results with a statistically significant correlation between the average per cell TP53 mutational load and the omental CRS (R-squared = 0.27, P = 0.02), adnexal CRS (R-squared = 0.16, P = 0.05), and the combined CRS (R-squared = 0.23, P = 0.02). In summary, NGS confirmed TP53 mutations in all cases of HGSCa. TMB showed no correlation with the CRS. TP53 VAF and average per cell TP53 mutational load showed significant correlation with the CRS, whether graded on the adnexa or omentum or as a combined score, indicating concordance between molecular and histological findings following NACT.

Morphologic and immunohistochemical study of HPV-related cervical adenosquamous carcinoma: Reappraisal of a poorly defined entity

Current WHO criteria require distinct glandular and squamous differentiation for diagnosis of adenosquamous carcinoma (AdSq). However, a subset of poorly differentiated cervical carcinoma exhibits ambiguous morphology with diffuse growth pattern. The current study explores whether these tumors belong to the adenosquamous subtype. After IRB approval, we retrieved 41 AdSq cases diagnosed at our institution between 2007 and 2024. H&E slides were reviewed. Immunohistochemical staining for p16, p40, p63, BerEP4, and Claudin-4 was performed. IHC was scored. Statistical analysis was performed with Python packages. Based on morphology only, out of the 41 AdSq cases, 11 fulfilled the WHO proposed criteria for classic AdSq (cAdSq). Twenty cases were classified as non-classic AdSq (nAdSq). All the rest also exhibited a solid growth pattern, but were reclassified as endocervical (3), endometrioid (6), and squamous carcinoma (1). Histologically, nAdSq lacked distinct spatially separate components of squamous or glandular differentiation. Instead, tumor cells exhibited ambiguous morphology with diffuse growth or, less frequently, in nests, characteristic vacuolated/foamy cytoplasm, pleomorphic nuclei, and inflamed stroma. All nAdSq showed block positivity for p16 like cAdSq. Significant portion of AdSq cases expressed the squamous marker p40 (58 % in nAdSq vs. 50 % in cAdSq). In contrast to pure adenocarcinomas or squamous cell carcinomas, 47 % (7/15) of nAdSq cases expressed both squamous and adenocarcinoma markers (p40 and BerEP4), with 5 (33 %) cases showing positivity for all four markers. Similarly, two cAdSq cases (22 %) showed universal positivity for all four markers, though p40 positivity was more focal and weaker in other instances. Despite morphological differences, the overall survival outcomes between nAdSq and cAdSq was not significantly different (p = 0.49). Many cervical carcinomas with diffuse growth pattern are likely the non-classic AdSq that do not contain spatially separate squamous and glandular components. Immunostaining may help in identifying this "non-classic" subtype of AdSq.

PIK3R1 acts as a prominent biomarker for tumor immune microenvironment modulation in intravenous leiomyomatosis

In current clinical practice, intravenous leiomyomatosis (IVL) can be surgically resected using either one-step or two-step approach. However, several challenges persist, including a high rate of postoperative recurrence, the difficulty in achieving complete resection in complex cases, and the inability to timely identify a substantial number of early-stage IVL cases. The mainstream theory regarding the pathogenesis and development mechanism of IVL is that it originates from uterine leiomyomas, yet the specific molecular mechanisms underlying this process remain to be elucidated. In this study, high-throughput transcriptome sequencing and molecular detection methods such as immunohistochemistry were employed to analyze the molecular expression differences at the transcriptome and immune microenvironment levels between 5 cases of IVL and paired uterine leiomyomas. These findings were subsequently validated in a cohort consisting of 45 IVL cases. The cross-enrichment analysis of differentially expressed genes (DEGs) at the transcriptome and immune level in paired samples yielded significant results. Notably, the up-regulated gene PIK3R1 and the down-regulated gene BMP4 emerged as two of the most critical representatives. Further investigation into the function of the PIK3R1 gene in IVL and its relationship with the immune microenvironment revealed that this gene was highly expressed in IVL and positively correlated with the abundance of plasma cells, while negatively correlated with follicular helper T cells and resting dendritic cells. The overall immune microenvironment of IVL was inactive, leading to tumor cells being less likely to be recognized and eliminated by immune cells. This study has conducted an in-depth analysis of the molecular expression, immune microenvironment characteristics, and related mechanisms of IVL. Further studies on larger cohort are warranted to demonstrate the potential value of inhibiting PIK3R1 as the adjuvant medicine for IVL therapy.

Assessment of trophoblast cell-surface antigen 2 (TROP2) and nectin-4 expression in choriocarcinoma

Choriocarcinoma is associated with high mortality in multiply relapsed patients. Herein, we assessed immunohistochemistry (IHC) expression of TROP2 and nectin-4 in choriocarcinoma and other germ cell tumors (GCT), as antibody drug conjugates (ADCs) targeting these markers are entering the therapeutic landscape of many tumors. Archival cases of choriocarcinoma and controls (non-choriocarcinoma GCT) were evaluated for TROP2 and nectin-4 IHC, performed on whole-slide sections, and results were quantified using H-scores (range: 0-300) based on membranous staining. The cohort included 20 primary GCT and 15 metastases from 34 patients. Of these, 18 specimens were choriocarcinoma (3 primary and 15 metastases), including six women with gestational choriocarcinoma. Median TROP2 and nectin-4 H-scores in choriocarcinomas were 22.5 and 60, respectively. For TROP2 and nectin-4, H-scores>200 were noted in 27.8% of patients, each. There was no correlation between serum beta-hCG levels measured within 2 weeks prior to specimen collection or peak serum beta-hCG levels and TROP2 or nectin-4 expression. The control group consisted of seminoma (n = 10); yolk sac tumor (n = 9), embryonal carcinoma (n = 10), postpubertal teratoma (n = 5), and spermatocytic tumor (n = 2). The median TROP2 H-scores for embryonal carcinoma, teratoma, and yolk sac tumor were 35, 30, and 15, respectively, and 0 for the remainder. The median nectin-4 H-score was 0 for all control group categories. Choriocarcinomas had a higher nectin-4 H-score compared to the control group (p < 0.001). Given the high TROP2 and nectin-4 expression in a subset of choriocarcinoma, ADCs targeting these biomarkers may be a promising therapeutic approach for these tumors, pending additional validation.

Hepatocyte nuclear factor 4α as a sensitive marker for uterine endocervical adenocarcinomas and their precursors

Hepatocyte nuclear factor (HNF)-4α is a marker of gastrointestinal tumor differentiation; however, its expression in endocervical tumors remains unclear. We aimed to assess the utility of HNF4α expression as a marker for endocervical adenocarcinomas (ECAs) and adenocarcinoma in situs (AISs), and to establish a minimal panel for distinguishing them from nonneoplastic endocervical glandular lesions and metastases. HNF4α expression was analyzed immunohistochemically (positive, H-score ≥10) in 323 tissue samples: 57 endocervical neoplasms including 35 glandular neoplasms and 22 squamous neoplasms, 144 nonneoplastic endocervical lesions, and 122 tumors from other organs. The panel for distinguishing endocervical glandular neoplasms from nonneoplastic glands and from metastases comprised HNF4α, p16, CDX2, and SATB2; staining was assessed. HNF4α was expressed significantly in ECAs and AISs, both HPV-independent and -associated types, but not in nonneoplastic glandular and squamous lesions (p < 0.05). The immunohistochemical detection sensitivity and specificity for endocervical ECA and AIS were 77% and 95%, respectively. For AIS alone, these were 79% and 94%, and for ECA alone, 75% and 94%, respectively. Either HNF4α(+) or p16(+) or double positive identified endocervical gland and squamous neoplasms (sensitivity, 96%; specificity, 76%). HNF4α(+) and SATB2(-) and CDX2(-) profiles suggested ECAs (sensitivity, 69%; specificity, 88%). HNF4α(+) and SATB2(+) or CDX2(+) profiles suggested adenocarcinomas of the gastrointestinal or genital tract (sensitivity, 81%; specificity, 88%). HNF4α is a promising marker for detecting both HPV-independent and -associated ECAs and AIS with high accuracy. Its combination with p16, CDX2, and SATB2 has potential use in diagnostic panels.

Performance of HER2 DAKO HercepTest and Ventana 4B5 immunohistochemical assays on detecting HER2 gene-amplification in uterine serous carcinomas

We compared the performance of two commonly-used HER2 immunohistochemistry (IHC) assays in uterine serous carcinomas (USC), correlating with HER2 gene amplification by fluorescence in-situ hybridization (FISH). Sixty-five USCs were stained by both HercepTest™ and PATHWAY 4B5 assays. FISH was performed by HER2 IQFISH pharmDx. Consensus HER2 IHC scoring was performed, and HER2 testing results were evaluated using USC-specific criteria. Complete concordance between HercepTest and 4B5 assays was achieved in 44/65 tumors (68%). The overall HER2 IHC/FISH concordance was 94% (45/48) by HercepTest and 91% (42/46) by 4B5. All HER2 IHC 3+ cases with HercepTest (n = 6) and 4B5 (n = 4) were gene-amplified, corresponding to specificities of 100%. For cases with IHC 2+, 41% (7/17) by HercepTest and 42% (8/19) by 4B5 had HER2 gene amplification. The sensitivity for HercepTest and 4B5 were 38% and 25%, respectively, at a cut-off of IHC 3+ (P = 0.50), and were 81% and 75%, respectively, at a cut-off of IHC 2+ (P > 0.99). Among HER2 IHC 0-1+ cases, 3/42 cases by HercepTest and 4/42 cases by 4B5 showed amplified FISH results, corresponding to overall false negative rates of 19% for HercepTest and 25% for 4B5. By using USC-specific IHC scoring criteria, both HercepTest and 4B5 assays showed high specificities (100%) for HER2 gene amplification in IHC 3+ cases, high IHC/FISH concordance, and comparable sensitivity for detecting HER2 gene amplification. The notable false negative rates using IHC 2+ as a cut-off for reflexing FISH analysis may warrant consideration for performing FISH in IHC 1+ cases until more data become available.

The sensitivity and specificity of Claudin18.2 and MUC6 in the differential diagnosis of endocervical gastric-type glandular lesions

Endocervical gastric-type adenocarcinoma (GAS) when well-differentiated or with less mucin may lead to misdiagnosis, particularly in biopsy specimens. This study aimed to evaluate the sensitivity and specificity of Claudin18.2 and MUC6 in the diagnosis of GAS and its precursor lesions. 167 cases from the Department of Pathology, Obstetrics and Gynecology Hospital of Fudan University (OGHFU) were selected, including 43 cases of usual type endocervical adenocarcinoma (UEA), 43 cases of GAS, 20 lobular endocervical glandular hyperplasia (LEGH) cases, 21 atypical LEGH (ALEGH) cases, and 40 normal/benign cases. A panel of immunohistochemical stains (IHC) for Claudin18.2, MUC6, P53, and P16 were performed on all cases. IHC expression in >5 % tumor cells was considered positive for Claudin18.2 and MUC6. An IHC composite score was calculated by multiplying the individual scores of extents by intensity. P53 was considered positive/mutant with the presence of strong nuclear reactivity in ≥75 % of cells (overexpression), was completely negative (null expression), or showed cytoplasmic staining. P16 was considered positive if diffuse block-type staining. Claudin18.2 was positive in all cases of LEGH and ALEGH and 83.7 % (36/43) GAS cases but was negative in all UEA and benign cases. MUC6 was positive in all LEGH and ALEGH cases, 88.4 % (38/43) of GAS cases, as well as 40.0 % (16/40) of benign and 20.9 % (9/43) of UEA cases. P53 mutant expression was found in 62.8 % (27/43) of GAS cases, 10 of which showed P16 diffuse staining and 10 of which were completely negative for P16. The composite scores of both Claudin18.2 and MUC6 were higher in ALEGH/LEGH than in GAS. Claudin 18.2 is a sensitive and specific marker for cervical gastric-type glandular lesions, not expressed in normal cervical tissues but expressed in all of the LEGH/ALEGH cases. However, it was not helpful in differentiating GAS from ALEGH. MUC6 is a highly sensitive marker for LEGH and GAS, yet its specificity is much lower than that of Claudin18.2. Taking morphology as the cornerstone and combining immunomarkers such as P16, P53, Claudin18.2 and MUC6 can significantly enhance the diagnostic efficiency of gastric-type glandular lesions.

Improving histotyping precision: The impact of immunohistochemical algorithms on epithelial ovarian cancer classification

To improve the precision of epithelial ovarian cancer histotyping, Köbel et al. (2016) developed immunohistochemical decision-tree algorithms. These included a six- and four-split algorithm, and separate six-split algorithms for early- and advanced stage disease. In this study, we evaluated the efficacy of these algorithms. A gynecological pathologist determined the hematoxylin and eosin (H&E)-based histotypes of 230 patients. Subsequently, the final histotypes were established by re-evaluating the H&E-stained sections and immunohistochemistry outcomes. For histotype prediction using the algorithms, the immunohistochemical markers Napsin A, p16, p53, progesterone receptor (PR), trefoil factor 3 (TFF3), and Wilms' tumor 1 (WT1) were scored. The algorithmic predictions were compared with the final histotypes to assess their precision, for which the early- and advanced stage algorithms were assessed together as six-split-stages algorithm. The six-split algorithm demonstrated 96.1% precision, whereas the six-split-stages and four-split algorithms showed 93.5% precision. Of the 230 cases, 16 (7%) showed discordant original and final diagnoses; the algorithms concurred with the final diagnosis in 14/16 cases (87.5%). In 12.4%-13.3% of cases, the H&E-based histotype changed based on the algorithmic outcome. The six-split stages algorithm had a lower sensitivity for low-grade serous carcinoma (80% versus 100%), while the four-split stages algorithm showed reduced sensitivity for endometrioid carcinoma (78% versus 92.7-97.6%). Considering the higher sensitivity of the six-split algorithm for endometrioid and low-grade serous carcinoma compared with the four-split and six-split-stages algorithms, respectively, we recommend the adoption of the six-split algorithm for histotyping epithelial ovarian cancer in clinical practice.

Different clinico-pathological and prognostic features of vulvar, vaginal, and cervical melanomas

Female genital tract melanoma (FGTM) is a rare and aggressive melanocytic malignancy, and its clinico-pathological and prognostic features at different anatomic sites have not yet been fully described. We retrospectively analyzed and compared the clinico-pathological data and survival outcomes of patients with primary lower genital tract melanoma enrolled between January 2005 and December 2020. We identified 95 patients with FGTM, of whom 46 had vulvar melanomas (VuM), 43 had vaginal melanomas (VaM), and six had cervical melanomas (CM). The clinical characteristics of all 95 cases, including symptoms, single or multiple primary lesions, clinical stage, surgery, and histopathological characteristics of 62 primary untreated cases, including pigmentation, predominant cytology, histological pattern, mitotic figures, and tumor-infiltrating lymphocytes of VuM, VaM, and CM, differed significantly. In comparison, only trend differences in molecular alternations were evident (p = 0.077). Disease-specific survival (DSS) was 30.7% at 5 years (46.5%, 25.6%, and 44.4% for VuM, VaM and CM, respectively). Seventy-one (85.5%) patients experienced FGTM recurrence. The median time to the first recurrence was 11 months, and VaM recurred earlier than VM and CM (16, 6, and 10 months for VuM, VaM, and CM, respectively, p = 0.038). A univariate analysis of 50 cases revealed the negative factors of disease-specific survival (DSS), including the location of the vagina and the presence of ulceration, and the negative factors of recurrence-free survival (RFS), including multiple lesions, the presence of ulceration, and the presence of lymphovascular invasion. Multiple lesions showed a borderline correlation with DSS. A multivariate Cox regression analyses of 50 cases revealed that the presence of ulceration was associated with shorter DSS and RFS (yes vs. no, Hazard Ratio = 2.400 and 2.716, respectively). Vaginal location showed a significant correlation with DSS (Hazard Ratio = 2.750, p = 0.024). In conclusion, vulval, vaginal, and cervical melanomas may differ in terms of their clinico-pathological features and associations with DSS and RFS. Ulceration and vaginal location were significantly associated with shorter DSS, and ulceration was associated with an increased risk of FGTM recurrence.

Comprehensive immunohistochemical analysis of the gastrointestinal and Müllerian phenotypes of 139 ovarian mucinous cystadenomas

Mucinous cystadenoma is one of the most common benign ovarian neoplasms. The immunophenotypes and histogenetic relationships of mucinous cystadenomas with a Müllerian-type epithelium have not been fully explored. We elucidated the direction of differentiation of the mucinous epithelium that constitutes mucinous cystadenomas. Special attention was paid to the existence of gastrointestinal (GI)-type mucinous epithelium, and its association with background Müllerian-type epithelium. Immunohistochemistry was performed in 139 cases of mucinous cystadenoma to evaluate the expression of Claudin-18 (CLDN18), a novel marker of gastric differentiation; CDX2, a marker of intestinal differentiation; and estrogen receptor (ER), a marker of Müllerian differentiation. We found that GI differentiation characterized by CLDN18 and/or CDX2 positivity was observed in mucinous epithelium of most mucinous cystadenomas (129/139 cases, 93%). In a subset of these cases, the tumor was composed of mucinous epithelium exhibiting an intermediate GI and Müllerian phenotype (CLDN18+/CDX2±/ER+). Of note, in 12 cases, a transition from background Müllerian-type epithelium to mucinous epithelium with GI differentiation was identified. A minor subset (6%) of mucinous cystadenomas was considered a pure Müllerian type because the epithelium exhibited a CLDN18-/CDX2-/ER + immunophenotype. In conclusion, mucinous cystadenomas consist of three major subtypes: GI, Müllerian, and intermediate types. Most mucinous cystadenomas are GI-type, and they should be considered a precursor of GI-type mucinous borderline tumors. The existence of intermediate-type mucinous cystadenomas, and areas of transition from Müllerian-type to GI-type epithelium suggest that GI-type mucinous epithelium can arise from Müllerian duct derivatives or surface epithelium exhibiting Müllerian metaplasia in the ovary.

Fluorescence in-situ hybridization assessment of spindle cell-rich testicular sex cord stromal tumors demonstrates multiple chromosomal gains across histologic subtypes

Spindle cell-rich testicular sex cord-stromal tumors (TSCSTs) comprise a group that includes mostly (but not exclusively): myoid gonadal stromal tumor (MGST), adult granulosa cell tumor (AGCT), and unclassified TSCST. These entities demonstrate histopathologic overlap, and prior genomic studies have failed to identify specific oncogenic drivers. Results of DNA sequencing suggest that different types of spindle cell-rich TSCSTs harbor a recurrent pattern of chromosomal gains. However, these results have not been validated by alternative methods and the extent of these changes within individual tumors remains unknown. We used a combination of commercially available fluorescence in-situ hybridization (FISH) probes (3q11.2, 6p24.3, 6q11.1, 6q23, 7q11.21-q11.22, 9p21.3, 11q13.3, 17p11.2) to enumerate a subset of chromosomes identified as altered (gained) in prior studies. We analyzed 10 cases (3 MGST, 4 unclassified TSCST, 3 AGCT), including 7 that had been previously sequenced. FISH demonstrated gains of chromosomes 3, 6, 7, 9, and 11 above the pre-established threshold (25%) in 50%, 80%, 70%, 20%, and 40% of cases, respectively, with gains of chromosome 17 being present in only 1 unclassified TSCST. The proportion of cells with chromosomal gains ranged from 26% to 60%. Tumors with available copy number data from prior genomic analyses showed a partial discordance between FISH and sequencing results. This study demonstrates that spindle-cell rich TSCSTs harbor a recurrent pattern of chromosomal gains, which are present in variable subsets of neoplastic cells. Further studies are needed to determine if these chromosomal changes represent a mechanism relevant for oncogenesis or a secondary event.

Expression of B7–H4 and IDO1 is associated with drug resistance and poor prognosis in high-grade serous ovarian carcinomas

High-grade serous ovarian carcinoma (HGSC) is the most lethal gynecologic malignancy. While immune checkpoint inhibitors against PD-L1 and CTLA-4 have shown significant effects in multiple tumor types, the response rate to single-agent immune checkpoint inhibitors is low in HGSC. Alternative biomarkers and targets must be identified to guide patient selection and new therapeutic strategies in HGSC. Here, we aim to investigate the clinical significance of novel immune modulators, including B7-H4, IDO1, Tim3, IL6, and IL-8, in patients with HGSC. A total of 48 patients with HGSCs, comprising 24 cases that were sensitive and 24 that were resistant to standard paclitaxel and carboplatin chemotherapy, were selected for our initial analysis. A NanoString assay including 33 immune-related genes was used to compare the expression of different immune regulatory molecules in the sensitive and resistant groups. Differentially expressed proteins were verified using multiplex immunohistochemical staining on tissue arrays of 202 patients with HGSCs who underwent primary surgery at MDACC. We analyzed the expression levels of immune checkpoints and compared expression profiles with clinicopathologic features including response, progression-free survival, and overall survival. HGSC tumors resistant to therapy expressed higher levels of B7-H4 (69.3%), IDO1 (71.8%), Tim3 (89.1%), and inflammatory factors IL-6 and IL-8, and expressed higher Tim3 in stromal components. High expression of B7-H4 and IDO1 was associated with significantly lower overall survival and progression-free survival. B7-H4 and IDO1 were co-expressed in 49.1% of studied cases. A panel of immunomodulatory proteins including B7-H4, IDO1, Tim3, IL-6, and IL-8 are expressed at high levels in HGSCs. These modulators represent novel targets to enhance immunotherapy in patients with HGSCs.

High glypican-3 expression characterizes a distinct subset of ovarian clear cell carcinomas in Canadian patients: an opportunity for targeted therapy

The expression frequency and distribution of glypican-3 (GPC3) was retrospectively assessed by immunohistochemistry in 316 accurately phenotyped ovarian clear cell carcinoma (OCCC) specimens from Canadian patients. The study aimed to evaluate the prevalence of this biomarker in OCCC in a mixed-ethnicity Canadian population and to evaluate associations of GPC3 expression with clinicopathological parameters. Tissue microarrays with napsin A or HNF1β positive and WT1-negative OCCC specimens were evaluated using a GPC3 antibody clone 1G12. Membranous, cytoplasmic, and Golgi pattern GPC3 expression was noted in 184 of 316 (58.2%) cases; 63 of 316 (20%) cases showed high GPC3 expression (>50% of tumor cells were positive). GPC3 expression was not associated with age, stage, and residual disease after primary surgery. High GPC3 expression did not correlate with a specific morphological pattern or the presence of endometriosis. Furthermore, GPC3 expression was not significantly associated with survival in the entire cohort. Statistically significant association of high GPC3 expression was noted with higher body mass index, napsin A positivity, estrogen receptor (ER) negativity, and ARID1A retention. In a stratified analysis by ARID1A status, high GPC3 expression was significantly associated with unfavorable outcomes in cases with loss of ARID1A (n=10; log rank p=0.0048). Women diagnosed with OCCC and high GPC3 expression were also more likely to receive adjuvant chemotherapy. Considering the tumor-specific membranous expression of GPC3 in 58% of cases and high interobserver reproducibility, GPC3 immunohistochemistry is a robust predictive test for inclusion in clinical trials for GPC3-targeted therapies for OCCC.

Endometrial gastric (gastrointestinal)-type mucinous adenocarcinoma: Diagnostic criteria, differential diagnosis, and molecular insights

Endometrial gastric (gastrointestinal)-type mucinous adenocarcinoma (EGMA) is a rare histologic subtype of endometrial carcinoma that is challenging to recognize as a distinct entity. Mucinous differentiation has been observed in endometrial carcinomas since the 1980s. However, the definitive characterization of endometrial carcinomas with mucinous differentiation has been unclear in the past. Since its formal inclusion in the latest 5th edition of the World Health Organization (WHO) Classification of Female Genital Tumors, and with increasing awareness of this rare entity, more case reports and studies on EGMAs have emerged in the recent years. Some studies sought to understand the expression of gastrointestinal immunohistochemical markers in neoplastic and/or normal endometrium, while others performed comprehensive clinicopathologic characterization of EGMAs, including their molecular characteristics. However, there still exist challenges in the diagnosis of EGMA, with considerable overlaps in morphologic features and immunohistochemical phenotype existing between EGMAs and the other differential diagnoses. This review sought to summarize the known clinical presentation, radiological findings and pathologic features of EGMA to date. We also discuss in detail the salient differential diagnoses to consider, and evaluate the utility of immunohistochemistry in the workup of this entity.

Survivin, sonic hedgehog, krüppel-like factors, and p53 pathway in serous ovarian cancer: an immunohistochemical study

Survivin was previously associated with tumor stage and grade in ovarian cancer and interfered with the tumor's drug sensitivity. In addition, Survivin expression was found to be regulated by the Sonic hedgehog (Shh) pathway, Krüppel-like factor (KLF) family proteins, and p53 pathway. The main aim of this study was to assess the prognostic values of immunohistochemical expression of Survivin, Klf5, Klf11, Shh, p53, p21, and Mdm2 in a cohort of high-grade ovarian serous cancers. Other aims were comparison between high- and low-grade ovarian serous cancer and between platinum-resistant and the other cases. The last aim was to assess the correlations among the immunohistochemical expression of the studied proteins. Retrospective cohort study to assess immunohistochemical expression of Survivin, Klf5, Klf11, Shh, p53, p21, and Mdm2 in a tissue microarray of primary tumor samples among 73 women affected by high-grade ovarian serous cancer and 9 by low-grade ovarian serous cancer. Klf5 and Shh cytoplasmic staining were associated with short overall survival (HR 6.38, 95% CI 2.25-18.01, P < .05 and 2.25, 95% CI 1.19-4.23, P < .05, respectively). In addition, cytoplasmic Klf5 staining, high Klf11, and p53 nuclear staining were associated with platinum resistance (P < .05). Cytoplasmic Shh score was significantly correlated to the immunohistochemical expression of Klf5, Klf11, Mdm2, and Survivin. Our data highlight the possible role of Klf5 and Shh as prognostic markers, meanwhile confirming the role of the KLF family proteins and p53 in ovarian cancer drug resistance. Moreover, Shh appeared to play an important role in the intracellular network of ovarian neoplasia.

Criteria for risk stratification of vulvar and vaginal smooth muscle tumors: a follow-up study with application to leiomyoma variants, smooth muscle tumors of uncertain malignant potential, and leiomyosarcomas

Data have shown that uterine diagnostic criteria are universal for smooth muscle tumors (SMTs) originating in the ovary, vulva, vagina, broad ligament, and other supportive connective tissue and that uterine criteria outperform site-specific criteria for vulvar and vaginal SMTs. Classic benign and malignant spindled SMTs were well represented in our recent study comparing uterine and site-specific criteria in vulvovaginal SMTs, but leiomyoma variants and smooth muscle tumors of uncertain malignant potential (STUMPs) were relatively few. Therefore, we evaluated additional leiomyoma variants, STUMPs, and leiomyosarcomas from 17 patients (10 vaginal and 7 vulvar). The 10 vaginal tumors (59%) comprised cellular leiomyoma (n = 2), leiomyoma with bizarre nuclei (n = 3), STUMP (n = 1), and leiomyosarcoma (n = 4). The 7 vulvar tumors (41%) comprised leiomyoma with bizarre nuclei (n = 3), STUMP (n = 1), and leiomyosarcoma (n = 3). Follow-up was available for 13 patients (76.5%) ranging from 1 to 97 months (mean: 17.3; median: 7). Follow-up for some patients with leiomyosarcoma was limited (≤4 months for 4 patients). One vaginal STUMP locally recurred after 19 months, and 2 patients diagnosed with leiomyosarcoma developed distant metastases. All remaining patients had either no evidence of disease at last follow-up (10 patients, 58.8%) or their status was unknown (4 patients, 23.5%). Uterine criteria are valid for vulvovaginal leiomyoma variants and STUMPs and more appropriately classified these tumors than site-specific criteria. Our combined findings from the current and previous studies support use of uterine diagnostic thresholds for the entire spectrum of vulvovaginal SMTs.

Neuroectodermal elements are part of the morphological spectrum of DICER1-associated neoplasms

Many sarcomas with DICER1 pathogenic variants (PVs) exhibit a characteristic morphology, including a subepithelial layer of malignant mesenchymal cells, areas of rhabdomyoblastic differentiation and cartilaginous and/or osseous elements. We report 5 DICER1-associated neoplasms (1 moderately to poorly differentiated Sertoli Leydig cell tumour and 4 sarcomas) containing variable amounts of neuroectodermal elements. The neoplasms predominantly involved or were in close proximity to the female genital tract (ovary, uterine corpus, abdominal and pelvic cavity) and occurred in females aged 14 months to 54 years. The neuroectodermal elements were characterised by solid and tubular/rosette-like patterns and variable immunoreactivity with SALL4 and neuroendocrine markers. In some cases, the neuroectodermal component was focal while in others it was exclusive. In one case, the focal neuroectodermal component within an ovarian Sertoli Leydig cell tumour resulted in extraovarian metastasis. In reporting these cases, we suggest that neuroectodermal elements, including pure neuroectodermal tumours, are part of the morphological spectrum of DICER1-associated neoplasms. It is important that pathologists recognize that a neuroectodermal component (often admixed with other elements) may be a feature of such neoplasms. This will facilitate appropriate tumour and/or germline testing which could lead to the identification of germline DICER1 PVs (DICER1 syndrome). Three of the patients we report were subsequently shown to have a germline DICER1 PV.

The occurrence and histopathological recognition of atypical endometriosis in patients with ovarian endometriosis – a retrospective cohort study

- Atypical endometriosis (AE) is considered a potential precursor of endometriosis-associated ovarian carcinoma (EAOC). Despite this, AE identification currently lacks established clinical implications and is not routinely incorporated in histopathological examinations of endometriosis. This study aimed to determine the interobserver variability in AE diagnosis and to classify the features that may attribute to consistent AE identification and diagnosis. - Cases of ovarian endometriosis, collected between 1985 and 2017 at the Radboud University Medical Centre Nijmegen, were identified using the PALGA database. Pathology reports were reviewed for descriptions of atypical features and mentions of AE. Using a predefined set of criteria adapted from the literature, two independent pathologists re-evaluated the 266 most recent ovarian endometriomas for AE. After revision, the pathologist revised cases with AE to reach consensus when discrepancies occurred. - Among 266 cases of ovarian endometriosis, AE was reported in 31 (11.7 %) cases. The revising pathologists identified AE in 48 cases (18 %), a number that was reduced to 19 cases (7.1 %) after a consensus meeting between the pathologist. After consensus was reached, the diagnostic criteria, adapted from the literature, were adjusted. DISCUSSION/FUTURE DIRECTIONS: - High interobserver variability likely reflects AE's heterogeneous presentation, the uncertain role of inflammation-driven atypia and AE's undefined clinical significance. However, given AE's association with malignant transformation, consistent identification may be essential. Stricter criteria were developed for AE in order to encourage uniform identification. Furthermore, we encourage adequate documentation of AE in order to increase the insight in endometriosis behavior by linking endometriosis subtypes to clinical progression.

GATA3 immunohistochemistry as a diagnostic adjunct for differentiated vulvar intraepithelial neoplasia: utility and limitations

Herein, the authors evaluate the diagnostic utility and limitations of GATA3 immunohistochemistry for the distinction of differentiated vulvar intraepithelial neoplasia (dVIN) from its potential mimics. Immunohistochemical studies for GATA3, p53, and p16 were performed on 124 pathologic vulvar tissues, inclusive of dVIN (n = 21), vulvar aberrant maturation (n = 10), high-grade squamous intraepithelial lesion (HSIL) (n = 44), and 49 non-neoplastic vulvar dermatoses of various types. GATA3 expression was scored using a modification of previously proposed criteria: pattern 0 (no significant loss of basal layer staining, >75% staining), pattern 1 (25-75% staining), and pattern 2 (<25% staining). With the exception of lichen sclerosus, 8% of which showed pattern 1 or 2 staining, all other non-neoplastic lesions showed pattern 0 expression. Aberrant GATA3 expression (i.e., patterns 1 or 2) was present in 90% of dVIN cases (2 [9.5%], 3 [14.3%], 16 [76.2%] with patterns 0, 1, and 2 respectively), 90% of vulvar aberrant maturation cases (1 [10%],7 [70%], 2 [20%] with patterns 0, 1, and 2 respectively), and 15.9% of HSIL cases (84.1% pattern 0; 2.3% pattern 1; 13.6% pattern 2). All HSIL cases were p16 positive, including the 7 pattern 1 and 2 cases. All cases of dVIN-like HSIL were pattern 0, and all (n = 2) cases of HSIL-like (basaloid) dVIN were pattern 2 (both of the latter cases displayed complete absence of epidermal staining). Only 1 dVIN case was both pattern 0 and p53-wild-type. We conclude that GATA3 is useful for the distinction of dVIN from non-neoplastic dermatoses and from HSIL, but is best used as part of a panel that includes p53 and p16 to mitigate its limitations.

Malignant rhabdoid tumors of the vulva versus epithelioid sarcomas: a clinicopathologic, immunohistochemical, and molecular genetics study

It has been suggested that most, if not all, extrarenal rhabdoid tumors of the vulva represent "proximal-type" epithelioid sarcomas. To better understand rhabdoid tumors of the vulva, we studied the clinicopathologic, immunohistochemical (IHC), and molecular features of 8 of these tumors and 13 extragenital epithelioid sarcomas. IHC analysis for cytokeratin AE1/AE3, EMA, S100, CD34, ERG, smooth muscle actin, desmin, and SMARCB1 (INI1) was performed. Ultrastructural study was done in one vulvar rhabdoid tumor. Next-generation sequencing of the SMARCB1 gene was performed in all cases. The 8 vulvar tumors occurred in adult women (mean age, 49 years). They were poorly differentiated neoplasms with a rhabdoid morphology. The ultrastructural study showed large amounts of intermediate filaments (10 nm). All cases had loss of expression of INI1 and were negative for CD34 and ERG. One case showed 2 SMARCB1 mutations: c.592C>T in exon 5 and c.782delG in exon 6. Follow-up revealed that 4 patients died of disease, 1 was alive with disease, and 3 were alive without evidence of disease. Epithelioid sarcomas occurred in young adults (mean age, 41 years), mostly men. Seven tumors arose in the distal extremities and the other 6 had a proximal location. They showed the characteristic "granulomatous" arrangement of the neoplastic cells. The recurrent tumors were more proximal and often showed a rhabdoid morphology. All cases had loss of expression of INI1. CD34 and ERG were expressed by 8 (62%) and 5 (38%) tumors, respectively. No SMARCB1 mutations were encountered. Follow-up revealed that 5 patients died of disease, 1 was alive with disease, and 7 were alive without evidence of disease. Based on their different morphology and biological behavior, we conclude that rhabdoid tumors of the vulva and epithelioid sarcomas are different diseases with distinct clinicopathologic features. Undifferentiated vulvar tumors with rhabdoid morphology should be classified as malignant rhabdoid tumors, rather than "proximal-type" epithelioid sarcomas.

Tumor budding activity is an independent prognostic factor in squamous cell carcinoma of the vulva

Tumor budding activity (TBA) is recognized as a potential prognostic factor in carcinomas from several anatomic sites. This study evaluates the prognostic value of TBA in a cohort of squamous cell carcinoma of the vulva (VSCC). TBA, defined as clusters of <5 tumor cells that are detached from the main tumor and that infiltrate into surrounding stroma, was assessed in 82 cases of surgically excised VSCC and correlated with patient outcomes. All cases were classified into one of 3 groups: no TBA, low TBA (1-14 foci), and high TBA (≥15 foci). Twenty-three (29.1%), 37 (45.1%), and 22 (26.8%) cases showed no, low, and high TBA, respectively. High TBA was associated with reduced overall survival (OS) on multivariate analysis independent of FIGO stage, human papillomavirus (HPV) status, and p53 status. The majority of tumors with high TBA displayed a p53 mutant staining pattern (77.3%, 17 of 22). The 17 patients whose tumors displayed a p53 mutant/high TBA profile had worse outcomes when compared with 15 patients whose tumors showed a p53 mutant/no TBA or p53 mutant/low TBA profile (mean OS 37.5 versus 63.3 months, respectively, P = .002). High TBA was observed in only 5 of 47 HPV-associated cases, and this subset also seemed to display a worse patient outcome as compared with the rest of the HPV-associated cohort (OS 16.8 versus 142.8 months, P < .0001). In summary, these findings indicate that TBA is an independent prognostic indicator in VSCC patients, and that high TBA is associated with worse clinical outcomes.

Clinicopathological features and molecular genetic changes in 17 cases of uterine tumor resembling ovarian sex cord tumor

Uterine tumor resembling ovarian sex cord tumor (UTROSCT) is a rare mesenchymal neoplasm that was recently reported to exhibit recurrent NCOA1-3rearrangement with the most frequent partners ESR1 and GREB1. In this study, the clinicopathological characteristics of 17 UTROSCT cases were summarized; among them, the fusion genes of 12 cases were retrospectively analyzed by targeted RNA sequencing. The mean age of our cohort was 47 years (19-67 y). Although the majority of UTROSCTs had clear boundaries on gross examination, microscopic infiltration into the myometrium was observed in 82.4 % of cases. The tumor cells showed diffuse, trabecular, nested, reticular, pseudopapillary, hollow and solid tubular patterns, expressing sex cord, epithelial, and myogenic markers. Six fusion genes, including ESR1::NCOA3 (n = 4), ESR1::NCOA2 (n = 2), ESR1::CITED2 (n = 2), GREB1::NCOA2 (n = 2), GREB1::NCOA1 (n = 1), and GREB1::NCOA3 (n = 1), were identified. The fusion genes of the three cases with recurrence and metastasis were GREB1::NCOA2, ESR1::NCOA3, and ESR1::CITED2. All 3 cases of recurrent tumors showed infiltrative growth, with moderate to severe dysplasia of tumor cells and different degrees of rhabdomyoid differentiation. This is the first report of the ESR1::CITED2 fusion genes in UTROSCT, and one of the two patients had recurrence and metastasis. Compared with UTROSCT withESR1 rearrangement, UTROSCT with GREB1 rearrangement was more common in elderly patientsand was more likely to present with intramural masses, less sex cord differentiation, poor prognosis, and relapse and metastasis.

Discordance of microsatellite instability and mismatch repair immunochemistry occurs depending on the cancer type

Microsatellite instability (MSI) and deficiency of mismatch repair (dMMR) are key markers for predicting the response of immune checkpoint inhibitors (ICIs) and screening for Lynch syndrome (LS). This study examined the incidences of and factors associated with the concordance of MSI and MMR in human cancers. A total of 518 formalin-fixed cancer tissues were analyzed for MSI and MMR immunohistochemistry (IHC). MSI was analyzed by a PCR-based method using Promega markers. Concordance with MMR expression and factors associated with concordance were analyzed. In 2 colorectal cancer samples, MMR IHC failed due to inadequate staining conditions. In the remaining 516 cancers, a high level of MSI (MSI-H) was identified in 113 cases, and dMMR was identified in 112. The concordance of MSI and MMR IHC was 98.3%. Only 9 cases (4 pancreatobiliary, 3 colorectal, and 2 endometrial cancers) were discordant. Of the 113 MSI-H cases, 4 (3.5%) were proficient MMR (pMMR); of the 403 microsatellite stability (MSS) cases, 5 (1.2%) were dMMR. The independent factors associated with MSI-H/dMMR included meeting Amsterdam II criteria, assay purpose, and sampling method. Multivariate analysis revealed that cancer type (gastrointestinal cancers or others) was associated with concordance of MSI and MMR IHC. Three LS cases with pancreatic or endometrial cancer demonstrated MSS and dMMR, and one biliary cancer showed MSI-H and pMMR. Discordance between MSI and MMR IHC occasionally occurs in pancreaticobiliary and endometrial cancers. When suspected, both MSI and MMR IHC should be done to judge the ICI indication and screen for LS.

Intestinal and liver involvement by endometrial stromal sarcoma: Expanding the differential diagnosis of mesenchymal tumors involving the GI tract

Endometrial stromal sarcoma (ESS) is a mesenchymal tumor known for infiltrative growth and lymphovascular invasion. Most examples arise in the endometrium, but some occur in the abdominal cavity without a primary uterine lesion, likely originating from endometriosis. ESS involving the gastrointestinal (GI) tract and liver is rare. We reviewed 15 examples from 13 women between 2010 and 2023. The mean age was 51 (range 16-81); just over half of the patients (7/13, 54 %) had a history of uterine ESS. Twelve tumors involved the intestines and three the liver; rectosigmoid colon was the most affected site. Tumors averaged 4.6 cm (range 0.3-10 cm) and involved all bowel layers with two showing transmural involvement. Predominantly low-grade features were observed, including uniform round to spindle cells in fibrous or myxoid stroma, permeative growth, hyaline plaques, and spiral arterioles. Endometriosis was seen in 4 (27 %) cases. Immunohistochemical analysis revealed positivity for ER (93 %), PR (92 %), CD10 (91 %), and focal cyclin D1 (80 %). A minority of cases showed staining with smooth muscle markers, CD117, DOG1, and keratins. High-grade features were suggested but not diagnostic in three cases. Follow-up data for three patients showed one death at 16 months, one patient disease-free at 94 months, and another alive at 16 months. ESS involving the GI tract is rare, may lack a uterine primary, and can mimic other neoplasms due to keratin, smooth muscle, and CD117/DOG1 expression. Recognizing ESS-associated features-such as a permeative pattern, hyaline plaques, and spiral arterioles-is key to avoiding misdiagnosis.

Ovarian high-grade serous carcinoma with transitional-like (SET) morphology: a homologous recombination-deficient tumor

Thirteen years ago, we pointed out that ovarian transitional cell carcinomas (TCCs) and conventional high-grade serous carcinomas (HGSCs) had similar genetic alterations and clinical behavior. Consequently, ovarian TCC is now classified as a morphologic variant of HGSC. Defective homologous recombination, resulting from genetic or epigenetic inactivation of DNA damage repair genes, such as BRCA1/2, occurs in approximately 50% of the HGSCs. Although BRCA mutations have been associated with HGSCs with solid, pseudoendometrioid or transitional (SET) features, little is known about the role of non-BRCA homologous recombinationrepair (HRR) genes and the HRR status in these tumors. Using two commercially available assays (Myriad Genetics MyChoice CDx Plus test and SOPHiA Dx Homologous Recombination Deficiency Solution), we study mutations of BRCA1/2 and non-BRCA HRR genes (ATM, BARD1, BRIP1, CDK12, CHEK1/2, FANCL, PALB2, PPP2R2A, RAD51B, RAD51C, RAD51D, and RAD54L), and the HRR status in 19 HGSCs with SET features and 20 HGSCs with classic morphology. We also studied, as control cases, 5 endometrioid carcinomas, 1 clear cell carcinoma, 2 low-grade serous carcinomas, and 1 malignant Brenner tumor. Seven HGSCs with SET features (7/19; 37%) showed BRCA mutations (4 BRCA1, 2 BRCA2, and 1 BRCA1/2). Mutations in non-BRCA HRR genes were found in ATM (1/15; 7%), BARD1 (1/15; 7%), and BRIP1 (1/19; 5%). Most HGSCs with SET features (17/19; 90%) were considered to be homologous recombination-deficient tumors. Three HGSCs with classic morphology (3/20; 15%) showed BRCA2 mutations. Mutations in non-BRCA HRR genes were found in CDK12 (2/14; 14%), FANCL (1/14; 7%), RAD51B (1/14; 7%), and RAD54L (1/14; 7%). Eleven HGSCs with classical morphology (11/20; 55%) were considered to be homologous recombination deficient. In contrast, all ovarian carcinoma control cases (5 endometrioid carcinomas, 1 clear cell carcinoma, 2 low-grade serous carcinomas, and 1 malignant Brenner tumor) were homologous recombination proficient and did not have BRCA mutations. Our results show that the majority of HGSCs with SET features are homologous recombination-deficient tumors independently of the BRCA status and highlight the importance of the HRR tumor testing, especially in BRCA wild-type tumors. Recognition of transitional cell variant of HGSCs may help to identify patients most likely to benefit from PARP inhibitors.

Pathologic, immunologic, and clinical analysis of the microsatellite instability phenotype in endometrial carcinoma

The objective of this study was to determine if quantifying the microsatellite instability (MSI) phenotype could serve as a biomarker for clinical and immunologic features of deficient mismatch repair (dMMR) endometrial cancer (EC). Patients with EC undergoing hysterectomy whose tumors demonstrated dMMR were included. Immunohistochemistry (IHC) of mismatch repair proteins and polymerase chain reaction analysis of NR27, BAT25, BAT26, NR24, and NR21 microsatellite loci were performed on each case. The MSI phenotype was quantified by subtracting the number of nucleotides of each microsatellite in tumor tissue from the corresponding microsatellite in paired normal tissue and summing the absolute differences. This was termed marker sum (MS) and is a novel quantification. Tumor-infiltrating lymphocytes (TILs) were identified by IHC for CD3, CD4, and CD8 and quantified with digital image analysis. Tumor infiltration of lymphocytes and clinical characteristics were stratified by MS. Four hundred fifty-nine consecutive patients with dMMR EC were analyzed. MS ranged from 1 to 32. Post hoc, 2 cohorts were defined using receiver operating characteristic curves (MS less than 13 and MS greater than 12). With the exception of tumor grade, all clinical and pathologic features, all tumor characteristics, and the numbers of TILs were similar between cohorts. The MSI phenotype is highly variable in dMMR EC, and no correlation between the immune profile and the severity of the MSI phenotype was observed.

Frequency of HER2 protein overexpression and HER2 gene amplification in endometrial clear cell carcinoma

HER2 (ERBB2) overexpression and/or HER2 gene amplification has been well established in several tumors types and when present HER2 directed therapy may be to be efficacious. While recent findings suggests that HER2 overexpression and HER2 amplification are a relatively common in serous endometrial carcinoma, similar data regarding clear cell endometrial carcinoma (CCC) is difficult to interpret due to issues such as diagnostic criteria, sample type and HER2 interpretation criteria. Our goals were to study HER2 expression and HER2 copy number status in hysterectomy specimens from a large series of patients with pure CCC to determine the frequency of HER2 overexpression and HER2 amplification and evaluate applicability of current HER2 interpretation criteria. Pure CCC specimens derived from hysterectomy specimens from 26 patients were identified. All diagnoses were confirmed by two gynecologic pathologists. Immunohistochemistry for HER2 protein and fluorescence in situ hybridization (FISH) studies for HER2 were performed on whole-slide sections from all cases. Results were interpreted according to the 2018 ASO/CAP HER2 guidelines for breast cancer and International Society of Gynecologic Pathologists (ISGyP) HER2 guidelines for serous endometrial carcinoma. Additional testing was performed when indicated by the guidelines. HER2 expression by immunohistochemistry was 3+ in 4% and 0% of cases, and 2+ in 46% and 52% of cases, by 2018 ASCO/CAP and ISGyP criteria, respectively, while the remaining cases were negative. HER2 testing by FISH showed a positive result in 27% of tumors with 2018 ASCO/CAP guidelines, while 23% were positive with the ISGyP criteria. Our findings indicate that HER2 overexpression and HER2 amplification occur in a subset of CCC. Therefore, additional study into the potential benefit of HER2 targeted therapy in patients with CCC is warranted.

The value of SOX2 in the differential diagnosis of SMARCA4 (BRG1)-deficient uterine neoplasms

SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4/BRG1)-deficient undifferentiated uterine sarcoma (SDUS) is a recently described uterine sarcoma. It is characterized by predominantly rhabdoid or large epithelioid cells with abundant cytoplasm and varying components of small and spindle cells, resembling the 'large cell variant' of small cell carcinoma of the ovary, hypercalcemic type (SCCOHT). In addition, SMARCA4-inactivating mutations have been described as the driver mutations in SDUS. However, undifferentiated endometrial carcinoma (UDEC) and dedifferentiated endometrial carcinoma (DDEC) may show some clinical and morphological overlaps with SDUS, and about 20% of reported UDEC/DDEC cases also have loss expression of SMARCA4. SDUS is a very aggressive disease and universally lethal in all reported cases. Differentiating SDUS from UDEC/DDEC is relevant for the prognosis, pathogenesis, and possible targeted therapies for the disease. In this study, we compared the clinical, morphological, immunohistochemical, and molecular characteristics of 10 tumors including 2 SDUS, 2 SCCOHT, 1 uterine carcinoma with neuroendocrine differentiation (UDEC?), and 5 UDEC/DDEC. All 5 UDEC/DDEC cases showed strong and diffuse nuclear positivity for SOX2, while all SCCOHT and SDUS cases were completely negative. We concluded that SOX2 could be a useful marker for the differential diagnosis between SDUS and UDEC/DDEC.