Archives of Pathology & Laboratory Medicine

Metastatic Malignancies to the Ovaries

Context.— Between 5% and 30% of malignant neoplasms involving the ovary are metastatic. A variety of neoplasms can metastasize to the ovary, including those from the colorectum, endometrium, breast, appendix, stomach, and cervix. Objective.— To summarize the clinical, gross, and histologic features that aid in distinguishing primary ovarian neoplasms from metastatic neoplasms. Additionally, to discuss the immunohistochemical features that help identify the primary site of origin. Data Sources.— Sources include literature review and cases identified from the authors’ practice. Conclusions.— There are many features that can help distinguish a primary ovarian neoplasm from a metastatic lesion. The patient’s clinical symptoms and history may suggest the primary site. On radiology, the absence of ascites is suggestive of metastasis. Laboratory tests such as cancer antigen 125 (CA 125) and carcinoembryonic antigen (CEA) are helpful in distinguishing a primary versus metastatic neoplasm. Gross features that favor metastasis are bilaterality and small tumor size. Metastatic lesions often have multinodular growth and involve the surface or superficial cortex. Histologic features favoring metastasis include a nodular or infiltrative pattern, stromal desmoplasia, hilar involvement, lymphovascular invasion, and an absence of benign or borderline components. The presence of extracellular mucin and signet ring cells also suggests metastasis. Distinct histologic features can be suggestive of the primary site. Immunohistochemical stains, such as cytokeratin (CK) 7, CK20, SATB homeobox 2 (SATB2), p16, paired box 8 (PAX8), WT1 transcription factor (WT1), estrogen receptor (ER), progesterone receptor (PR), and GATA-binding protein 3 (GATA3), can also be useful in evaluating the site of origin. Distinguishing between a primary ovarian tumor and metastasis is critical for determining prognosis and treatment.

Reporting Subclonal Immunohistochemical Staining of Mismatch Repair Proteins in Endometrial Carcinoma in the Times of Ever-Changing Guidelines

Context.— The current College of American Pathologists reporting guideline for mismatch repair protein (MMRP) immunohistochemistry for Lynch syndrome (LS) screening considers the presence of any positive nuclear staining as intact MMRP expression. This would include tumors with combined areas of subclonal retention and loss of MMRP staining. Objective.— To evaluate the clinical significance of reporting subclonal staining patterns of MMRP immunohistochemistry in endometrial carcinoma. Design.— We retrospectively reviewed 455 consecutive MMRP immunohistochemistry results of endometrial carcinoma in hysterectomy specimens from 2012 through 2017 and identified cases with subclonal MMRP staining. These results were correlated with the patient's personal and family history of LS-associated carcinoma, MLH1 promoter methylation status, and LS genetic testing. Results.— Subclonal staining of MMRP was seen in 48 of 455 cases (10.5%) on review. Thirty cases demonstrated isolated subclonal staining and were reported by pathologists as follows: subclonal (n = 5), complete MMRP loss (n = 4), and intact MMRP (n = 21). Eighteen cases had subclonal staining in combination with complete loss of other MMRP. Cases reported as subclonal or complete MMRP loss had appropriate clinical follow-up. Two of 2 cases with isolated subclonal MSH6 loss tested positive for LS. One of 3 cases with isolated subclonal MLH1/PMS2 loss was negative for MLH1 promoter methylation; LS genetic testing was not performed because of cost. Conclusions.— Our study reveals that LS germline mutation can be detected in endometrial carcinoma patients whose tumors display sole subclonal MMRP staining. Our results stress the importance of reporting subclonal staining patterns to ensure appropriate clinical follow-up.

HER2 Testing in Endometrial Serous Carcinoma: Time for Standardized Pathology Practice to Meet the Clinical Demand

Context.— Endometrial serous carcinoma is an aggressive subtype of endometrial cancer with the highest rate of recurrence and mortality among all histotypes. A recent clinical trial showed prolonged progression-free survival in advanced-stage and recurrent human epidermal growth factor receptor 2 (HER2)–positive endometrial serous carcinoma when trastuzumab was added to the standard chemotherapy regimen. This targeted therapeutic approach was recently endorsed by the National Comprehensive Cancer Network clinical guidelines. There is a growing interest among clinicians to obtain HER2 testing in endometrial serous carcinoma, and pathologists need to be prepared to recognize the unique characteristics of HER2 protein expression and gene amplification in these tumors and apply specific HER2 scoring criteria. Objective.— To provide a historical overview of targeted HER2 therapy in endometrial serous carcinoma and to summarize key findings from recent studies on the specific features of HER2 protein expression and gene amplification relative to other tumor types. Endometrial carcinoma–specific HER2 testing criteria are proposed based on evidence in the existing literature. Data Sources.— Sources comprise review of the literature and personal experience of the author. Conclusions.— HER2 protein overexpression and/or gene amplification is present in approximately 25% to 30% of endometrial serous carcinomas, providing an opportunity for targeted therapy. Pathologists play a key role in tumor HER2 testing and scoring to ensure appropriate patient selection and successful clinical outcome.

Practice Patterns Regarding Quality Assurance Measures in Gynecologic Cytology: Survey Results of Laboratories Participating in the 2022 College of American Pathologists PAP Education Program

Context.— Though numerous quality assurance (QA) measures are in place for the practice of gynecologic cytopathology, many of them are not clearly defined and may be variably used by laboratories worldwide. Objective.— To assess current practice patterns regarding the implementation of selected gynecologic cytology QA metrics to help develop guidance for laboratories. Design.— A supplemental questionnaire was mailed to laboratories participating in the 2022 College of American Pathologists (CAP) Gynecologic Cytopathology (PAP Education) Program requesting data regarding their QA measures in gynecologic cytology. Results.— A total of 562 laboratories responded to the supplemental questionnaire; responses from 511 laboratories were analyzed further. Of 492 laboratories, most considered Papanicolaou (Pap) tests from patients with untreated abnormal cytology in the previous year (386; 78.5%) or with an abnormal gynecologic biopsy finding (concurrent or within the past year) (331; 67.3%) as high-risk for negative rescreening. Many laboratories (436 of 511; 85.3%) required pathologist review of Pap tests for indications other than reactive/abnormal cells (eg, endometrial cells in women 45 years of age and older). For assessing cytologists’ performance, 88.5% (399 of 451) of respondents recorded the discrepancy rate between cytologist’s and pathologist’s interpretations. For monitoring pathologists’ performance, most laboratories (243 of 389; 62.5%) evaluated cases with significant cytologic-histologic discrepancy. Conclusions.— The CAP survey provided a detailed assessment of current QA practices regarding gynecologic cytology, which can aid laboratories in making decisions related to enhancement of QA in their setting. As the guidelines and tools for cervical cancer screening evolve, QA metrics will need to be accordingly refined.

Gestational Choriocarcinoma: A Timely Review of Diagnostic Pathology

Context.— Gestational choriocarcinoma is the most common form of gestational trophoblastic neoplasm. It is characterized by aggressive, destructive growth and a marked tendency for hematogenous spread, leading to high mortality if left untreated. However, with the advent of effective clinical treatment for postmolar gestational trophoblastic neoplasms in recent decades, the clinicopathologic presentation of gestational choriocarcinoma has significantly changed. Today, it more frequently presents at extrauterine sites and/or in an unexpected manner, posing considerable diagnostic challenges for pathologists. Nonetheless, prompt and accurate pathologic diagnosis remains essential for effective clinical management and optimal patient outcomes. Objective.— To review the clinical features and pathologic diagnosis of gestational choriocarcinoma, including its early manifestations. Data Sources.— This review is based on literature and the author’s personal diagnostic experience. Conclusions.— In the era of precision medicine, gestational choriocarcinoma has become a rare encounter, largely owing to the implementation of postmolar surveillance programs and timely initiation of chemotherapy. Diagnostic recognition of the tumor requires a high index of suspicion, familiarity with its histologic features and early forms, awareness of the unexpected extrauterine presentations, and appropriate use of immunohistochemical and molecular biomarkers. These tools are essential in distinguishing gestational choriocarcinoma from nongestational mimics of germ cell or somatic origin, which have profound therapeutic and prognostic implications.

Biomarkers in Cervical Squamous Neoplasia: Diagnostic, Prognostic, and Predictive

Context.— Cervical squamous neoplasia runs the gamut from low-risk intraepithelial processes to aggressive invasive malignancies. A variety of biomarkers can be enlisted to help diagnose, prognosticate, and inform treatment of these lesions. There are ongoing controversies about diagnostic and prognostic biomarker use in squamous intraepithelial lesions, and many pathologists are new to predictive biomarker interpretation in invasive cervical lesions. Objective.— To provide practical guidance on the appropriate use of diagnostic, prognostic, and predictive biomarkers in cervical squamous intraepithelial lesions and invasive carcinomas. Data Sources.— Peer-reviewed literature and the author’s personal experience. Conclusions.— Diagnostic biomarkers such as p16 and human papillomavirus E6/E7 messenger RNA in situ hybridization can have value in the diagnosis of squamous intraepithelial neoplasia, but there are important caveats to their use and interpretation. No prognostic biomarkers have yet demonstrated statistically durable significance for risk stratification of low-grade squamous intraepithelial lesions. Programmed death ligand-1 immunohistochemistry and tumor mutational burden testing are US Food & Drug Administration–approved predictive biomarkers that can be enlisted for the identification of invasive cervical squamous carcinomas that may respond to checkpoint inhibitor–based immunotherapy, whereas human epidermal growth factor receptor 2 (HER2) immunohistochemistry can identify optimal candidates for conjugated anti-HER2 therapies.

Outcomes and Management of Atypical Squamous Cells–Cannot Exclude High-Grade Squamous Intraepithelial Lesion in a Primary Human Papillomavirus Screening System

Context.— “Atypical squamous cells–cannot exclude high-grade squamous intraepithelial lesion” (ASC-H) cytology is uncommon (0.16%–0.43%). The reported risk of high-grade dysplasia varies greatly (12.00%–70.00%), making management challenging. Primary human papillomavirus (HPV) screening requires an updated understanding of ASC-H. Objective.— To review ASC-H colposcopic and histologic comparators, and management outcomes, to help guide future management. Design.— A 1-year retrospective analysis of new ASC-H–associated visits to a large colposcopy unit in Ireland in 2022 was performed. Results.— The incidence of new ASC-H referrals was 3.63% (97 of 2672). The sensitivity of colposcopy for detection of high-grade changes (cervical intraepithelial neoplasia [CIN]2 + ) is 69.39% (34 of 49) and the specificity is 43.18% (19 of 44). The positive predictive value is 64.15% (34 of 53) and the negative predictive value is 37.50% (15 of 40). High-grade dysplasia was identified in 53.26% (49 of 92) and adenocarcinoma in situ in 2.17% (2 of 92) of cases. Excisional treatment was performed for 52.58% (51 of 97) and cold coagulation for 12.37% (12 of 97) of cases. The test-of-cure result was HPV negative for 84.13%. High-risk HPV and abnormal cytology was seen in 9.52% (6 of 63) of cases, thus all required a second test-of-cure smear. Conclusions.— ASC-H with high-risk HPV has a 55.43% (51 of 92) risk of high-grade dysplasia, thus timely colposcopy and biopsy is imperative. Treatment was curative in 84.13% (53 of 63) to 96.83% (61 of 63) of cases, so it is an effective management strategy. Conservative management of selected cases may be a reasonable option.

A Population-Based Study of Patients With Small Cell Carcinoma of the Ovary, Hypercalcemic Type, Encompassing a 30-Year Period

Context.— Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare and lethal tumor, characterized by hypercalcemia and early onset and associated with germline and somatic SMARCA4 variants. Objective.— To identify all known cases of SCCOHT in the Slovenian population from 1991 to 2021 and present genetic testing results, histopathologic findings, and clinical data for these patients. We also estimate the incidence of SCCOHT. Design.— We conducted a retrospective analysis of hospital medical records and data from the Slovenian Cancer Registry in order to identify cases of SCCOHT and obtain relevant clinical data. Histopathologic review of tumor samples with assessment of immunohistochemical staining for SMARCA4/BRG1 was undertaken to confirm the diagnosis of SCCOHT. Germline and somatic genetic analyses were performed using targeted next-generation sequencing. Results.— Between 1991 and 2021, we identified 7 cases of SCCOHT in a population of 2 million. Genetic causes were determined in all cases. Two novel germline loss-of-function variants in SMARCA4 LRG_878t1:c.1423_1429delTACCTCA p.(Tyr475Ilefs*24) and LRG_878t1:c.3216-1G>T were identified. At diagnosis, patients were ages 21 to 41 and had International Federation of Gynecology and Obstetrics, or FIGO, stage IA-III disease. Outcomes were poor, with 6 of 7 patients dying of disease-related complications within 27 months from diagnosis. One patient had stable disease for 12 months while receiving immunotherapy. Conclusions.— We present genetic, histopathologic, and clinical characteristics for all cases of SCCOHT identified in the Slovenian population during a 30-year period. We report 2 novel germline SMARCA4 variants, possibly associated with high penetrance. We estimate the minimal incidence of SCCOHT to be 0.12 per 1 million per year.

Concordance Between Biopsy and Resection Diagnoses of Uterine Cervical Adenocarcinoma According to the Updated World Health Organization 2020 Classification: A Multi-Institutional Study Elucidating Real-World Practice in Japan

Context.— Endocervical adenocarcinoma is divided into human papillomavirus (HPV)-associated (HPVA) and HPV-independent (HPVI) in the 5th edition of the World Health Organization (WHO) tumor classification launched in 2020. However, the validity of the morphologic criteria used for biopsy specimens in real-world practice remains undetermined. Objective.— To validate the utility of the 5th edition of the WHO classification for biopsy samples, focusing on its diagnostic criteria with the aid of ancillary studies. Design.— We retrieved 217 cases of endocervical adenocarcinoma from 6 institutions, in which glass slides of both biopsy and resection specimens were available for review. Concordance between the biopsy and resection specimen diagnoses was evaluated. For discordant diagnoses, an algorithmic approach with ancillary studies proposed by the international group was applied to confirm their utility to improve the accuracy of biopsy diagnosis. Results.— The biopsy diagnosis matched the resection specimen diagnosis in 197 cases (concordance rate, 91%; κ = 0.75). The concordance rate was significantly higher for HPVA than HPVI (95% versus 81%, P = .001). There were no significant differences in the proportions of HPVA and HPVI or the accuracy of biopsy diagnosis between the participating institutions. All 19 discordant cases with unstained glass slides available were accurately recategorized as HPVA or HPVI using HPV in situ hybridization; p16 immunohistochemistry was positive in 3 of 9 cases of gastric-type HPVI that were negative by in situ hybridization. Conclusions.— The 5th edition of the WHO criteria for biopsy diagnosis of endocervical adenocarcinoma distinguishes HPVA from HPVI well when ancillary studies are adequately applied.

Clinical Decision Support for Ovarian Carcinoma Subtype Classification: A Pilot Observer Study With Pathology Trainees

Context.— Clinical decision support (CDS) systems could assist less experienced pathologists with certain diagnostic tasks for which subspecialty training or extensive experience is typically needed. The effect of decision support on pathologist performance for such diagnostic tasks has not been examined. Objective.— To examine the impact of a CDS tool for the classification of ovarian carcinoma subtypes by pathology trainees in a pilot observer study using digital pathology. Design.— Histologic review on 90 whole slide images from 75 ovarian cancer patients was conducted by 6 pathology residents using: (1) unaided review of whole slide images, and (2) aided review, where in addition to whole slide images observers used a CDS tool that provided information about the presence of 8 histologic features important for subtype classification that were identified previously by an expert in gynecologic pathology. The reference standard of ovarian subtype consisted of majority consensus from a panel of 3 gynecologic pathology experts. Results.— Aided review improved pairwise concordance with the reference standard for 5 of 6 observers by 3.3% to 17.8% (for 2 observers, increase was statistically significant) and mean interobserver agreement by 9.2% (not statistically significant). Observers benefited the most when the CDS tool prompted them to look for missed histologic features that were definitive for a certain subtype. Observer performance varied widely across cases with unanimous and nonunanimous reference classification, supporting the need for balancing data sets in terms of case difficulty. Conclusions.— Findings showed the potential of CDS systems to close the knowledge gap between pathologists for complex diagnostic tasks.

Accuracy and Reproducibility of Frozen Section Diagnosis in Ovarian Tumors

Context.— Intraoperative consultation—frozen section diagnosis (FSD)—determines tumor pathology and guides the optimal surgical management of ovarian neoplasms intraoperatively. Objective.— To evaluate the diagnostic accuracy of the FSD and analyze the discrepancy between the FSD and final diagnosis. Design.— This is a retrospective study of 618 ovarian neoplasm FSDs from 2009 to 2018 at a tertiary health care center. The discrepant cases were reviewed and reevaluated by gynecologic and general surgical pathologists. The outcomes of interest were performing unnecessary procedure, returning for a second surgery, and 30-day postoperative mortality. Results.— The sensitivity and the positive predictive value of the FSD were lower in borderline tumors than in benign and malignant epithelial ovarian tumors. Major and minor discrepancies were identified in 5.3% (33 of 618) and 12.3% of (76 of 618) cases, respectively. A root cause analysis of the major discrepant cases showed that sampling error accounted for 43% (14 of 33). The discrepancy distributions of gynecologic and general surgical pathologists were statistically similar in the overall cohort (P = .65). The overall κ for diagnostic agreement among gynecologic pathologists, general surgical pathologists, and final diagnosis was 0.18 (0.10–0.26, P < .001), implying only a slight overall agreement. Of the major discrepant cases, only 3 had a clinical implication. One overdiagnosed patient underwent an unecessary procedure, and 2 underdiagnosed patients were recommended to return for a second surgery. No patient had 30-day postoperative mortality. Conclusions.— Frozen section diagnosis remains a definitive diagnostic tool in ovarian neoplasms and plays a crucial role in guiding intraoperative surgical management.

Histologic Reaction Patterns of Lymph Node Involvement in Ovarian Serous Borderline Tumors: Their Implications for Prognosis

Context.— Lymph node (LN) involvement (LNI) is not infrequently observed in ovarian serous borderline tumors (SBTs) but is not considered equivalent to malignant tumor metastasis, as it reportedly does not impact recurrence or survival in patients with SBT. However, the reasons underlying the insignificant clinical impact of LNI remain unclear. Objective.— To determine whether histologic reaction patterns (HRPs) are associated with SBT prognosis. Design.— We compared HRPs around tumor cell clusters in LNs of patients with SBT and low-grade serous carcinoma. HRPs were classified into 4 categories (HRP 1–HRP 4) based on tumor cell location in LNs, the presence of their adhesion to surrounding lymphoid tissue, or pericellular desmoplastic reactions. Results.— Although LNI itself was linked to reduced recurrence-free survival (RFS), no recurrence was observed in patients with HRP 1 or 2, characterized by freely floating tumor cells in the lumens of afferent/efferent lymphatics or intranodal sinus with surrounding free spaces. Conversely, HRP 3 or higher, characterized by firm tumor cell adhesion to lymphoid tissue (HRP 3) or peritumoral desmoplastic reaction (HRP 4), independently impacted RFS, albeit not overall survival. Conclusions.— The prognosis of SBT with LNI is not uniformly favorable, and HRPs around the LNI significantly influence patient outcomes. Patients with firm tumor cell adhesion to surrounding tissue, with or without peritumoral desmoplastic reaction (HRP ≥3), independently experience decreased RFS, although this does not correlate with reduced overall survival.

Pathologist Concordance for Ovarian Carcinoma Subtype Classification and Identification of Relevant Histologic Features Using Microscope and Whole Slide Imaging

Context.— Despite several studies focusing on the validation of whole slide imaging (WSI) across organ systems or subspecialties, the use of WSI for specific primary diagnosis tasks has been underexamined. Objective.— To assess pathologist performance for the histologic subtyping of individual sections of ovarian carcinomas using a light microscope and WSI. Design.— A panel of 3 experienced gynecologic pathologists provided reference subtype diagnoses for 212 histologic sections from 109 ovarian carcinomas based on optical microscopy review. Two additional attending pathologists provided diagnoses and also identified the presence of a set of 8 histologic features important for ovarian tumor subtyping. Two experienced gynecologic pathologists and 2 fellows reviewed the corresponding WSI images for subtype classification and feature identification. Results.— Across pathologists specialized in gynecologic pathology, concordance with the reference diagnosis for the 5 major ovarian carcinoma subtypes was significantly higher for a pathologist reading on a microscope than each of 2 pathologists reading on WSI. Differences were primarily due to more frequent classification of mucinous carcinomas as endometrioid with WSI. Pathologists had generally low agreement in identifying histologic features important to ovarian tumor subtype classification with either an optical microscopy or WSI. This result suggests the need for refined histologic criteria for identifying such features. Interobserver agreement was particularly low for identifying intracytoplasmic mucin with WSI. Inconsistencies in evaluating nuclear atypia and mitoses with WSI were also observed. Conclusions.— Further research is needed to specify the reasons for these diagnostic challenges and to inform users and manufacturers of WSI technology.

Uncommon Cervical Lesions: A Review and Discussion of the Differential Diagnosis

Context.— While the vast majority of cervical tumors consist of human papillomavirus (HPV)–related squamous cell carcinoma or adenocarcinoma, a subset of rare tumor types, frequently unrelated to HPV, does occur in this location. These tumors vary widely in prognostic and therapeutic implications, and accurate recognition is crucial to providing appropriate treatment. Some are benign or portend a favorable prognosis (adenoid basal carcinoma, ectopic prostate tissue), while others are frankly malignant lesions with a less favorable prognosis (adenoid cystic carcinoma, HPV-negative endocervical adenocarcinoma, mesonephric adenocarcinoma, clear cell carcinoma, small cell carcinoma, and adenosquamous carcinoma). Objective.— To review the morphologic features of uncommon cervical lesions, the utility of immunohistochemistry for distinction between these entities, and the clinical and prognostic implications of accurate diagnosis. Data Sources.— University of Michigan cases and review of the pertinent literature regarding the entities described. Conclusions.— Key morphologic and immunohistochemical features detailed herein will allow for the accurate distinction between these uncommon cervical lesions. Morphology is most useful in discriminating between the entities, as there is frequent immunohistochemical overlap between them; however, in rare instances immunohistochemistry can be useful in resolving the diagnosis.

Practical Updates and Diagnostic Challenges in Endometrial Carcinoma

Context.— Clinical management of endometrial carcinoma largely depends on the morphologic parameters ascertained based on the pathologic evaluation of surgical resection specimens. However, there are numerous controversial and nonstandardized aspects of both the macroscopic and microscopic assessment of surgical specimens, including grossing, adequate sampling, diagnosis, staging, reporting, and ancillary testing. Objective.— To provide a comprehensive practical review of standardized grossing, key morphologic findings for reporting and staging, and diagnostic and prognostic use of ancillary testing in endometrial carcinomas. Data Sources.— The existing literature, recommendations of the International Society of Gynecological Pathologists, and specialty consensus guidelines. Conclusions.— This review article summarizes important aspects of the grossing and sampling of surgical resection specimens for microscopic examination, key morphologic parameters that are required for reporting and staging, and morphologic features and immunoprofiles helpful in the differential diagnosis of low-grade and high-grade endometrial carcinomas, as well as the current status of the molecular classification of endometrial carcinoma and human epidermal growth factor receptor 2 testing in serous carcinoma. The information presented herein can be helpful in overcoming diagnostic challenges and issues related to the pathology reporting of endometrial carcinoma to practicing anatomic pathologists.

The Rapidly Evolving Landscape of Human Epidermal Growth Factor Receptor 2 (HER2) Testing in Endometrial Carcinoma and Other Gynecologic Malignancies

Context.— Trastuzumab in combination with standard chemotherapy has been included in the guideline recommendations for human epidermal growth factor receptor 2 (HER2)–positive advanced-stage and recurrent endometrial carcinomas since 2019. A novel antibody drug conjugate, trastuzumab deruxtecan, gained tumor agnostic approval for HER2-positive metastatic solid tumors, including endometrial, ovarian, and cervical cancer, in 2024. Objective.— To provide a detailed overview of HER2 protein expression, gene amplification, and mutation in gynecologic malignancies in light of the newly available anti-HER2 therapies. Tumor-specific HER2 testing and scoring algorithms are discussed, including the implications of the DESTINY-PanTumor02 trial results and the significance of the HER2-low tumor category. Data Sources.— Review of the literature and personal experience of the author. Conclusions.— The clinical indications and demand for HER2 testing in gynecologic malignancies beyond endometrial cancer are expanding. It is essential for practicing pathologists to stay up to date on the latest clinical developments and use evidence-based HER2 testing and scoring criteria.

Ovarian Mucinous Neoplasms: An Integrated Clinicopathologic Perspective

Context.— Primary ovarian mucinous neoplasms represent a highly heterogeneous group of tumors. Despite being relatively common among ovarian tumors, they pose diagnostic challenges even for experienced gynecologic pathologists based on morphologic assessment, which serves as the primary means of classification and is intrinsically subject to substantial interobserver variability. Patients with low-stage disease generally have excellent outcomes, but infiltrative growth is associated with increased risk and high-stage disease is typically both aggressive and resistant to traditional therapy. Objective.— To review diagnostic criteria for classification of mucinous tumors, highlight recent updates on grading and ancillary testing, and discuss ongoing challenges of classification as they relate to clinical management. Data Sources.— Published peer-reviewed literature and personal experience of the authors. Conclusions.— Primary ovarian mucinous neoplasms are frequently encountered in routine gynecologic pathology practice; however, their classification remains problematic. Much of the difficulty surrounding their diagnosis stems from their incredible spatial heterogeneity, which is confounded by frequent discordance between gross and histologic findings. One is faced with an even greater challenge during intraoperative assessment, because it drastically alters surgical management in real time, with limited sampling. The recent adoption of growth pattern–based grading may ultimately serve as a means of simplifying the approach to these elusive tumors for patients who present with low-stage disease. For those presenting with high-stage disease, ancillary testing to guide individualized therapy remains largely rooted in pan-tumor strategies, and study of potential biomarker-based approaches is ongoing.

Evaluation of Laboratory-Derived Immunohistochemical Assays for Folate Receptor α Expression in Epithelial Ovarian Cancer and Comparison With a Companion Diagnostic

Context.— The VENTANA FOLR1 (FOLR1-2.1) RxDx (FOLR1 CDx) assay, developed by Roche Tissue Diagnostics, is a Food and Drug Administration–approved immunohistochemical assay intended for use in the assessment of folate receptor α (FRα) expression in formalin-fixed, paraffin-embedded epithelial ovarian, fallopian tube, and primary peritoneal tumor specimens. No published reports have compared the performance of other available FRα antibodies with the approved FOLR1 CDx. Objective.— To assess the performance of research FRα laboratory-developed tests compared with the FOLR1 CDx. Design.— The performance of 6 FRα-targeting antibodies was compared with the approved FOLR1 CDx in normal fallopian tube specimens. Two antibodies were selected for further assessment and compared with the FOLR1 CDx in ovarian tumor specimens. Results.— Of the 6 antibodies tested, 4 displayed a lack of specific membrane staining and/or high background, whereas 2 antibodies, produced by Leica Biosystems and Biocare Medical, respectively, exhibited specific and sensitive FRα staining. When assessed for their ability to correctly identify FRα-positive samples (per the FOLR1 CDx label, ≥75% of viable tumor cells with moderate and/or strong membranous staining intensity), both assays overpredicted FRα positivity compared with the FOLR1 CDx in archival ovarian tumor samples. Conclusions.— These data highlight the need for caution in antibody selection when developing immunohistochemistry-based assays, as some antibodies failed to cleanly and specifically identify FRα expression. We identified 2 antibodies appropriate for further investigation; however, as developed, these antibodies may overselect patients for treatment with FRα-targeted therapies.

Can Morphology and Immune Infiltration Predict the Homologous Recombination Deficiency Status in Newly Diagnosed High-Grade Serous Ovarian Carcinoma?: Lessons From the PAOLA-1/ENGOT-ov25 Trial, a GINECO Study

Context.— A correlation between the morphology of ovarian high-grade serous carcinomas (HGSOCs) and BRCA mutations has been previously reported. Objective.— To investigate, beyond BRCA , the association between the morphology of HGSOC and the presence of homologous recombination deficiency (HRD). Design.— We reviewed 522 of 806 cases of HGSOC from the PAOLA-1 clinical trial, including 163 cases with tumor BRCA mutation, 345 cases without tumor BRCA mutation, and 14 cases with inconclusive BRCA tests. Regarding HRD status (myChoice HRD Plus assay), 269 cases (52%) were positive (HRD + ), 198 (38%) negative (HRD − ), and 55 (10%) inconclusive. Morphologic analysis included tumor architecture (with more than 25% of solid, pseudoendometrioid, and transitional patterns defining a SET architecture), tumor-infiltrating intraepithelial lymphocytes (ieTILs), and tumor stromal lymphocytes (sTILs). Results.— SET architecture (51% versus 40%, P = .02), high number of ieTILs (16% versus 8%, P = .007), and more than 10% of sTILs (27% versus 18%, P = .02) were associated with tumor BRCA mutation, mostly for tumors with a BRCA1 mutation. These criteria were also associated with HRD status: 54% versus 33% ( P < .001) for SET architecture, 14% versus 6% ( P = .008) for high number of ieTILs, and 27% versus 15% ( P = .003) for more than 10% of sTILs. SET architecture was also significantly associated with HRD + tumors without tumor BRCA mutation ( P < .001) when compared with HRD − tumors. The combination of these 3 criteria showed high specificity (0.99; 95% CI, 0.97–0.99) but low sensitivity (0.07; 95% CI, 0.04–0.10). Conclusions.— The morphology of HGSOC correlates with HRD status and BRCA status but cannot substitute for molecular analysis in daily practice.

Intraplacental Gestational Neoplasms: A Review of Clinically Relevant Diagnostically Challenging Lesions

Context.— Case studies reporting intraplacental choriocarcinoma (IPC) and intraplacental “chorangiocarcinoma” have recently increased, with IPC also represented in molecular analyses of gestational trophoblastic neoplasms. Objective.— To provide an overview of 2 intraplacental neoplastic lesions that can have a significant impact on both mother and fetus/infant, focusing on diagnostic characteristics, and ancillary and molecular tools that support diagnosis, determine prognosis, and further elucidate the nature of these lesions. Data Sources.— Data were compiled from a PubMed literature review that included diagnostic and additional keywords within the scope of study for gestational choriocarcinoma in general. Illustrative cases were retrieved from the pathology archives at Michigan Medicine, including the consultation files of the author. Conclusions.— Intraplacental gestational tumors exist along the spectrum of benign (chorangioma) to aggressive malignant (choriocarcinoma) neoplasms with a high potential for metastasis. Although most gestational choriocarcinomas follow complete hydatidiform mole, 20% to 25% occur in association with normal intrauterine gestations, including rare cases in which they are detected within the placenta (IPC). IPCs range from asymptomatic to widely metastatic, with metastases possible even when only microscopic IPCs are present. A second, even less common lesion, variably called “chorangiocarcinoma” and chorangioma with atypical trophoblast proliferation, is also reviewed. The incidence of these lesions is likely to be underestimated. Heightened suspicion and more liberal placental sampling, particularly when specific clinical features are present, may result in higher detection. Enhanced detection to provide the earliest intervention for both mother and infant may improve prognosis, particularly for asymptomatic disease that may later present with metastasis.

Evaluation of Seegene Anyplex II Performance for Detection of Human Papillomavirus Genotypes in Formalin-Fixed, Paraffin-Embedded Cervical Cancer Specimens

Context.— Detection of human papillomavirus (HPV) in formalin-fixed, paraffin-embedded (FFPE) tissues may identify the cause of lesions and has value for the development of new diagnostic assays and epidemiologic studies. Seegene Anyplex II assays are widely used for HPV screening, but their performance using FFPE samples has not been fully explored. Objective.— To validate Anyplex II HPV HR Detection (Anyplex II, Seegene) using FFPE samples. Design.— We used 248 stored DNA extracts from cervical cancer FFPE samples collected during 2005–2015 that tested HPV positive using the RHA kit HPV SPF10-LiPA25, v1 (SPF10, Labo Biomedical Products) HPV genotyping assay, manufacturer-validated for FFPE samples. Results.— Of the selected 248 samples, 243 were used in our analysis. Consistent with SPF10 genotyping results, Anyplex II detected all 12 oncogenic types and had an overall HPV detection rate of 86.4% (210 of 243 samples). Anyplex II and SPF10 showed very high agreement for the detection of the 2 most important oncogenic genotypes: HPV 16 (219 of 226; 96.9%; 95% CI, 93.7–98.75) and HPV 18 (221 of 226; 97.8%; 95% CI, 94.9–99.3). Conclusions.— Overall results showed that both platforms produced comparable HPV genotyping results, indicating the suitability of Anyplex II for FFPE samples. The Anyplex II assay has the added convenience of being an efficient, single-well semiquantitative polymerase chain reaction assay. Further optimization of Anyplex II may enhance its performance using FFPE samples by improving the detection limit.

Synchronous Epidermodysplasia Verruciformis and Intraepithelial Lesion of the Vulva Is Caused by Coinfection With Alpha-Human Papillomavirus and Beta-Human Papillomavirus Genotypes and Facilitated by Mutations in Cell-Mediated Immunity Genes

Context.— There have been exceedingly few reports of epidermodysplasia verruciformis (EV) or EV-like lesions in the vulva. We describe the first observation of vulvar lesions displaying synchronous EV-like histology and conventional high-grade squamous intraepithelial lesion (HSIL), a finding hitherto unreported in medical literature. Objectives.— To describe this novel vulvar lesion with hybrid features of HSIL and EV, attempt to confirm the hypothesis of coinfection with α and β human papillomavirus (α-HPV and β-HPV) genotypes, and describe relevant underlying genetic mutations. Design.— Cases were retrospectively selected from our institutional archive. Detailed review of clinical information, histologic examination, and whole genome sequencing (WGS) were performed. Results.— Five samples from 4 different patients were included. Three of 4 patients had a history of either iatrogenic immune suppression or prior immune deficiency, and all 3 featured classic HSIL and EV changes within the same lesion. One patient had no history of immune disorders, presented with EV-like changes and multinucleated atypia of the vulva, and was the sole patient without conventional HSIL. By WGS, several uniquely mappable reads pointed toward infection with multiple HPV genotypes, including both α-HPVs and β-HPVs. Mutations in genes implicated in cell-mediated immunity, such as DOCK8, CARMIL2, MST1, and others, were also found. Conclusions.— We provide the first description of vulvar lesions harboring simultaneous HSIL and EV features in the English-language literature, a phenomenon explained by coinfection with α-HPV and β-HPV genotypes. The finding of EV-like changes in a vulvar specimen should prompt assessment of the patient’s immune status.

Peripheral Blood Plasminogen Activator Inhibitor 1 and Tissue-Type Plasminogen Activator-Inhibitor Complex Levels for the Diagnosis and Prediction Value of Venous Thromboembolism in Malignant Tumors

Context.— Patients with malignant tumors complicated by venous thromboembolism (VTE) face high mortality rates because of a lack of effective diagnostic and predictive markers. Plasminogen activator inhibitor 1 (PAI-1) and tissue-type plasminogen activator-inhibitor complex (t-PAIC) may contribute to VTE formation in these patients. Objective.— To evaluate the diagnostic and predictive value of peripheral blood PAI-1 and t-PAIC levels in patients with malignant tumors complicated by VTE and to develop a new thrombosis risk score model (NRS) based on PAI-1 levels. Design.— This study included 216 patients with malignant tumors (lung, colorectal, ovarian, breast, and gastric cancers). The correlation between PAI-1 and t-PAIC levels was explored. The predictive value of PAI-1 and t-PAIC, combined with the COMPASS-CAT risk score, Khorana risk score, and Padua risk score, was assessed for postoperative VTE risk. Differences in PAI-1 and t-PAIC levels across tumor types were also analyzed. Results.— The PAI-1 and t-PAIC levels were positively correlated. Preintervention PAI-1 levels independently predicted VTE risk, and the new thrombosis risk score model could effectively predict the occurrence of concurrent VTE in patients with malignancy. PAI-1 and t-PAIC have better diagnostic value for VTE than D-dimers. Combining these markers with the COMPASS-CAT risk score, Khorana risk score, and Padua risk score improves the risk prediction of VTE. PAI-1 levels were significantly associated with VTE risk in colorectal cancer, whereas t-PAIC levels were significantly associated with VTE risk in breast cancer. Conclusions.— Peripheral blood PAI-1 and t-PAIC levels have excellent predictive and diagnostic value for VTE in patients with malignancy.

Endometriosis-Associated Neoplasms: A Review of Clinicopathologic Features and Common Diagnostic Challenges

Context.— Neoplastic potential of endometriosis is well established, albeit rare, and endometriosis-associated neoplasms are frequently encountered in clinical practice. Objective.— To summarize and review common diagnostic issues with endometriosis and endometriosis-associated neoplasms, as well as review clinical, pathologic, and molecular characteristics of these tumors and discuss differential diagnoses. Data Sources.— Literature review and cases from the authors’ personal practice. Conclusions.— Endometriosis-associated neoplasms are a frequently encountered heterogeneous group of ovarian neoplasms with some unifying features, including younger age and lower stage at presentation. The most common tumors are endometrioid carcinomas, clear cell carcinomas, and seromucinous borderline tumors. The diverse morphologic features and variant histologic patterns can significantly complicate interpretation and compromise reproducibility. This review offers a systematic approach in overcoming these diagnostic challenges that are facilitated by the integration of histologic, immunohistochemical, and molecular findings.

Steroidogenic Acute Regulatory Protein Is a Useful Marker for Sex-Cord-Stroma Tumors and Normal and Neoplastic Adrenocortical Tissue

Context.— Steroidogenic acute regulatory (StAR) protein is a mitochondrial transport protein with a critical regulatory role for steroid hormone production. The tissue distribution of StAR expression is limited to few human normal tissues. Objective.— To assess the diagnostic and prognostic value of StAR immunohistochemistry analysis. Design.— A tissue microarray containing 19 202 samples from 152 different tumor types and subtypes and 608 samples of 76 different normal tissue types was analyzed by immunohistochemistry. Result.— StAR immunostaining occurred in 198 (1.2%) of the 17 135 analyzable tumors. StAR expression was observed in 27 of 152 tumor categories, 9 of which included at least 1 strongly positive case. The highest rate of StAR positivity occurred in Leydig cell tumors of the testis and the ovary (100%), steroid cell tumors of the ovary (100%), adrenocortical carcinomas (93%) and adenomas (87%), Sertoli-Leydig cell tumors (67%) and granulosa cell tumors of the ovary (56%), as well as seminomas (7%). Nineteen other tumor entities showed—a usually weak—StAR positivity in less than 6% of cases. A comparison with preexisting Melan-A (a melanocyte antigen) data revealed that StAR was more often positive in adrenocortical neoplasms and in Leydig cell tumors while StAR (but not Melan-A) was negative in Sertoli cell tumors. Conclusions.— Our data provide a comprehensive overview on the patterns of StAR immunostaining in human tumors and suggest a diagnostic utility of StAR immunohistochemistry for supporting a diagnosis of Leydig cell tumors or of normal or neoplastic adrenocortical tissue.

Creation of a Quality Payment Program Measure for Mismatch Repair or Microsatellite Instability Biomarker Testing Status in Colorectal, Endometrial, Gastroesophageal, or Small Bowel Carcinoma

Context.— Quality measures that are supported by evidence-based clinical practice guidelines are preferred for assessing the quality of pathologists' practices. Careful testing of a measure ensures that scores obtained by that measure reflect the quality of a pathologist's practice. Objective.— To specify a new quality measure and to demonstrate through testing that it is suitable for measuring pathologists' appropriate incorporation of information regarding microsatellite instability (MSI) and/or mismatch repair (MMR) status in pathology reports for colorectal, endometrial, gastroesophageal, and small bowel carcinoma. Design.— The College of American Pathologists collaborated with the American Gastroenterological Association to specify and test the new measure. Face validity testing was used to investigate the validity of the measure. Feasibility testing was conducted to understand if data elements required by the measure specification were readily accessible. Signal-to-noise analysis was used to characterize the measure's reliability. Results.— Guideline recommendations for MSI and/or MMR testing supported specifications for the measure. Face validity testing indicated that the measure could distinguish the quality of care provided. Data elements required by the measure specification were found to be accessible, which supported the measure's feasibility. Reliability testing showed that differences in measure score were attributable to real differences in performance rather than random variation in scoring. Conclusions.— The Mismatch Repair or Microsatellite Instability Biomarker Testing Status in Colorectal Carcinoma, Endometrial, Gastroesophageal, or Small Bowel Carcinoma measure was appropriately specified, and testing demonstrated that it is well suited for characterizing the quality of pathologists' communication of MMR and/or MSI status.

A Timely Update of Immunohistochemistry and Molecular Classification in the Diagnosis and Risk Assessment of Endometrial Carcinomas

Context.— Endometrial carcinoma is the most common gynecologic malignancy in the United States and has been traditionally classified based on histology. However, the distinction of certain histologic subtypes based on morphology is not uncommonly problematic, and as such, immunohistochemical study is often needed. Advances in comprehensive tumor sequencing have provided novel molecular profiles of endometrial carcinomas. Four distinct molecular subtypes with different prognostic values have been proposed by The Cancer Genome Atlas program: polymerase epsilon ultramutated, microsatellite instability hypermutated, copy number low (microsatellite stable or no specific molecular profile), and copy number high (serouslike, p53 mutant). Objective.— To discuss the utilities of commonly used immunohistochemical markers for the classification of endometrial carcinomas and to review the recent advancements of The Cancer Genome Atlas molecular reclassification and their potential impact on treatment strategies. Data Sources.— Literature review and authors' personal practice experience. Conclusions.— The current practice of classifying endometrial cancers is predominantly based on morphology. The use of ancillary testing, including immunohistochemistry, is helpful in the identification, differential diagnosis, and classification of these cancers. New developments such as molecular subtyping have provided insightful prognostic values for endometrial carcinomas. The proposed The Cancer Genome Atlas classification is poised to gain further prominence in guiding the prognostic evaluation for tailored treatment strategies in the near future.

Effectiveness of Human Papillomavirus Self-collection for Cervical Cancer Screening in Community Outreach Programs

Context.— On May 14, 2024, the US Food and Drug Administration (FDA) approved self-collected vaginal samples for human papillomavirus (HPV) testing, expanding cervical cancer screening access. Objective.— To evaluate the feasibility and acceptability of HPV self-collection through community outreach programs targeting underscreened populations in Oregon. Design.— From October 2024 to June 2025, women aged 25 to 65 years were recruited through local organizations. Following instruction by pathologists, participants completed self-collection by using Copan swabs, which were transferred to ThinPrep media for high-risk HPV testing using the Cobas 8800 system. Postcollection surveys assessed user experience. Results.— Among 156 participants (mean age, 47.1 years), 87 (55.8%) identified as Hispanic and 69 (44.2%) as non-Hispanic. Racial groups included Hispanic White (87; 55.8%), Asian (33; 21.1%), Black (16; 10.3%), non-Hispanic White (14; 9.0%), Pacific Islander (2; 1.3%), and nondisclosed (4; 2.5%). All tests were valid; 10 participants (6.4%) were HPV-positive, including 1 with HPV-18 and 9 with non-16/18 types. Follow-up cytology showed 1 case of atypical squamous cells of undetermined significance and 2 negative results; the remainder are pending follow-up. Of 129 survey respondents, 8 (6.2%) had received the HPV vaccine. Overall, 117 (90.7%) found the self-collection kit easy to use, 114 (88.4%) would recommend it, and 91 (70.6%) were likely to choose self-collection over clinician-collected samples for future testing. Common feedback included convenience, comfort, and privacy. Conclusions.— HPV self-collection is a practical, user-friendly, and accessible screening option. Pathologist-led outreach may help close screening gaps. This study represents the first academic center-led implementation of FDA-approved self-collection in US community settings.

Rescreening Practices of Negative Papanicolaou Tests With Positive Human Papillomavirus Test Result

Context.— The yield of the prospective rescreening process for “negative for intraepithelial lesion or malignancy” (NILM) Papanicolaou (Pap) tests is higher with the inclusion of a greater proportion of high-risk cases. One of the suggested criteria for classifying a Pap test finding as high risk is recent or concurrent high-risk human papillomavirus (HPV) positivity. Objective.— To evaluate how the results of HPV testing have been incorporated in the prospective rescreening of NILM Pap tests across a wide range of laboratories. Design.— A questionnaire survey was sent to laboratories participating in the 2019 College of American Pathologists (CAP) Gynecologic Cytology (PAP Education) Program. Results.— Of the 1507 participating laboratories, 667 (44%) responded to the survey. Most laboratories (59.4%; 396 of 667) had not incorporated HPV test/genotyping results to select NILM Pap tests for rescreening. Amongst the remaining laboratories, for NILM HPV-positive Pap test results, 112 (16.8%) had a policy to rescreen by a cytotechnologist only, 51 (7.6%) by a pathologist only, and 86 (12.9%) by both. Of 264 laboratories, 181 (68.6%) reported the cytology upon availability of the HPV test result and completion of the secondary review. Of 661 laboratories, 145 (21.9%) included consensus-type recommendations in the cytology report for such Pap tests. Conclusions.— This CAP survey provides significant information regarding the current trends in the use of HPV test results in prospective rescreening of NILM Pap tests. Future studies on quality improvement can further assist in the standardization of this process across different laboratories.

Epidemiology Characteristics and Potential Cervical Cancer Screening Value of Vulvar Human Papillomavirus in Chinese Women: A Multicenter Cross-Sectional Study

Context.— Noninvasive self-sampling is a convenient option that may be highly accepted by women for home-based detection, which could increase the screening rate for cervical cancer (CC) and reduce its incidence and mortality. Objective.— To compare the distribution of high-risk human papillomavirus (hr-HPV) between the vulva and cervix and to explore the clinical value of vulvar HPV detection in CC screening. Design.— The study was nested within a clinical trial on a recombinant HPV 9–valent vaccine for women ages 20 to 45 years. Women with paired vulvar and cervical specimens were included and underwent cytology and HPV detection. The consistency of HPV detection between vulvar and cervical specimens was evaluated using Cohen κ statistics. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were used to evaluate the diagnostic accuracy of primary CC screening. The primary end points were cervical intraepithelial neoplasia (CIN) grade 2/3 or worse (CIN2+/3+). Results.— A total of 7999 women were enrolled, and 83/33 cases were diagnosed as CIN2+/CIN3+. The HPV-positive rate in vulvar specimens (1785 of 7999; 22.32%) was higher than that in cervical specimens (1390 of 7999; 17.38%), and there were no significant differences in the distribution of hr-HPV genotypes between the vulva and cervix in patients with CIN2+/CIN3+. Vulva-based HPV primary screening showed sensitivity, specificity, PPV, and NPV comparable to those for cervix-based HPV primary CC screening in the detection of CIN3+. Conclusions.— The distribution of vulvar and cervical HPV was similar in patients with CIN2+/CIN3+. Vulva-based HPV primary CC screening had acceptable diagnostic efficacy and might be used as a modality for primary CC screening.

Navigating Practice Issues Related to the Unsatisfactory Cervicovaginal Papanicolaou Test: Survey Results of Laboratories Participating in the 2020 College of American Pathologists PAP Education Program

Context.— Unsatisfactory Papanicolaou (Pap) tests pose a unique set of challenges to the laboratory with regard to their processing, review, reporting, and performance of human papillomavirus (HPV) testing. There are no standardized guidelines for the review process and handling of unsatisfactory Pap tests. Objective.— To assess the current practice patterns regarding various aspects of the unsatisfactory Pap test, from processing to reporting, across laboratories worldwide. Design.— A supplemental questionnaire was mailed to laboratories participating in the 2020 College of American Pathologists (CAP) Gynecologic Cytopathology (PAP Education) Program, requesting data regarding the unsatisfactory Pap test. Results.— Of 1520 participating laboratories, 619 (40.7%) responded, and the responses of 577 laboratories were included for further analysis. Only 64.6% (373 of 577) laboratories used the unsatisfactory Pap test criteria as specified by the 2014 Bethesda System. About three-quarters of the respondents (433 of 576; 75.2%) routinely rescreened unsatisfactory Pap tests. Routine repreparation of such Pap tests was performed by 54.9% (316 of 576) of laboratories, and 52.0% (293 of 563) used glacial acetic acid for repreparing excessively bloody specimens. HPV test results were reported for unsatisfactory Pap tests, always or sometimes, by 62.4% (353 of 566) of respondents. Conclusions.— This CAP survey reveals important information regarding the practice patterns pertaining to several aspects of the unsatisfactory Pap test. It also provides valuable insight into the quality assurance measures that can be implemented for such tests. Future studies can further aid in the standardization of all components of the handling of unsatisfactory Pap tests for overall quality improvement.

The Differential Diagnosis of Reparative Changes and Malignancy: Performance in the College of American Pathologists Pap Education and Proficiency Testing Programs

Context.— Repair is a challenging diagnosis and a significant source of false-positive (FP) interpretations in cervical cytology. No large-scale study of performance of repair in the liquid-based era has been performed. Objective.— To evaluate the performance of repair in the College of American Pathologists Pap Education and Proficiency Testing (PT) programs. Design.— The FP rate for slides classified as repair was evaluated by preparation type, participant type (cytotechnologist, pathologist, or laboratory), and program. The specific misdiagnosis category and individual slide performance were also evaluated. The rate of misclassification of slides as repair by participants for other diagnostic categories in the Pap Education program was assessed. Results.— The overall FP rate was 1700 of 12 715 (13.4%). There was no significant difference by program or preparation type. Within the Education program there was no difference by participant type, but pathologists' FP rate in the PT program (47 of 514, 9.1%) was significantly better than cytotechnologists in the PT program (51 of 380, 13.4%) and pathologists in the Education program (690 of 4900, 14.1%). High-grade squamous intraepithelial lesions/cancers (HSIL+) accounted for 1380 of 1602 FP interpretations (86%) in Education, but 43 of 98 (43.9%) in PT. Most slides had a low rate of misclassification, but a small number were poor performers. False-negative diagnosis of HSIL+ as repair was less common, ranging from 0.7% to 1.8%. Conclusions.— Despite initial indications that liquid-based cytology might reduce the rate of misclassification of repair, FP interpretations remain common and are no different by preparation type. Misclassification is most commonly as HSIL or carcinoma, potentially resulting in significant patient harm.

Cystic Granulosa Cell Tumors of the Ovary: An Analysis of 80 Cases of an Often Diagnostically Challenging Entity

Context.— Granulosa cell tumors (GCTs) of both adult (AGCT) and juvenile (JGCT) types can rarely be completely or dominantly cystic, creating diagnostic difficulty because the cyst lining epithelium is often denuded. Objective.— To describe clinical, gross, microscopic, immunohistochemical, and molecular features of cystic GCTs with an emphasis on their differential diagnosis. Design.— We report 80 cystic GCTs (24 AGCTs and 56 JGCTs) in patients from ages 3 to 83 years (average ages, 35 years for AGCT and 22 years for JGCT). Results.— Nineteen of 43 patients with known clinical information (3 AGCT and 16 JGCT) had androgenic manifestations. All tumors were greater than 8 cm (average, 17 cm) with minimal to absent gross solid component. Denudation of cells lining the cysts was prominent. Invagination of the epithelium into the cyst walls was a key diagnostic feature, was present as cords, trabeculae, solid nests, and small and large follicles, and was identified in most tumors (17 AGCTs and 45 JGCTs). Cytologic atypia was essentially absent in AGCTs, whereas 14 JGCTs showed moderate to severe atypia of bizarre type. A theca cell component was present in all tumors and was extensive in 54. A FOXL2 hotspot mutation was identified in 1 of 4 AGCTs tested. Conclusions.— Despite extensive denudation, the finding of typical architectural patterns and cytologic features as well as, in some cases, androgenic manifestations helps differentiate cystic GCTs from follicle cysts, the most common and challenging differential diagnosis, as well as other cystic neoplasms that may enter the differential diagnosis. FOXL2 sequencing may show a false-negative result in cystic AGCT because of the limited number of cells present within the tumor sample.

Reporting Results of Biomarker Testing of Specimens From Patients With Carcinoma of Gynecologic Origin: The Updated College of American Pathologists Protocol

Context.— The first version of the Template for Reporting Results of Biomarker Testing of Specimens From Patients With Carcinoma of Gynecologic Origin (hereafter referred to as the Gynecologic Biomarker Protocol) was released by the College of American Pathologists (CAP) in 2022. Minor updates included clarification of the content of p53 status and explanatory notes for human epidermal growth factor receptor 2 (HER2) and mismatch repair testing in 2023. Recent developments in biomarker testing have prompted a major update to this protocol, published in December 2024. Objective.— To assess prognostic and/or therapeutic markers since the release of the 2023 Gynecologic Biomarker Protocol and to update testing recommendations in gynecologic carcinomas, with expanded explanatory notes and illustrative examples provided in this article. Design.— The CAP Cancer Committee assembled a panel of experts subspecialized in gynecologic pathology to augment the existing biomarkers, add new biomarkers, expand test reporting, and revise explanatory notes based on available evidence and clinical practice guidelines such as those of the American Society of Clinical Oncology/CAP, National Comprehensive Cancer Network, and Society for Immunotherapy of Cancer. Results.— The changes to the Gynecologic Biomarker Protocol include updates to hormone receptors and addition of subclonal loss of mismatch repair proteins, subclonal abnormal p53 expression, programmed death ligand-1 (PD-L1) testing, and folate receptor alpha testing, as well as updates to HER2 testing and all explanatory notes. Conclusions.— The updated CAP Gynecologic Biomarker Protocol provides improved structure and clarity in the reporting of prognostic and/or therapeutic biomarkers and comprehensive explanatory notes that aid in understanding the rationale for testing, interpretive guidance, and common testing pitfalls, based on the current standard of care.

Relationships of p16 Immunohistochemistry and Other Biomarkers With Diagnoses of Cervical Abnormalities: Implications for LAST Terminology

Context.— Lower Anogenital Squamous Terminology (LAST) standardization recommended p16INK4a immunohistochemistry (p16 IHC) for biopsies diagnosed morphologically as cervical intraepithelial neoplasia (CIN) grade 2 (CIN2) to classify them as low-grade or high-grade squamous intraepithelial lesions (HSILs). Objective.— To describe the relationships of p16 IHC and other biomarkers associated with cervical cancer risk with biopsy diagnoses. Design.— A statewide, stratified sample of cervical biopsies diagnosed by community pathologists (CPs), including 1512 CIN2, underwent a consensus, expert pathologist panel (EP) review (without p16 IHC results), p16 IHC interpretation by a third pathology group, and human papillomavirus (HPV) genotyping, results of which were grouped hierarchically according to cancer risk. Antecedent cytologic interpretations were also available. Results.— Biopsies were more likely to test p16 IHC positive with increasing severity of CP diagnoses, overall (Ptrend ≤ .001) and within each HPV risk group (Ptrend ≤ .001 except for low-risk HPV [Ptrend < .010]). All abnormal grades of CP-diagnosed biopsies were more likely to test p16 IHC positive with a higher HPV risk group (Ptrend < .001), and testing p16 IHC positive was associated with higher HPV risk group than testing p16 IHC negative for each grade of CP-diagnosed biopsies (P < .001). p16 IHC–positive, CP-diagnosed CIN2 biopsies were less likely than CP-diagnosed CIN3 biopsies to test HPV16 positive, have an antecedent HSIL+ cytology, or to be diagnosed as CIN3+ by the EP (P < .001 for all). p16 IHC–positive, CP-diagnosed CIN1 biopsies had lower HPV risk groups than p16 IHC–negative, CP-diagnosed CIN2 biopsies (P < .001). Conclusions.— p16 IHC–positive, CP-diagnosed CIN2 appears to be lower cancer risk than CP-diagnosed CIN3. LAST classification of “HSIL” diagnosis, which includes p16 IHC–positive CIN2, should annotate the morphologic diagnosis (CIN2 or CIN3) to inform all management decisions, which is especially important for young (<30 years) women diagnosed with CIN2 for whom surveillance rather than treatment is recommended.

Interobserver Agreement Across Subspecialties for Diagnosis of Differentiated Vulvar Intraepithelial Neoplasia and Predictive Values of 20 Histologic Features

Context.— Differentiated vulvar intraepithelial neoplasia (dVIN) is a human papillomavirus–independent lesion with the potential for rapid progression to invasive squamous cell carcinoma (SCC). The histopathologic features of dVIN are diverse, have overlapping characteristics with lichen sclerosus (LS) and lichen simplex chronicus (LSC), and may be diagnosed by dermatopathologists or gynecologic pathologists because of the vulva’s anatomic location. Objectives.— To identify the salient histopathologic features of dVIN, particularly those that predict progression to SCC, and to evaluate interobserver agreement in diagnosing dVIN within the same subspecialty and across subspecialties. Design.— One general surgical pathologist, 2 pathology-trained dermatopathologists, and 1 gynecologic pathologist blinded to the final diagnoses were asked to record 20 histopathologic features and to provide their final interpretations on cases of dVIN (n = 65), LS (n = 126), LSC (n = 112), and LS with LSC (n = 6). Results.— Interobserver agreement for the 4 diagnoses and 10 histopathologic features was moderate. Logistic regression analysis indicated that keratin pearls, basal pleomorphism, and basal layer disarray were independent variables for diagnosing dVIN (coefficients 1.95, 1.97, and 0.91, respectively; P < .001) and progression to SCC (coefficients 1.96, 1.20, and 1.08, respectively; P < .001). Conclusions.— There is no single histopathologic feature pathognomonic for dVIN; however, the presence of keratin pearls, basal pleomorphism, and basal layer disarray should raise high suspicion for dVIN and concurrent SCC. Expertise in both dermatologic and gynecologic pathology is beneficial for diagnosing dVIN.

Frequent Immunohistochemical Expression of Transcriptional Repressor GATA Binding 1 in Salivary Gland Neoplasms: A Sensitive but Nonspecific Marker

Context.— Salivary gland (SG) neoplasms (SGNs) display considerable immunophenotypic diversity. A significant proportion of SG carcinomas develop metastases, with increased diagnostic difficulty at metastatic sites. Transcriptional repressor GATA binding 1 (TRPS1), a novel immunohistochemical marker for breast cancer, has been found to stain certain SGNs. Objective.— To investigate TRPS1 and SRY-related HMG-box 10 (SOX10) immunoexpression in various SGNs and non-SG carcinomas, head and neck paragangliomas, and head and neck mucosal melanomas. Design.— TRPS1 immunoreactivity score (IRS) was determined as negative or low, intermediate, or high positive; SOX10 was reported as negative or positive. Results.— One hundred forty-eight SGNs, 5 breast carcinomas, 105 nonbreast–non-SG carcinomas, including 33 head and neck squamous cell carcinomas (HNSCCs), 6 head and neck paragangliomas, and 6 head and neck mucosal melanomas, were assessed for TRPS1. All 23 benign SGNs showed TRPS1 positivity, with the majority having high-positive IRS (17 of 23 cases; 74%). Among 125 SG carcinomas, 115 of 125 (92%) were TRPS1 positive, with high-positive IRS in 94 of 125 (75%), intermediate-positive IRS in 15 of 125 (12%), and low-positive IRS in 6 of 125 (5%). Among nonbreast–non-SG carcinomas, HNSCC, lung, thyroid, kidney, and ovarian carcinomas showed frequent TRPS1 staining. Nearly half of HNSCCs had high (11 of 18; 33%) or intermediate (4 of 18; 12%) positive IRS. Mean IRS in SG carcinomas was significantly higher than that in nonbreast–non-SG carcinomas (P < .001). None of the TRPS1-positive nonbreast–non-SG carcinomas expressed SOX10. Conclusions.— TRPS1 is positive in most benign and malignant SGNs. Its expression in several nonbreast–non-SG carcinomas indicates that it lacks specificity for breast and SG carcinomas, even if considering only high-positive IRS. Addition of SOX10 can increase the discriminatory utility of TRPS1.

Adenocarcinomas of the Gynecologic Tract Involving the Urinary Bladder: A Series of 16 Cases Potentially Mimicking Urothelial Malignancy

Context.— There is limited literature describing gynecologic adenocarcinomas involving the urinary bladder and potential diagnostic pitfalls. Objective.— To describe key features distinguishing metastatic (or extension of) gynecologic adenocarcinomas from urothelial carcinomas with glandular differentiation. Design.— Retrospective review of surgical pathology cases of gynecologic adenocarcinomas involving the bladder from 2 different institutions, retrieved from surgical pathology archives, was performed. Morphologic features were recorded, along with immunohistochemistry results when available. Electronic medical records were reviewed for clinical and radiographic information. Results.— Sixteen cases of gynecologic adenocarcinomas (9 endometrial endometrioid adenocarcinomas, 4 endometrial serous carcinomas, 2 high-grade tubo-ovarian serous carcinomas, and 1 cervical adenosquamous carcinoma) involving the bladder were identified. All included cases had mucosal involvement potentially mimicking primary bladder neoplasms, including 4 cases originally diagnosed as urinary carcinomas. Tumors expressed keratin 7 (12 of 13; 92%), PAX8 (11 of 12; 92%), estrogen receptor (11 of 15; 73%), p16 (8 of 11; 73%), progesterone receptor (8 of 14; 57%), GATA3 (5 of 12; 42%), and p63 (3 of 11; 27%); all tumors were negative for keratin 20 (0 of 12). Features supportive of Müllerian origin included prior history of gynecologic malignancy, lack of morphologic heterogeneity in nonendometrioid tumors, and immunophenotypic coexpression of PAX8 and estrogen receptor with absent GATA3. Potential pitfalls seen in a subset of cases included misleading radiologic and cystoscopic findings, replacement of the overlying urothelial mucosa by tumor mimicking precursor lesions, focal GATA3 and/or p63 positivity, and areas of squamous differentiation in tumors of endometrioid histology. Conclusions.— A combination of clinical history, certain morphologic features, and proper selection of immunohistochemical stains is key for the correct diagnosis of secondary gynecologic adenocarcinomas involving the urinary bladder.

The Spectrum of Fusions Occurring in Non–Smooth Muscle Mesenchymal Uterine Tumors: A Review of the Current Knowledge

Context.— Non–smooth muscle uterine sarcomas are mostly represented by low-grade endometrial stromal sarcoma. However, several other rare, distinct types of uterine sarcoma are recognized, including high-grade endometrial stromal sarcoma, tumors with kinase fusions, uterine tumors resembling ovarian sex cord tumors, soft tissue–type sarcoma, and emerging entities such as KAT6A/B-rearranged tumors. The landscape of uterine sarcomas has changed, mostly because of the increasing knowledge concerning their molecular aberrations. Objective.— To offer a comprehensive review of the literature focusing on fusions occurring in tumors other than smooth muscle mesenchymal uterine tumors with respect to their type, frequency, and overlap between diagnostic categories and entities. Data Sources.— The data were mined from the PubMed/MEDLINE database covering the time period from January 1988 to June 2023. In total, 156 studies focusing on the problematics of fusions occurring in non–smooth muscle mesenchymal uterine tumors were selected, and thus became the basis for this review. Conclusions.— One hundred ten fusions were identified in 703 tumors. The diagnostic significance of the molecular aberrations occurring in these tumors can be unclear in some cases. This can be related to the rare aberrations with a limited number of reported cases. Additionally, even well-known aberrations considered as specific for a certain distinct entity can occur in other lesions, the biological behavior and clinical significance of which can differ substantially.

Neoplastic Progression in Macroscopic Precursor Lesions of the Pancreas

Context.— Macroscopic precursor lesions of the pancreas represent a complex clinical management problem. Molecular characterization of pancreatic cysts has helped to confirm and refine clinical and pathologic classifications of these lesions, inform our understanding of tumorigenesis in the pancreas, and provide opportunities for preoperative diagnosis. Objective.— To review the pathologic classification of macroscopic cystic lesions of the pancreas: intraductal papillary mucinous neoplasms (IPMNs), mucinous cystic neoplasms (MCNs), intraductal oncocytic papillary neoplasms (IOPNs), and intraductal tubulopapillary neoplasms (ITPNs), and to describe our current state of understanding of their molecular underpinnings, relationship to invasive carcinomas, and implications for diagnosis and prognostication. Data Sources.— We assessed the current primary literature and current World Health Organization Classification of Digestive System Tumours. Conclusions.— Macroscopic cystic lesions of the pancreas are morphologically and molecularly diverse. IPMNs and MCNs share mucinous cytoplasm with papillae. MCNs are defined by ovarian-type stroma. IOPNs have granular eosinophilic cytoplasm, prominent nucleoli, and complex, arborizing papillae. ITPNs demonstrate complex, back-to-back tubules and anastomosing papillae and lack prominent intracellular mucin. IPMNs and MCNs are characterized by driver mutations in KRAS/GNAS (IPMNs) and KRAS (MCNs), with later driver events in RNF43, CDKN2A, SMAD4, and TP53. In contrast, IOPNs and ITPNs have recurrent rearrangements in PRKACA/PRKACB and MAPK-associated genes, respectively. The recurrent alterations described in cysts provide an opportunity for diagnosis using aspirated cyst fluid. Molecular characterization of IPMNs shows a striking spatial and mutational heterogeneity, challenging traditional models of neoplastic development and creating challenges to interpretation of cyst fluid sequencing results.

Development of an FRα Companion Diagnostic Immunohistochemical Assay for Mirvetuximab Soravtansine

Context.— Folate receptor-α (FRα, encoded by the FOLR1 gene) is overexpressed in several solid tumor types, including epithelial ovarian cancer (EOC), making it an attractive biomarker and target for FRα-based therapy in ovarian cancer. Objective.— To describe the development, analytic verification, and clinical performance of the VENTANA FOLR1 Assay (Ventana Medical Systems Inc) in EOC. Design.— We used industry standard studies to establish the analytic verification of the VENTANA FOLR1 Assay. Furthermore, the VENTANA FOLR1 Assay was used in the ImmunoGen Inc–sponsored SORAYA study to select patients for treatment with mirvetuximab soravtansine (MIRV) in platinum-resistant EOC. Results.— The VENTANA FOLR1 Assay is highly reproducible, demonstrated by a greater than 98% overall percent agreement (OPA) for repeatability and intermediate precision studies, greater than 93% OPA for interreader and greater than 96% for intrareader studies, and greater than 90% OPA across all observations in the interlaboratory reproducibility study. The performance of the VENTANA FOLR1 Assay in the SORAYA study was evaluated by the overall staining acceptability rate, which was calculated using the number of patient specimens that were tested with the VENTANA FOLR1 Assay that had an evaluable result. In the SORAYA trial, data in patients who received MIRV demonstrated clinically meaningful efficacy, and the overall staining acceptability rate of the assay was 98.4%, demonstrating that the VENTANA FOLR1 Assay is safe and effective for selecting patients who may benefit from MIRV. Together, these data showed that the assay is highly reliable, consistently producing evaluable results in the clinical setting. Conclusions.— The VENTANA FOLR1 Assay is a robust and reproducible assay for detecting FRα expression and identifying a patient population that derived clinically meaningful benefit from MIRV in the SORAYA study.

B7-H4 Further Stratifies Patients With Endometrial Cancer Exhibiting a Nonspecific Molecular Profile

Context.— Endometrial cancer is classified into 4 molecular subtypes: DNA polymerase epsilon ultramutated, mismatch repair deficient, p53 mutant, and nonspecific molecular profile (NSMP). Additional biomarkers are urgently needed to better characterize the NSMP subtype, the largest group with heterogeneous pathologic features and prognoses. Objective.— To investigate the expression of B7 homolog 3 (B7-H3), B7 homolog 4 (B7-H4), and V-set and immunoglobulin domain containing 3 (VSIG-3, a ligand for B7-H5) in 833 patients with endometrial cancer and determine their associations with clinicopathologic and molecular features as well as survival outcomes. Design.— Molecular classification was determined by polymerase epsilon sequencing and immunohistochemical staining for p53 and mismatch repair proteins. B7-H3, B7-H4, VSIG-3, and programmed death ligand-1 (PD-L1) were detected via immunohistochemistry. Results.— The positivity rates for B7-H3 in each of the tumor and immune cells, B7-H4 (exclusively in tumor cells), and VSIG-3 (exclusively in tumor cells) were 89.0%, 42.3%, 71.5%, and 99.8%, respectively. B7-H3 and B7-H4 positivity in tumor cells was associated with favorable pathologic features and prognosis. In contrast, B7-H3 expression in immune cells was frequent in samples with unfavorable pathologic features; those with p53-mutant subtype, PD-L1 positivity, and a high density of CD8+ T cells; and in patients with poor prognoses. Positive B7-H4 expression was a predictor of improved survival in patients with the NSMP subtype independent of tumor stage or pathologic features. Conclusions.— The NSMP subgroup of endometrial cancer can be further stratified by B7-H4 status. Incorporating B7-H4 status into the molecular classification of NSMP could improve the ability to predict disease relapse.

Advancing Precision Oncology: Whole-Exome Sequencing in Endometrial Cancer Liquid-Based Cytology

Context.— Diagnostic strategies for endometrial cancer have been evolving, with cytologic analysis being considered a key method in integrated oncologic diagnostics because of its less invasive nature and adaptability to various assessments. Liquid-based cytology (LBC) has emerged as a promising method for intact DNA preservation; it exhibits improved efficiency in advanced sequencing applications such as next-generation sequencing. However, despite the use of LBC in panel assays, its application in whole-exome sequencing (WES) for comprehensive genomic profiling remains underexplored. Objective.— To investigate whether molecular classification is possible based on WES using DNA derived from LBC specimens. Design.— We combined WES with targeted gene panel analysis to compare genomic findings of LBC and traditional tissue samples obtained from 7 cases of endometrial cancer. We investigated pathogenic mutations, tumor mutational burden, and microsatellite instability, and achieved molecular classification with high accuracy. Results.— We found a substantial concordance between LBC and traditional tissue samples in terms of pathogenic mutation detection, with a 95% match in the LBC samples and 94% in the tissue samples. Notably, our results highlight the importance of combining WES with panel-based analysis in identifying the ultramutated status of a case that had been missed during panel analysis. Conclusions.— Our findings emphasize the potential of LBC samples in the precise and noninvasive genomic analysis of cases of endometrial cancer and offer a new avenue for developing diagnostic and therapeutic strategies in precision oncology.

Evaluation of the Accuracy of a Polymerase Chain Reaction–Based Assay for Polymerase Epsilon Mutation Detection in Endometrial Carcinoma

Context.— Molecular stratification of endometrial carcinoma provides more accurate prognostic information than traditional clinicopathologic features. However, because next-generation sequencing is typically recommended for polymerase epsilon (POLE) mutation detection, the practical application of a test based on molecular stratification is limited in the clinical setting. Objective.— To evaluate a polymerase chain reaction (PCR)–based assay for POLE mutation detection in endometrial carcinoma. Design.— We developed a PCR-based technology called Dalton Mutation Identifier Technology (Dalton-MIT) that targets 9 mutation sites within POLE exons. Endometrial carcinoma specimens from 613 patients were tested for POLE mutations. Correlations between POLE mutations and patient clinicopathologic characteristics and prognosis were analyzed. Results.— PCR detection data showed that the incidence rate of POLE mutation was 11.4% (70 of 613). Patients with POLE mutations had better clinicopathologic characteristics and prognosis than those with non–POLE mutations. Comparison between Dalton-MIT and next-generation sequencing in 59.5% (365 of 613) of specimens showed that the sensitivity of Dalton-MIT for detecting POLE pathogenic mutations was 100%, the specificity was 99.3%, the Youden index was .993, and the κ value was .981 (P < .001). Conclusions.— Our data demonstrate that POLE mutation detection by Dalton-MIT correlates with next-generation sequencing. This suggests that Dalton-MIT represents a promising alternative assay for detecting POLE mutations and will facilitate the wider application of molecular stratification tools for endometrial carcinoma in the clinic.

Special Considerations in Classification and Workup of Endometrial Carcinomas

Context.— A variety of uncommon malignant endometrial tumors can be challenging to diagnose because of overlapping morphology with more common entities. In some cases, immunohistochemical stains and/or molecular testing allow for more definitive diagnosis or prognostication. Objective.— To review classic morphologic features of uncommon endometrial tumors, pathologic features of these tumors and their mimics, and the evidence for use of immunohistochemistry and molecular testing in the diagnosis of these tumors. Data Sources.— University of Michigan (Ann Arbor) cases and review of pertinent literature about each entity. Conclusions.— Although each of these uncommon endometrial tumors has morphologic mimics, key histologic features, immunohistochemical stains, and molecular testing allow for accurate classification.

Current Laboratory Testing Practices for Assessment of ERBB2 /HER2 in Endometrial Serous Carcinoma and Colorectal Carcinoma

Context.— Therapy targeted at human epidermal growth factor receptor 2 (HER2; also known as ERBB2) was used initially for breast and gastroesophageal carcinoma and has more recently been adopted for endometrial serous carcinoma (ESC) and colorectal carcinoma (CRC). There is evidence that predictive biomarker testing algorithms for HER2 must be tumor type specific and that an algorithm validated for one tumor type cannot be applied to another. Objective.— To describe current laboratory practices for HER2 assessment in ESC and CRC. Design.— We surveyed laboratories participating in the 2021 College of American Pathologists (CAP) HER2 immunohistochemistry proficiency testing program. Results.— The survey was distributed to 1548 laboratories and returned by 1195, of which 83.5% (998) were in the United States. For ESC, 24.0% (287) of laboratories reported performing in-house testing for HER2 by immunohistochemical staining and/or in situ hybridization; of these, 44.3% (127) performed it reflexively on all cases of ESC. The most common criterion for evaluating HER2 was the American Society of Clinical Oncology/CAP 2018 guideline for breast carcinoma (69.0%; 194 of 281), whereas only 16.0% (45) of laboratories used guidelines specific to ESC. For CRC, 20.2% (239 of 1185) of laboratories performed in-house HER2 testing, and 82.0% of these (196) did the test only at the clinician’s request. A plurality (49.4%; 115 of 233) used gastroesophageal cancer guidelines when scoring CRC, 30.0% (70) used the CRC scoring system from the HERACLES trial, and 16.3% (38) used the American Society of Clinical Oncology/CAP 2018 guideline for breast carcinoma. Conclusions.— Laboratories vary in their approach to HER2 testing in ESC and CRC. Most laboratories did not report using tumor type–specific recommendations for HER2 interpretation. The lack of standardization could present a challenge to evidence-based practice when considering targeted therapy for these diseases.

Characteristics of HER2 Gene Amplification by Fluorescence In Situ Hybridization in Endometrial Serous Carcinoma: Implications for Clinical HER2 Testing and Interpretation

Context.— Targeted anti–human epidermal growth factor receptor 2 (HER2) therapy has recently become the standard for advanced-stage and recurrent HER2-positive endometrial serous carcinoma (ESC) in the United States, and an endometrial carcinoma–specific HER2 testing algorithm has been proposed. However, comprehensive studies on the specific features of HER2 gene amplification in these tumors are lacking. Objective.— To evaluate the characteristics of HER2 amplification in ESC in the context of breast and gastric HER2 fluorescence in situ hybridization (FISH) guidelines. Design.— Ninety-four ESCs with available HER2 immunohistochemistry (IHC) and FISH were included. HER2 IHC was scored according to the proposed endometrial carcinoma–specific algorithm, and FISH was evaluated by using the 2018 ESC clinical trial criteria, the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) 2016 gastric criteria, and the ASCO/CAP 2013 and 2018 breast criteria. Results.— Most tumors (90.4%; 85 of 94) had a 2+ HER2 IHC score. Polysomy of chromosome 17 was present in 16% (15 of 94) and monosomy 17 was seen in 2% (2 of 94) of tumors. HER2 FISH interpretation per the clinical trial criteria (HER2/CEP17 ratio ≥ 2.0) showed 99% concordance with the current gastric and breast HER2 FISH interpretations. Conclusions.— Our results support the clinical trial criteria for HER2 FISH in ESC with a modification to include HER2 IHC 2+ and HER2/CEP17 ratio less than 2.0 and average HER2 copy number of 6.0 or greater in the HER2-positive category. Future prospective clinical investigations are necessary to assess the correlation between specific HER2 FISH result categories and therapeutic response.

Endometrial Polyp in Postmenopausal Women: An Epicenter for the Development of Endometrial Serous Carcinoma

Context.— Endometrial serous carcinoma is well known for its high risk of extrauterine spread, even when the intrauterine tumor is minimal in volume and limited to the endometrium. Representing the earliest recognizable forms of endometrial serous carcinoma, minimal uterine serous carcinoma (MUSC) includes serous endometrial intraepithelial carcinoma and superficial serous carcinoma. Objective.— To discuss the pathogenetic relationship between MUSC and endometrial polyp, and to review the pathologic diagnosis and clinical implication of MUSC. Data Sources.— Sources are a literature review and the author's personal practice and perspective. Conclusions.— A close topographic relationship between MUSC and endometrial polyp has been consistently observed in many studies: more than two-thirds of MUSCs involve an endometrial polyp and >50% of MUSCs are confined to an endometrial polyp at the time of staging hysterectomy, indicating that most if not all MUSCs arise in an endometrial polyp. Timely diagnostic recognition of MUSC is clinically critical because the patients without extrauterine tumor spread have an excellent prognosis and those with extrauterine involvement have a dismal outcome. Further investigations into the endometrial polyp harboring MUSC may elucidate the key cellular and molecular alterations underpinning the pathogenesis of uterine serous carcinoma.

Adequacy of Histopathology Reports Representing Oncologic Resection Specimens: An Experience of Reporting Practice in Rural India

Context.— The histopathology reporting practice in rural areas is largely variable. To ensure the adequacy of histopathology reports (HPRs), the College of American Pathologists (CAP) has developed cancer reporting checklists. Objective.— To assess the adequacy of resection specimen HPRs received from outside centers for a second opinion. Further, the adequacy of breast resection HPRs from these centers was compared with that of our center. Additionally, the reports representing endometrial carcinoma were assessed for impact on the treatment decision. Design.— This was a retrospective study conducted from June 2015 to December 2019. HPRs from outside centers and our institute were analyzed for mandatory reporting elements as per CAP 2013 checklists. Results.— A total of 730 HPRs (558 outside HPRs and 172 in-house breast HPRs) were reviewed for completeness. The outside HPRs were complete in 42 of 558 cases (7.5%). Only 11 of 143 reports (7.7%) from the academic centers were complete. Seventeen of 249 outside breast HPRs (6.8%) were complete, whereas predominant (n = 123 of 172; 71.5%) in-house breast HPRs were adequate. Most outside endometrial carcinoma reports (60.8%; n = 28 of 46) were inadequate with potential impact on the adjuvant treatment, whereas 10 of 46 reports (21.7%) were inadequate and had an actual impact on the adjuvant treatment decision. Conclusions.— Minimal data set reporting using checklists is not yet widely operational in most rural laboratories. We call for continuous education and sensitization of the practicing pathologists, oncopathology education of the trainees, and regulatory standards for signing out an oncopathology report.

Evaluating Mismatch Repair/Microsatellite Instability Status Using Cytology Effusion Specimens to Determine Eligibility for Immunotherapy

Context.— The approval of pembrolizumab for treatment of patients with microsatellite instability-high (MSI-H) or mismatch repair–deficient (dMMR) advanced cancers has led to increased requests for MSI and/or MMR immunoperoxidase (IPOX) testing. Diagnoses for patients with advanced-stage cancer are frequently made from cytology specimens. Objective.— To investigate the feasibility of using cell block (CB) preparations of effusions for MMR IPOX evaluation. Design.— Surgical pathology cases of colorectal and endometrial carcinomas with known MMR/MSI status and matched effusions with available CBs were identified. Cell block sections were evaluated for adequacy and stained with MMR IPOX (MSH2, MSH6, MLH1, and PMS2). The CBs were reviewed, the number of tumor cells quantified, and MMR IPOX was interpreted as retained, lost, suboptimal, or noncontributory. Results.— We identified 748 cases with MMR/MSI testing on surgical specimens having matched effusions. Of these, 131 cases (17.5%) had an available CB and 53 were deemed adequate for MMR IPOX staining. MMR IPOX results between effusion CBs and surgical pathology specimens were concordant in 45 of 53 (85%), inconclusive in 6 of 53 (11%), and discordant in 2 of 53 (4%) cases. Conclusions.— There was high concordance of MMR IPOX testing between cytologic and surgical specimens, with no false-positive and 2 false-negative CB results. Limited tumor cells, staining in cells indefinite as tumor, tumor staining heterogeneity, and lack of internal control staining were problematic in some cases. Our findings indicate that cytologic effusion specimens may be suitable substrates for MMR IPOX biomarker testing; however, inconclusive cases need to be interpreted with caution.