Human Papillomavirus-Associated Multiphenotypic Carcinoma: First Description of a Vulval Case.

Human papillomavirus (HPV)-associated multiphenotypic sinonasal carcinoma is a rare and recently described epithelial neoplasm exhibiting myoepithelial differentiation and morphological overlap with salivary gland neoplasms, especially adenoid cystic carcinoma; it is commonly associated with HPV, especially type 33. It has mainly been reported in the nasal cavity and paranasal sinuses with a single case reported in the breast. Herein, we report the first vulval example in a 47-year-old patient who presented with a large craggy mass in the region of the Bartholin gland. The histologic features were of a high-grade carcinoma composed of basaloid cells arranged in sheets and nests, with occasional ductal formations, surrounded by densely hyalinised basement membrane-type material. There was diffuse block-type immunoreactivity with p16 and HPV genotyping revealed high-risk HPV type 16. In reporting this case, we highlight the propensity for "salivary gland-type" neoplasms to arise in the vulva, especially in the Bartholin gland, and stress that pathologists should consider salivary-type neoplasms when faced with a morphologically unusual vulval tumor.

Factors associated with interobserver variation amongst pathologists in the diagnosis of endometrial hyperplasia: A systematic review.

OBJECTIVE: Reproducible diagnoses of endometrial hyperplasia (EH) remains challenging and has potential implications for patient management. This systematic review aimed to identify pathologist-specific factors associated with interobserver variation in the diagnosis and reporting of EH. METHODS: Three electronic databases, namely MEDLINE, Embase and Web of Science, were searched from 1st January 2000 to 25th March 2023, using relevant key words and subject headings. Eligible studies reported on pathologist-specific factors or working practices influencing interobserver variation in the diagnosis of EH, using either the World Health Organisation (WHO) 2014 or 2020 classification or the endometrioid intraepithelial neoplasia (EIN) classification system. Quality assessment was undertaken using the QUADAS-2 tool, and findings were narratively synthesised. RESULTS: Eight studies were identified. Interobserver variation was shown to be significant even amongst specialist gynaecological pathologists in most studies. Few studies investigated pathologist-specific characteristics, but pathologists were shown to have different diagnostic styles, with some more likely to under-diagnose and others likely to over-diagnose EH. Some novel working practices were identified, such as grading the "degree" of nuclear atypia and the incorporation of objective methods of diagnosis such as semi-automated quantitative image analysis/deep learning models. CONCLUSIONS: This review highlighted the impact of pathologist-specific factors and working practices in the accurate diagnosis of EH, although few studies have been conducted. Further research is warranted in the development of more objective criteria that could improve reproducibility in EH diagnostic reporting, as well as determining the applicability of novel methods such as grading the degree of nuclear atypia in clinical settings.

Gastric-type glandular lesions of the female genital tract excluding the cervix: emerging pathological entities.

In the last two decades or so, a spectrum of benign, premalignant and malignant cervical glandular lesions exhibiting gastric differentiation has been described, with gastric-type adenocarcinoma representing the most common human papillomavirus (HPV)-independent cervical adenocarcinoma. More recently, limited literature has reported a variety of gastric-type glandular lesions at other sites within the female genital tract and, as in the cervix (the most common site for these lesions), a spectrum of benign, premalignant and malignant lesions has been proposed. We provide an update and review of the emerging spectrum of gastric-type glandular lesions at female genital tract sites other than the cervix. In the endometrium, putative gastric-type glandular lesions include mucinous metaplasia of gastric-type, atypical mucinous proliferation of gastric-type and gastric-type adenocarcinoma. Similarly in the vagina, gastric-type adenosis, atypical adenosis and adenocarcinoma have been described. There have also been occasional reports of gastric-type lesions involving the ovary and fallopian tube. We provide guidance on how to recognise gastric-type lesions morphologically and immunophenotypically and stress that sometimes these lesions occur at more than one site within the female genital tract (synchronous/multifocal gastric-type lesions of the female genital tract), sometimes in association with Peutz-Jeghers syndrome.

The malignant transformation of endometriosis: Is there a left lateral predisposition of ovarian clear cell and endometrioid carcinomas?

INTRODUCTION: Endometriosis affects 10% of women of reproductive age. There is evidence for a left lateral predisposition of endometriotic lesions and a 1.9-fold greater risk of ovarian cancer in endometriosis. The aim of this study is to determine whether a left lateral predisposition of ovarian clear-cell carcinoma (CCC) and endometrioid carcinoma (EC) exists. MATERIALS AND METHODS: A retrospective cohort study of all EC and CCC patients in Northern Ireland between March-2011 and June-2018. ANOVA was used to analyse preoperative prediction of stage, chi-squared (χ2) was used to compare left- and right-sided masses. Survival was estimated using Kaplan-Meier and log-rank test. A p-value <0.05 was considered significant. RESULTS: 158 patients were identified (95 EC, 55 CCC, 8 mixed). Mean age was 57.65 years with 69% presenting at stage 1. The mean CA125 was 559 U/mL (p = 0.850) and mean abdominal mass size was 14.12 cm (p = 0.732). The most common presenting symptom was an abdominal mass (37%). Despite 67% of patients having endometriosis on final pathology, only 8.9% had a known history pre-operatively. 51% of tumours were located on the left (p = 0.036). For unilateral tumours this was significant for EC (P = 0.002) but not for CCC (P = 0.555). The 1-, 3- and 5-year overall survival for all types/stages was 85%, 78% and 71% respectively. CONCLUSION: While CCC and EC are associated with endometriosis, only EC exhibits a left lateral predisposition. There is no association between preoperative CA125 or abdominal mass size and stage of disease.

Cost-Effectiveness of Gene-Specific Prevention Strategies for Ovarian and Breast Cancer.

Importance: Pathogenic variants (PVs) in BRCA1, BRCA2, PALB2, RAD51C, RAD51D, and BRIP1 cancer susceptibility genes (CSGs) confer an increased ovarian cancer (OC) risk, with BRCA1, BRCA2, PALB2, RAD51C, and RAD51D PVs also conferring an elevated breast cancer (BC) risk. Risk-reducing surgery, medical prevention, and BC surveillance offer the opportunity to prevent cancers and deaths, but their cost-effectiveness for individual CSGs remains poorly addressed. Objective: To estimate the cost-effectiveness of prevention strategies for OC and BC among individuals carrying PVs in the previously listed CSGs. Design, Setting, and Participants: In this economic evaluation, a decision-analytic Markov model evaluated the cost-effectiveness of risk-reducing salpingo-oophorectomy (RRSO) and, where relevant, risk-reducing mastectomy (RRM) compared with nonsurgical interventions (including BC surveillance and medical prevention for increased BC risk) from December 1, 2022, to August 31, 2023. The analysis took a UK payer perspective with a lifetime horizon. The simulated cohort consisted of women aged 30 years who carried BRCA1, BRCA2, PALB2, RAD51C, RAD51D, or BRIP1 PVs. Appropriate sensitivity and scenario analyses were performed. Exposures: CSG-specific interventions, including RRSO at age 35 to 50 years with or without BC surveillance and medical prevention (ie, tamoxifen or anastrozole) from age 30 or 40 years, RRM at age 30 to 40 years, both RRSO and RRM, BC surveillance and medical prevention, or no intervention. Main Outcomes and Measures: The incremental cost-effectiveness ratio (ICER) was calculated as incremental cost per quality-adjusted life-year (QALY) gained. OC and BC cases and deaths were estimated. Results: In the simulated cohort of women aged 30 years with no cancer, undergoing both RRSO and RRM was most cost-effective for individuals carrying BRCA1 (RRM at age 30 years; RRSO at age 35 years), BRCA2 (RRM at age 35 years; RRSO at age 40 years), and PALB2 (RRM at age 40 years; RRSO at age 45 years) PVs. The corresponding ICERs were -£1942/QALY (-$2680/QALY), -£89/QALY (-$123/QALY), and £2381/QALY ($3286/QALY), respectively. RRSO at age 45 years was cost-effective for RAD51C, RAD51D, and BRIP1 PV carriers compared with nonsurgical strategies. The corresponding ICERs were £962/QALY ($1328/QALY), £771/QALY ($1064/QALY), and £2355/QALY ($3250/QALY), respectively. The most cost-effective preventive strategy per 1000 PV carriers could prevent 923 OC and BC cases and 302 deaths among those carrying BRCA1; 686 OC and BC cases and 170 deaths for BRCA2; 464 OC and BC cases and 130 deaths for PALB2; 102 OC cases and 64 deaths for RAD51C; 118 OC cases and 76 deaths for RAD51D; and 55 OC cases and 37 deaths for BRIP1. Probabilistic sensitivity analysis indicated both RRSO and RRM were most cost-effective in 96.5%, 89.2%, and 84.8% of simulations for BRCA1, BRCA2, and PALB2 PVs, respectively, while RRSO was cost-effective in approximately 100% of simulations for RAD51C, RAD51D, and BRIP1 PVs. Conclusions and Relevance: In this cost-effectiveness study, RRSO with or without RRM at varying optimal ages was cost-effective compared with nonsurgical strategies for individuals who carried BRCA1, BRCA2, PALB2, RAD51C, RAD51D, or BRIP1 PVs. These findings support personalizing risk-reducing surgery and guideline recommendations for individual CSG-specific OC and BC risk management.

SMARCB1 (INI1) Deficient Tumours of the Uterine Cervix: Report of Two Cases, Including One Associated With an NTRK Fusion.

Pathogenic variants (mutations) and other molecular events involving subunits of the SWItch/Sucrose Non-Fermentable chromatin remodelling complex are common in a wide variety of malignancies. Many of these neoplasms are characterized by undifferentiated morphology. They arise at a variety of sites in the female genital tract but have rarely been reported in the uterine cervix. We report 2 primary cervical neoplasms arising in young women (ages 28 and 29 yr) exhibiting loss of nuclear immunoreactivity with SMARCB1 (INI1). In one case, which had a mixture of epithelioid and spindle cells, molecular studies revealed no SMARCB1 pathogenic variant, but showed a SPECCL1::NTRK 3 fusion, in keeping with an NTRK fusion sarcoma. The second case exhibited rhabdoid morphology and molecular testing confirmed a SMARCB1 pathogenic variant (c.425 T>G:p.(Leu142Ter) which, interpreted in conjunction with the morphology and immunohistochemistry, resulted in classification as a proximal-type epithelioid sarcoma. To our knowledge, this is the first reported cervical neoplasm exhibiting a SMARCB1 pathogenic variant and the first NTRK fusion sarcoma showing SMARCB1 protein loss. We discuss the diagnostic challenges and complexities of the molecular findings.

Teratoma-associated and so-called pure Wilms tumour of the ovary represent two separate tumour types with distinct molecular features.

AIMS: Ovarian Wilms tumour (WT)/nephroblastoma is an extremely rare neoplasm that has been reported to occur in pure form or as a component of a teratomatous neoplasm. We hypothesized that teratoma-associated and pure ovarian WT may represent different tumour types with diverging molecular backgrounds. To test this hypothesis, we comprehensively characterized a series of five tumours originally diagnosed as ovarian WT. METHODS AND RESULTS: The five cases comprised three teratoma-associated (two mature and one immature) and two pure WTs. Two of the teratoma-associated WTs consisted of small nodular arrangements of "glandular"/epithelial structures, while the third consisted of both an epithelial and a diffuse spindle cell/blastemal component. The pure WTs consisted of "glandular" structures, which were positive for sex cord markers (including inhibin and SF1) together with a rhabdomyosarcomatous component. The two pure WTs harboured DICER1 pathogenic variants (PVs), while the three associated with teratomas were DICER1 wildtype. Panel-based DNA sequencing of four of the cases did not identify PVs in the other genes investigated. Analysis of the HA19/IGF2 imprinting region showed retention of imprinting in the pure WTs but loss of heterozygosity with hypomethylation of the ICR1 region in two of three teratoma-associated WTs. Furthermore, copy number variation and clustering-based whole-genome DNA methylation analyses identified divergent molecular profiles for pure and teratoma-associated WTs. CONCLUSION: Based on the morphological features, immunophenotype, and molecular findings (DICER1 PVs, copy number, and DNA methylation profiles), we suggest that the two cases diagnosed as pure primary ovarian WT represent moderately to poorly differentiated Sertoli Leydig cell tumours (SLCTs), while the tumours arising in teratomas represent true WTs. It is possible that at least some prior cases reported as pure primary ovarian WT represent SLCTs.

Neuroendocrine Marker Expression in Primary Non-neuroendocrine Epithelial Tumors of the Ovary: A Study of 551 Cases.

Expression of neuroendocrine (NE) markers in primary ovarian non-NE epithelial tumors has rarely been evaluated. The aim of our study was to evaluate the expression of the most widely used NE markers in these neoplasms and to determine any prognostic significance of NE marker expression. The cohort consisted of 551 primary ovarian tumors, including serous borderline tumors, low-grade serous carcinomas, high-grade serous carcinomas (HGSC), clear cell carcinomas, endometroid carcinomas, mucinous borderline tumors, and mucinous carcinomas. Immunohistochemical analysis was performed using antibodies against INSM1, synaptophysin, chromogranin, and CD56 on tissue microarray. Positivity for INSM1, synaptophysin, chromogranin, and CD56 was most frequently observed in mucinous tumors (48.7%, 26.0%, 41.5%, and 100%, respectively). The positivity for these NE markers was mostly restricted to nonmucinous elements distributed throughout the tumor. The mucinous borderline tumor and mucinous carcinomas groups had similar proportions of positivity (mucinous borderline tumor: 53%, mucinous carcinomas: 39%). In the other tumor types, except for HGSC, there was only focal expression (5%-10%) or negativity for NE markers. HGSC showed high CD56 expression (in 26% of cases). Survival analysis was only performed for CD56 in HGSC as this was the only group with sufficient positive cases, and it showed no prognostic significance. Except for mucinous tumors, expression of NE markers in non-NE ovarian epithelial tumors is low. CD56 expression in HGSC occurs frequently but is without diagnostic or prognostic value.

"Deciduoid" Change in Uterine Leiomyomas in Pregnancy: Aberrant Expression of Sex Cord Markers Inhibin and Calretinin.

Leiomyomas are common hormone-responsive uterine neoplasms which can exhibit a variety of morphologic changes secondary to hormonal agents such as progestogens. They may increase in size during pregnancy as a result of hormonal stimulation but surprisingly the morphologic features of leiomyomas in pregnancy are not well described in the literature. In this report, we describe the morphologic features of a series of 29 uterine leiomyomas in pregnancy. The features include in decreasing order of frequency infarct-type necrosis, decidualization of the serosal surface, hyalinization, myxoid alteration of the stroma, edema (sometimes with cyst formation), and dystrophic calcification. We also report a feature which we term "deciduoid" change (seen in 10 of 29 leiomyomas) which takes the form of altered smooth muscle cells with an epithelioid morphology with abundant eosinophilic or clear cytoplasm. Furthermore, we show that the "deciduoid" cells commonly exhibit expression of sex cord markers inhibin and calretinin. We speculate on the pathogenesis of the "deciduoid" change which together with its "aberrant" immunophenotype may result in diagnostic problems and consideration of other neoplasms.

Macroscopic examination of pathology specimens: a critical reappraisal.

Meticulous macroscopic examination of specimens and tissue sampling are crucial for accurate histopathology reporting. However, macroscopy has generally received less attention than microscopy and may be delegated to relatively inexperienced practitioners with limited guidance and supervision. This introductory paper in the minisymposium, Macroscopy Under the Microscope, focuses on issues regarding macroscopic examination and tissue sampling that have been insufficiently addressed in the published literature. It highlights the importance of specimen examination and sampling, discusses some general principles, outlines challenges and suggests potential solutions. It is critical to get macroscopy right the first time as it may not be possible to rectify errors even with expert histological assessment or to retrospectively collect missing data after the specimen retention period. Dissectors must, therefore, receive adequate guidance and supervision until they are proficient in macroscopic specimen examination. We emphasise the importance of the clinical context, optimal specimen fixation, succinct and clinically relevant macroscopic descriptions, macrophotography and judicious tissue sampling. We note that current recommendations based on the number of blocks to be submitted per maximum tumour dimension are ambiguous as the amount of tissue submitted in a cassette is not standardised and it is unclear whether 'block' refers to a tissue block or a paraffin block. Concerns around potential oversampling of 'therapeutic' specimens that could result in overdiagnosis due to detection of incidentalomas are also discussed. We hope that the issues discussed in this paper will engender debate on this clinically critical aspect of pathology practice.

Cervical Adenoid Basal Carcinoma With High-grade Squamous Component: True Mixed Carcinoma or Colonization of Adenoid Basal Carcinoma by High-grade Squamous Intraepithelial Lesion?

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

Dedifferentiated and Undifferentiated Ovarian Carcinoma: An Aggressive and Molecularly Distinct Ovarian Tumor Characterized by Frequent SWI/SNF Complex Inactivation.

Dedifferentiated and undifferentiated ovarian carcinomas (DDOC/UDOC) are rare neoplasms defined by the presence of an undifferentiated carcinoma. In this study, we detailed the clinical, pathological, immunohistochemical, and molecular features of a series of DDOC/UDOC. We collected a multi-institutional cohort of 23 DDOC/UDOC and performed immunohistochemistry for core switch/sucrose nonfermentable (SWI/SNF) complex proteins (ARID1A, ARID1B, SMARCA4, and SMARCB1), mismatch repair (MMR) proteins, and p53. Array-based genome-wide DNA methylation and copy number variation analyses were performed on a subset of cases with comparison made to a previously reported cohort of undifferentiated endometrial carcinoma (UDEC), small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), and tubo-ovarian high-grade serous carcinoma (HGSC). The age of all 23 patients with DDOC/UDOC ranged between 22 and 71 years (with an average age of 50 years), and a majority of them presented with extraovarian disease (16/23). Clinical follow-up was available for 19 patients. Except for 2 patients, the remaining 17 patients died from disease, with rapid disease progression resulting in mortality within a year in stage II-IV settings (median disease-specific survival of 3 months). Eighteen of 22 cases with interpretable immunohistochemistry results showed loss of expression of core SWI/SNF protein(s) that are expected to result in SWI/SNF complex inactivation as 10 exhibited coloss of ARID1A and ARID1B, 7 loss of SMARCA4, and 1 loss of SMARCB1. Six of 23 cases were MMR-deficient. Two of 20 cases exhibited mutation-type p53 immunoreactivity. Methylation profiles showed coclustering of DDOC/UDOC with UDEC, which collectively were distinct from SCCOHT and HGSC. However, DDOC/UDOC showed an intermediate degree of copy number variation, which was slightly greater, compared with SCCOHT but much less compared with HGSC. Overall, DDOC/UDOC, like its endometrial counterpart, is highly aggressive and is characterized by frequent inactivation of core SWI/SNF complex proteins and MMR deficiency. Its molecular profile overlaps with UDEC while being distinct from SCCOHT and HGSC.

Pan-TRK immunohistochemistry in gynaecological mesenchymal tumours: diagnostic implications and pitfalls.

AIMS: NTRK-rearranged sarcomas of the female genital tract mainly occur in the uterus (more commonly cervix than corpus) and are characterized by a "fibrosarcoma-like" morphology and NTRK gene rearrangements. These neoplasms may exhibit histological overlap with other entities and can present diagnostic difficulties without molecular confirmation. Pan-TRK immunohistochemistry was developed to identify tumours harbouring NTRK rearrangements. The aim of this study was to characterize pan-TRK immunohistochemical expression in a large cohort of gynaecological mesenchymal neoplasms and investigate the utility of pan-TRK immunohistochemistry to distinguish NTRK-rearranged sarcoma from its mimics. METHODS AND RESULTS: A total of 473 gynaecological mesenchymal tumours (461 without known NTRK fusions and 12 NTRK-rearranged sarcomas) were selected. Pan-TRK immunohistochemistry (EPR17341, Abcam) was performed on whole tissue sections and tissue microarrays. Molecular interrogation of pan-TRK positive tumours was performed by RNA sequencing or fluorescence in situ hybridization (FISH). Of the 12 NTRK-rearranged sarcomas, 11 (92%) exhibited diffuse (≥70%) cytoplasmic pan-TRK staining with moderate/marked intensity, while the other was negative. Eleven (2.4%) additional tumours also exhibited pan-TRK immunohistochemical expression: three low-grade endometrial stromal sarcomas, seven high-grade endometrial stromal sarcomas, and an undifferentiated uterine sarcoma. Molecular confirmation of the absence of NTRK rearrangements was possible in nine of these tumours. Of these nine neoplasms, seven exhibited focal/multifocal (<70%) pan-TRK cytoplasmic staining with weak/moderate intensity. CONCLUSION: Even though pan-TRK immunohistochemical expression is not entirely sensitive or specific for NTRK-rearranged sarcomas, these neoplasms tend to exhibit diffuse staining of moderate/strong intensity, unlike its mimics. Pan-TRK should be performed in monomorphic uterine (corpus and cervix) spindle cell neoplasms that are negative for smooth muscle markers and hormone receptors and positive for CD34 and/ or S100. Ultimately, the diagnosis requires molecular confirmation.

Mullerian Polyp of the Vagina: Report of Three Cases of a Previously Undescribed Lesion With Discussion of the Differential Diagnosis.

Benign and malignant neoplasms of the vagina are rare. We report 3 primary vaginal polypoid lesions involving the upper or mid-vagina in patients aged 40, 60, and 67 years. The lesions bore a striking morphologic resemblance to benign endocervical or endometrial polyps and we suggest the designation Mullerian polyp of the vagina. As far as we are aware, similar cases have not been reported previously in the literature. Follow-up ranging from 6 to 21 months has been uneventful. In reporting these cases, we discuss the possible origin and differential diagnosis and review vaginal lesions with a benign glandular component.

FIGO 2023 endometrial cancer staging: too much, too soon?

An updated International Federation of Gynecology and Obstetrics (FIGO) staging system for endometrial carcinoma was introduced in June 2023. The new system represents a significant departure from traditional endometrial and other gynecological carcinoma staging systems which are agnostic of parameters such as tumor type, tumor grade, lymphovascular space invasion, and molecular alterations. The updated system, which incorporates all of these 'non-anatomical' parameters, is an attempt to make staging more personalized and relevant to patient prognostication and management, and to align with the European Society of Gynaecological Oncology/European Society for Radiotherapy and Oncology/European Society of Pathology (ESGO/ESTRO/ESP) risk stratification. Herein, we present a critical review of the new staging system and discuss its advantages and disadvantages. The authors propose that the new FIGO staging system should be first appraised at a multi-institutional and global level with the input of all relevant societies (gynecology, pathology, gynecologic oncology, medical oncology, radiation oncology) to understand the impact, scope, and supporting evidence of the proposed changes. Such a process is fundamental to produce a robust system that pathologists and treating clinicians can adopt.

Clinicopathologic Analysis and Molecular Profiling of Ovarian Steroid Cell Tumors.

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

Clinical Behavior and Molecular Landscape of Stage I p53-Abnormal Low-Grade Endometrioid Endometrial Carcinomas.

PURPOSE: The clinical significance of the p53-abnormal (p53abn) molecular subtype in stage I low-grade endometrioid endometrial carcinoma (EEC) is debated. We aimed to review pathologic and molecular characteristics, and outcomes of stage I low-grade p53abn EEC in a large international cohort. EXPERIMENTAL DESIGN: Previously diagnosed stage I p53abn EC (POLE-wild-type, mismatch repair-proficient) low-grade EEC from Canadian retrospective cohorts and PORTEC-1&2 trials were included. Pathology review was performed by six expert gynecologic pathologists blinded to p53 status. IHC profiling, next-generation sequencing, and shallow whole-genome sequencing was performed. Kaplan-Meier method was used for survival analysis. RESULTS: We identified 55 stage I p53abn low-grade EEC among 3,387 cases (2.5%). On pathology review, 17 cases (31%) were not diagnosed as low-grade EEC by any pathologists, whereas 26 cases (47%) were diagnosed as low-grade EEC by at least three pathologists. The IHC and molecular profile of the latter cases were consistent with low-grade EEC morphology (ER/PR positivity, patchy p16 expression, PIK3CA and PTEN mutations) but they also showed features of p53abn EC (TP53 mutations, many copy-number alterations). These cases had a clinically relevant risk of disease recurrence (5-year recurrence-free survival 77%), with pelvic and/or distant recurrences observed in 12% of the patients. CONCLUSIONS: A subset of p53abn EC is morphologically low-grade EEC and exhibit genomic instability. Even for stage I disease, p53abn low-grade EEC are at substantial risk of disease recurrence. These findings highlight the clinical relevance of universal p53-testing, even in low-grade EEC, to identify women at increased risk of recurrence.