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Endometrial carcinoma (EC) can be divided into 4 prognostic molecular subtypes, and no specific molecular profile (NSMP) type is the most commonly occurring type (∼50%). Although described as having an intermediate to favorable prognosis, this subtype encompasses pathologically and molecularly diverse tumors. We aimed to identify factors associated with outcomes within the NSMP ECs that might be used to stratify prognosis and direct treatment. Clinicopathologic, immunohistochemical, and genetic features of a large series of NSMP EC were used to identify parameters that could identify the subset associated with a very favorable outcome (disease-specific death rate <5% at 5 years, termed low-risk NSMP). A total of 1110 NSMP ECs were profiled. In a univariate analysis, stage, grade, lymphovascular invasion, estrogen receptor (ER) and progesterone receptor (PR) expression, L1CAM overexpression, and mutations in PIK3CA were associated with disease-specific survival. Two critical features, grade and ER expression, identified a low-risk NSMP subset (grade 1-2, ER-positive [>1%], 84% of cases), which showed a 5-year disease-specific death rate of 1.6% across all stages and 1.4% within stage I. The remaining cases (high-risk NSMPs, grade 3, and/or ER-negative status) were responsible for most of the disease-specific deaths (disease-specific death rate at 5 years, 22.9%; hazard ratio compared with that of low-risk NSMPs: 16.3; 95% CI, 8.4-31.7). Within NSMP EC, the low-risk and high-risk categories were of prognostic significance independent of the stage on a multivariate analysis. Low-grade and ER-positive NSMP ECs are a homogeneous low-risk group associated with an exceptionally favorable prognosis in which de-escalation and/or endocrine therapy strategies can be applied. Grade 3 and/or ER-negative status identifies a high-risk NSMP subset, including rare high-grade histotypes (eg, clear cell, dedifferentiated, and mesonephric-like), responsible for most NSMP-related deaths. Subclassification of NSMPs allows for the category of low-risk EC molecular subtypes to be dramatically expanded because it now includes both POLEmut and the much more common low-risk NSMP EC., (Copyright © 2022 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights reserved.)

High-grade endometrial stromal sarcomas (HGESSs) are aggressive uterine tumors harboring oncogenic fusion proteins. We performed a molecular study of 36 HGESSs with YWHAE::NUTM2 gene fusion, assessing co-occurring genetic events, and showed that these tumors frequently harbor recurrent events involving the CDKN2A locus on chromosome 9p. Using array-based copy number profiling and CDKN2A fluorescence in situ hybridization, we identified homozygous and hemizygous deletions of CDKN2A in 18% and 14% of tumors (n = 22 analyzed), respectively. While all YWHAE-rearranged HGESSs with retained disomy for CDKN2A were immunohistochemically positive for p16INK4 (p16), all tumors with homozygous deletion of CDKN2A showed complete absence of p16 staining. Of the 2 tumors with a hemizygous deletion of CDKN2A, 1 showed diffuse and strong p16 positivity, whereas the other showed complete absence of staining. In the p16-negative case, we did not find intragenic mutations or DNA promoter methylation to explain the p16 protein loss, implicating other mechanisms in the regulation of protein expression. In our cohort, subclonal or complete absence of p16 staining was associated with worse overall survival compared with positive p16 staining (1-year overall survival: 28.6% vs 90.7%, respectively; n = 32; P < .001), with all 7 patients in the p16-negative group having succumbed to their disease within 2 years of diagnosis. Our results suggested CDKN2A alterations as a cooperative driver of tumorigenesis in a subset of HGESSs with the YWHAE::NUTM2 gene fusion and showed p16 to be a potential prognostic marker., (Copyright © 2022 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights reserved.)

Objectives: Recent data support the predictive implications of molecular subtype assignment in endometrial cancer (EC). Our objective was to retrospectively assess clinical outcomes according to adjuvant treatment received within EC molecular subtypes., Methods: Clinical outcomes (disease-specific and progression-free survival DSS/PFS) of EC patients from a single institution and population-based cohorts that had undergone molecular classification were assessed with respect to adjuvant therapy received and 2016 ESMO risk group., Results: 2472 ECs were assessed; 184 (7.4%) POLEmut, 638 (25.8%) MMRd, 1223 (49.5%) NSMP and 427 (17.3%) p53abn. N = 774 (34.6%) of the cohort were ESMO 2016 high risk and 109 (4.8%) were advanced or metastatic. In patients with MMRd EC, assessed across and within stage, there was no observed benefit in DSS or PFS with the addition of chemotherapy +/- radiation compared to radiation alone in ESMO high risk (p = 0.694) or ESMO high, advanced, metastatic risk groups combined (p = 0.852). In patients with p53abn EC, adjuvant chemotherapy given with radiation was associated with significantly longer DSS compared to radiation alone in ESMO high risk (p = 0.007) and ESMO high, advanced and metastatic risk groups combined (p = 0.015), even when restricted to stage I disease (p < 0.001) and when compared in serous vs. non-serous histotypes (p = 0.009)., Conclusions: Adjuvant chemotherapy is associated with more favorable outcomes for patients with p53abn EC, including stage I disease and non-serous histotypes, but does not appear to add benefit within MMRd ECs for any stage of disease, consistent with PORTEC-3 molecular subanalysis. Prospective trials, assessing treatment efficacy within molecular subtype are needed, however these 'real-world' data should be considered when discussing adjuvant treatment with patients., Competing Interests: Declaration of Competing Interest Dr. McConechy is an employee and Dr. Huntsman is a founder and Chief Medical Officer of Imagia Canexia Health., (Copyright © 2023 Elsevier Inc. All rights reserved.)

We assessed the landscape of diagnostic pathology practice and how molecular classification could potentially impact management of patients with endometrial cancer by collecting patient samples, clinicopathologic data, and patient outcomes from EC patients diagnosed in 2016 at 10 Canadian tertiary cancer centers and 19 community hospitals. ProMisE molecular subtype (POLEmut, MMRd, p53abn, No Specific Molecular Profile (NSMP)) was assigned retrospectively. 1357 patients were fully evaluable including 85 POLEmut (6.3%), 380 MMRd (28.0%), 643 NSMP (47.4%), and 249 p53abn ECs (18.3%). Immunohistochemistry (IHC) for MMR proteins was undertaken at the time of primary diagnosis in 2016 in only 42% of the cohort (570/1357; range 3.5-95.4%/center). p53 IHC had only been performed in 21.1% of the cohort (286/1357; range 10.1-41.9%/center). Thus, based on the retrospective molecular subtype assignment, 54.7% (208/380) of MMRd EC had not been tested with MMR IHC (or MSI) and 48.2% (120/249) of p53abn ECs were not tested with p53 IHC in 2016. Molecular subtype diversity within histotypes was profound; most serous carcinomas were p53abn (91.4%), but only 129/249 (51.8%) p53abn EC were serous. Low-grade (Gr1-2) endometrioid carcinomas were mostly NSMP (589/954, 61.7%) but included all molecular subtypes, including p53abn (19/954, 2.0%). Molecular subtype was significantly associated with clinical outcomes (p < 0.001) even in patients with stage I disease (OS p = 0.006, DSS p < 0.001, PFS p < 0.001). Assessment of national pathologic practice in 2016 shows highly variable use of MMR and p53 IHC and demonstrates significant opportunities to improve and standardize biomarker reporting. Inconsistent, non-reflexive IHC resulted in missed opportunities for Hereditary Cancer Program referral and Lynch Syndrome diagnosis, and missed potential therapeutic implications (e.g., chemotherapy in p53abn EC, immune blockade for MMRd EC). Routine integration of molecular subtyping into practice can improve the consistency of EC pathology assessment and classification., (© 2022. The Author(s), under exclusive licence to United States & Canadian Academy of Pathology.)

The distinction between low-grade and high-grade endometrial stromal sarcomas (LGESS, HGESS) is increasingly defined by genetics. Recently, variant genomic alterations involving BCOR or BCORL1 have been reported in endometrial stromal sarcoma (ESS), although it remains unclear whether these justify a diagnosis of LGESS or HGESS. In this study, we describe clinicopathologic and molecular features of ESS with such alterations to help clarify their classification in the spectrum of ESS. We collected a cohort of 13 ESS harboring variant alteration involving BCOR (6 with internal tandem duplication, 1 with EP300::BCOR fusion, 1 with BCOR::LPP fusion) and BCORL1 ( 4 with JAZF1::BCORL1 fusion, 1 with EPC1::BCORL1 fusion). The median patient age at primary diagnosis was 51 years (range: 18 to 70 y). Median tumor size at primary diagnosis was 9.3 cm (range: 4.5 to 21 cm), and extrauterine disease spread (stage IIIB-C) was present in 27%. The tumors were composed of round to spindled cells with cellularity and cytologic atypia ranging from mild to marked and a median mitotic count of 18/10 HPFs (range: 2 to 85/10 HPFs). At least focally myopermeative growth was noted in 8/8 assessable cases. Of 12 patients with follow-up data (median: 25 mo), 4 patients died of disease and 3 were alive with recurrent disease. Unsupervised hierarchical clustering of DNA methylation data together with a large cohort of uterine mesenchymal tumors that included YWHAE::NUTM2 and Z C3H7B::BCOR HGESS and molecularly confirmed LGESS revealed a common methylation signature for all ESS with variant BCOR and BCORL1 alterations and HGESS with YWHAE::NUTM2 and ZC3H7B::BCOR gene fusion. Copy number analysis revealed amplifications of CDK4 and MDM2 , as well as homozygous deletions of CDKN2A/B and NF1 in a subset of tumors. Our results indicate that ESS with BCOR internal tandem duplication and variant BCOR and BCORL1 rearrangements clinically and molecularly resemble conventional HGESS., Competing Interests: Conflicts of Interest and Source of Funding: Supported by the German Cancer Aid (Grant: 70112499) and the Krebs- und Scharlachforschung Mannheim (F.K.F.K.). F.K.F.K. is funded by the Physician Scientist-Program of Heidelberg University. A.v.D. is recipient of an Illumina research grant. For the remaining authors none were declared., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Objectives: We measured the variation in practice across all aspects of endometrial cancer (EC) management and assessed the potential impact of implementation of molecular classification., Methods: Centers from across Canada provided representative tumor samples and clinical data, including preoperative workup, operative management, hereditary cancer program (HCP) referrals, adjuvant therapy, surveillance and outcomes, for all EC patients diagnosed in 2016. Tumors were classified into the four ProMisE molecular subtypes., Results: A total of 1336 fully evaluable EC patients were identified from 10 tertiary cancer centers (TC; n = 1022) and 19 community centers (CC; n = 314). Variation of surgical practice across TCs was profound (14-100%) for lymphadenectomy (LND) (mean 57% Gr1/2, 82% Gr3) and omental sampling (20% Gr1/2, 79% Gr3). Preoperative CT scans were inconsistently obtained (mean 32% Gr1/2, 51% Gr3) and use of adjuvant chemo or chemoRT in high risk EC ranged from 0-55% and 64-100%, respectively. Molecular subtyping was performed retrospectively and identified 6% POLEmut, 28% MMRd, 48% NSMP and 18% p53abn ECs, and was significantly associated with survival. Within patients retrospectively diagnosed with MMRd EC only 22% had been referred to HCP. Of patients with p53abn EC, LND and omental sampling was not performed in 21% and 23% respectively, and 41% received no chemotherapy. Comparison of management in 2016 with current 2020 ESGO/ESTRO/ESP guidelines identified at least 26 and 95 patients that would have been directed to less or more adjuvant therapy, respectively (10% of cohort)., Conclusion: Molecular classification has the potential to mitigate the profound variation in practice demonstrated in current EC care, enabling reproducible risk assessment, guiding treatment and reducing health care disparities., Competing Interests: Declaration of Competing Interest Dr. M McConechy, and R Aguirre- Hernandez are employees, and Dr. Huntsman is a founder and Chief Medical Officer of Canexia Health., (Crown Copyright © 2022. Published by Elsevier Inc. All rights reserved.)

This review of challenging diagnostic issues concerning high-grade endometrial carcinomas is derived from the authors' review of the literature followed by discussions at the Endometrial Cancer Workshop sponsored by the International Society of Gynecological Pathologists in 2016. Recommendations presented are evidence-based, insofar as this is possible, given that the levels of evidence are weak or moderate due to small sample sizes and nonuniform diagnostic criteria used in many studies. High-grade endometrioid carcinomas include FIGO grade 3 endometrioid carcinomas, serous carcinomas, clear cell carcinomas, undifferentiated carcinomas, and carcinosarcomas. FIGO grade 3 endometrioid carcinoma is diagnosed when an endometrioid carcinoma exhibits >50% solid architecture (excluding squamous areas), or when an architecturally FIGO grade 2 endometrioid carcinoma exhibits marked cytologic atypia, provided that a glandular variant of serous carcinoma has been excluded. The most useful immunohistochemical studies to make the distinction between these 2 histotypes are p53, p16, DNA mismatch repair proteins, PTEN, and ARID1A. Endometrial clear cell carcinomas must display prototypical architectural and cytologic features for diagnosis. Immunohistochemical stains, including, Napsin A and p504s can be used as ancillary diagnostic tools; p53 expression is aberrant in a minority of clear cell carcinomas. Of note, clear cells are found in all types of high-grade endometrial carcinomas, leading to a tendency to overdiagnose clear cell carcinoma. Undifferentiated carcinoma (which when associated with a component of low-grade endometrioid carcinoma is termed "dedifferentiated carcinoma") is composed of sheets of monotonous, typically dyscohesive cells, which can have a rhabdoid appearance; they often exhibit limited expression of cytokeratins and epithelial membrane antigen, are usually negative for PAX8 and hormone receptors, lack membranous e-cadherin and commonly demonstrate loss of expression of DNA mismatch repair proteins and SWI-SNF chromatin remodeling proteins. Carcinosarcomas must show unequivocal morphologic evidence of malignant epithelial and mesenchymal differentiation.

Dedifferentiated endometrial carcinoma is an aggressive type of endometrial cancer that contains a mix of low-grade endometrioid and undifferentiated carcinoma components. We performed targeted sequencing of eight dedifferentiated carcinomas and identified somatic frameshift/nonsense mutations in SMARCA4, a core ATPase of the switch/sucrose non-fermenting (SWI/SNF) complex, in the undifferentiated components of four tumors. Immunohistochemical analysis confirmed the loss of SMARCA4 in the undifferentiated component of these four SMARCA4-mutated cases, whereas the corresponding low-grade endometrioid component showed retained SMARCA4 expression. An expanded survey of other members of the SWI/SNF complex showed SMARCB1 loss in the undifferentiated component of two SMARCA4-intact tumors, and all SMARCA4- or SMARCB1-deficient tumors showed concomitant loss of expression of SMARCA2. We subsequently examined the expression of SMARCA2, SMARCA4, and SMARCB1 in an additional set of 22 centrally reviewed dedifferentiated carcinomas and 31 grade 3 endometrioid carcinomas. Combining the results from the index and the expansion set, 15 of 30 (50%) of the dedifferentiated carcinomas examined showed either concurrent SMARCA4 and SMARCA2 loss (37%) or concurrent SMARCB1 and SMARCA2 loss (13%) in the undifferentiated component. The loss of SMARCA4 or SMARCB1 was mutually exclusive. All 31 grade 3 endometrioid carcinomas showed intact expression of these core SWI/SNF proteins. The majority (73%) of the SMARCA4/SMARCA2-deficient and half of SMARCB1/SMARCA2-deficient undifferentiated component developed in a mismatch repair-deficient molecular context. The observed spatial association between SWI/SNF protein loss and histologic dedifferentiation suggests that inactivation of these core SWI/SNF proteins may contribute to the development of dedifferentiated endometrial carcinoma.

Endometrioid, serous, and clear cell carcinomas are the major types of endometrial carcinoma. Histologic distinction between these different tumor types can be difficult in high-grade cases, in which significant interobserver diagnostic disagreement exists. Endometrioid and clear cell carcinomas frequently harbor ARID1A and/or PTEN mutations. Serous carcinoma acquires TP53 mutations/inactivation at onset, with a significant subset harboring an additional mutation in PPP2R1A. This study examines the correlation between tumor histotype and genotype in 36 previously genotyped high-grade endometrial carcinomas. This included 23 endometrioid/clear cell genotype and 13 serous genotype tumors. Eight subspecialty pathologists reviewed representative online slides and rendered diagnoses before and after receiving p53, p16, and estrogen receptor immunostaining results. κ statistics for histotype-genotype concordance were calculated. The average κ values for histotype-genotype concordance was 0.55 (range, 0.30 to 0.67) on the basis of morphologic evaluation alone and it improved to 0.68 (range, 0.54 to 0.81) after immunophenotype consideration (P<0.001). Genotype-incompatible diagnoses were rendered by at least 2 pathologists in 12 of 36 cases (33%) (3 cases by 2/8 pathologists, 2 by 3/8, 2 by 4/8, 3 by 6/8, 1 by 7/8, and 1 case by 8/8 pathologists). Six of the 12 were endometrioid/clear cell genotype tumors, and the other 6 were serous genotype tumors. The histopathologic features associated with histotype-genotype-discordant cases were reviewed, and specific diagnostic recommendations were made to improve concordance. This study found that although the majority of morphologic diagnoses are genotype concordant, genotype-incompatible diagnoses are made in a significant subset of cases. Judicious use and interpretation of p53 immunohistochemistry in selected scenarios can improve histotype-genotype concordance.

A subset of endometrial stromal sarcoma harbors t(10;17)(q23;p13), which results in the genetic fusion between YWHAE and 1 of 2 highly homologous FAM22 family members-FAM22A or FAM22B. In contrast to classic low-grade endometrial stromal sarcoma with JAZF1-SUZ12 fusions, YWHAE-FAM22 endometrial stromal sarcoma displays high-grade histologic features and is associated with more aggressive disease course. Ancillary fluorescence in situ hybridization assay demonstrating the presence of YWHAE rearrangement can be used to support the diagnosis, but the detection of fusion transcript would be the most definitive test. We describe here an optimized reverse transcription-polymerase chain reaction assay for detection of YWHAE-FAM22 fusion transcript in formalin-fixed and paraffin-embedded tumor samples. We studied a series of 6 YWHAE-FAM22 endometrial stromal sarcomas, 7 JAZF-SUZ12 endometrial stromal sarcomas, 3 JAZF1-PHF1/EPC1-PHF1 endometrial stromal sarcomas, 6 undifferentiated endometrial sarcomas, 4 uterine leiomyosarcomas, and 4 uterine adenosarcomas. All 6 YWHAE-FAM22 endometrial stromal sarcomas were confirmed by fluorescence in situ hybridization assay, whereas all non-YWHAE-FAM22 tumors were confirmed to lack YWHAE rearrangement by fluorescence in situ hybridization assay. The reverse transcription-polymerase chain reaction assay optimized for formalin-fixed and paraffin-embedded samples detected YWHAE-FAM22 fusion transcripts in all 6 YWHAE-FAM22 endometrial stromal sarcomas and none of the 24 non-YWHAE-FAM22 uterine sarcomas. These findings show that this reverse transcription-polymerase chain reaction assay is sensitive and specific for detection of YWHAE-FAM22 fusion transcript and can serve as a useful adjunct diagnostic assay to confirm the diagnosis of YWHAE-FAM22 endometrial stromal sarcoma in formalin-fixed and paraffin-embedded tumor samples., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The purposes of this study are to assess the level of interobserver variability in the diagnosis of endometrial carcinomas with clear cells by gynecologic pathologists based purely on their morphologic features and to comparatively describe the cases of putative clear cell carcinoma (CCC) with and without significant interobserver variability. A total of 35 endometrial carcinomas (1 slide per case) were reviewed by 11 gynecologic pathologists (median experience: 10 y) from 11 North American institutions. The cases were selected from the files of 3 institutions on the basis of the presence of at least focal clear cells and had previously been classified as a variety of histotypes at these institutions. Diagnoses were rendered in a blinded manner and without predetermined diagnostic criteria or categories. The κ values between any pair of observers ranged from 0.18 to 0.69 (combined 0.46), which was indicative of a "moderate" level of interobserver agreement for the group. Subgroups of "confirmed CCC" [cases diagnosed as such by at least 8 (73%) of the 11 observers, n=14] and "possible CCC" (cases diagnosed as CCC by ≥1 but <8 observers, n=13) were compared with regard to a variety of semiquantified morphologic features. By combining selected morphologic features that displayed statistically significant differences between the 2 groups on univariate analyses, the following approximate morphologic profile emerged for the confirmed CCC group: papillae with hyalinized cores in ≥33% of the lesion, clear cells in ≥33% of the lesion, hyperchromasia in ≥33% of the lesion, the absence of nuclear pseudostratification in >3 cells on the papillae, the absence of nuclear pseudostratification in glands in ≥33% of the lesion, the absence of diffuse grade 3 nuclei, the absence of long and slender papillae in ≥33% of the lesion, and glands and papillae lined by cuboidal to flat, noncolumnar cells. In a backward stepwise logistic regression analysis, features from the profile that predicted the confirmed CCC group included: (1) absence or minimality of diffuse sheets of grade 3 nuclei [P=0.025; 95% confidence interval (CI), 0.0266-0.363]; (2) absence or minimality of nuclear stratification in glands and papillae (P=0.040; 95% CI, -0.228 to -0.0054); and (3) glands and papillae lined by cuboidal to flat, noncolumnar cells (P=0.008; 95% CI, 0.0911-0.566). The 2 groups displayed significant overlap regarding a wide variety of features, and no single case displayed a full complement of potentially diagnostic features. Morphologic patterns associated with cases with very high levels of interobserver variability (defined as cases with ≥4 different diagnoses rendered for them, n=9) included the near-exclusive or exclusively solid pattern of clear cells (3/9) and glandular/papillary proliferations whose only CCC-like feature was the presence of clear cells (2/9). In conclusion, the diagnosis of endometrial carcinomas with clear cells by gynecologic pathologists is associated with a moderate level of interobserver variability. However, there is a morphologic profile that characterizes cases that gynecologic pathologists more uniformly classify as CCC, and the presence of these features is supportive of a CCC diagnosis in an endometrial carcinoma with clear cells. Cases that display broad and significant qualitative deviations from the aforementioned profile should prompt the consideration of a diagnosis other than CCC.