Search

Vulvovaginal melanoma (VVM) is a rare but deadly disease, accounting for 5% of all vulvar malignancies, with a 5-yr survival rate of only 47% for all stages of the disease. VVM is a distinct subset of melanoma, with a unique genomic profile and underlying pathogenesis unassociated with sun exposure. Distinguishing these rare malignancies from very common pigmented lesions of the vulva and vagina is challenging as histologic features often overlap between entities. PReferentially expressed Antigen in MElanoma (PRAME) is a melanoma-associated protein, and immunohistochemistry (IHC) for PRAME distinguishes cutaneous, oral mucosal, and retinal melanoma from atypical nevi. Given the biological differences between VVM and cutaneous melanoma, the utility of PRAME IHC for the diagnosis of VVM is unknown. We accrued a cohort of 20 VVM and 21 benign vulvar melanocytic nevi. We found that nuclear PRAME IHC staining with 4+ intensity was present in 85% of the VVM and 0% of the nevi. With the assistance of PRAME IHC, we found evidence of close or positive margin involvement in 3 of 10 cases where margins were originally diagnosed as negative for melanoma in situ. Our study is the first to assess PRAME IHC in a cohort of VVM cases and provides confidence for using PRAME IHC to assist with diagnosis and margin assessment in this rare disease.

Supplemental Digital Content is available in the text.Uterine tumor resembling ovarian sex cord tumor (UTROSCT) is a rare mesenchymal neoplasm, of uncertain biological potential, that was recently reported to exhibit recurrent gene fusions involving NCOA2-3. The purpose of this study was to, using a larger sample size, better characterize the histopathologic and molecular diversity of UTROSCT. Twenty-six cases of UTROSCT from 5 institutions were selected for further study. Fluorescence in situ hybridization for NCOA1, NCOA2, NCOA3, ESR1and GREB1, and targeted RNA sequencing was performed on 17 and 8 UTROSCTs, respectively. Eight cases underwent massively parallel sequencing to detect single nucleotide variants (SNV), copy number variations, and structural variants using a targeted hybrid-capture based assay. NCOA1-3rearrangement was identified in 81.8% (18/22) of cases. The most common fusion was ESR1-NCOA3, occurring in 40.9% (9/22). GREB1-NCOA1(n=4), ESR1-NCOA2(n=3), and GREB1-NCOA2(n=1) rearrangements were also identified. No recurrent SNVs were identified and no tumor had SNVs in FOXL2, DICER1, STK11, or AKT1, which can be seen in ovarian sex cord-stromal tumors. Copy number variations were infrequent. Clinical follow-up was available for 11 cases with a mean follow-up interval of 94.4 (range, 1 to 319) months. Only one case had a recurrence 66 months after the initial diagnosis and this was the single case with a GREB1-NCOA2fusion. This study reports the morphologic spectrum of UTROSCT and confirms the recently reported recurrent NCOA2-3gene fusions, in addition to identifying novel rearrangements involving NCOA1in these tumors.

Uterine yolk sac tumors have gained increased recognition in recent years. The current study is a multi-faceted examination of yolk sac tumor-like phenotypes in endometrial tumors, based on an analysis of 3 groups of uterine tumors: Group 1: 9 endometrial tumors that had been classified as yolk sac tumor, or as having a yolk sac tumor component, were assessed with a 35-marker immunohistochemical panel, with the goal of defining their immunophenotypic spectrum; Group 2, comprised of 70 endometrial carcinomas of various histotypes, were analyzed for their expression of SALL4, Glypican-3, and AFP, to assess the specificity of these markers for yolk sac tumors relative to endometrial carcinomas; Group 3, comprised of 626 archived cases of endometrial carcinoma/carcinosarcoma, reviewed to define the frequency of yolk sac tumor-like morphology therein. Yolk sac tumor areas in the Group 1 cases were consistently immunoreactive for SALL4 and Glypican-3; variably positive for AFP (89%), Villin (89%), PLAP (78%), 34βE12 (67%), CAM 5.2 (62.5%), EMA (56%), CD117 (50%), p16 (50%), CDX2 (44%), p53 (44% aberrant), MOC31 (37.5%), CK7 (33%), GATA3 (33%), CK5 (25%), and PAX8 (11%); and were negative for CD30, Napsin A, OCT4, estrogen, androgen, and progesterone receptors. 29 (41%) of the 70 group-2 cases expressed at least one of the 3 markers, and 96% of the positive cases was a high-grade histotype. Glypican-3, SALL4, and AFP were positive in 30, 20, and 2.8% of group-2 cases respectively; however, co-expression of any 2, or all 3 markers was uncommon (<9 and 1.4% of cases respectively). Potential yolk sac tumor-like morphology was identified in 5 (0.8%) of 626 group-3 cases, and three were ultimately deemed to be true yolk sac tumor phenotypes based on their morphologic and immunophenotypic similarity to the group 1 cases. These findings highlight the broad immunophenotypic spectrum of uterine yolk sac tumors, the potential pitfalls associated with using immunophenotypes alone to define yolk sac tumor differentiation in endometrial carcinoma, and the utility and limitations of morphologic assessment to identify yolk sac tumors at this site.

Uterine yolk sac tumors have gained increased recognition in recent years. The current study is a multi-faceted examination of yolk sac tumor-like phenotypes in endometrial tumors, based on an analysis of 3 groups of uterine tumors: Group 1: 9 endometrial tumors that had been classified as yolk sac tumor, or as having a yolk sac tumor component, were assessed with a 35-marker immunohistochemical panel, with the goal of defining their immunophenotypic spectrum; Group 2, comprised of 70 endometrial carcinomas of various histotypes, were analyzed for their expression of SALL4, Glypican-3, and AFP, to assess the specificity of these markers for yolk sac tumors relative to endometrial carcinomas; Group 3, comprised of 626 archived cases of endometrial carcinoma/carcinosarcoma, reviewed to define the frequency of yolk sac tumor-like morphology therein. Yolk sac tumor areas in the Group 1 cases were consistently immunoreactive for SALL4 and Glypican-3; variably positive for AFP (89%), Villin (89%), PLAP (78%), 34βE12 (67%), CAM 5.2 (62.5%), EMA (56%), CD117 (50%), p16 (50%), CDX2 (44%), p53 (44% aberrant), MOC31 (37.5%), CK7 (33%), GATA3 (33%), CK5 (25%), and PAX8 (11%); and were negative for CD30, Napsin A, OCT4, estrogen, androgen, and progesterone receptors. 29 (41%) of the 70 group-2 cases expressed at least one of the 3 markers, and 96% of the positive cases was a high-grade histotype. Glypican-3, SALL4, and AFP were positive in 30, 20, and 2.8% of group-2 cases respectively; however, co-expression of any 2, or all 3 markers was uncommon (<9 and 1.4% of cases respectively). Potential yolk sac tumor-like morphology was identified in 5 (0.8%) of 626 group-3 cases, and three were ultimately deemed to be true yolk sac tumor phenotypes based on their morphologic and immunophenotypic similarity to the group 1 cases. These findings highlight the broad immunophenotypic spectrum of uterine yolk sac tumors, the potential pitfalls associated with using immunophenotypes alone to define yolk sac tumor differentiation in endometrial carcinoma, and the utility and limitations of morphologic assessment to identify yolk sac tumors at this site.

Genetic alterations in uterine myxoid leiomyosarcoma are unknown. We investigate the clinicopathologic features of 19 uterine tumors previously diagnosed as myxoid leiomyosarcomas in which tumoral RNA was subjected to targeted RNA sequencing. PLAG1, BCOR, BCORL1, HMGA2, and ALKbreak-apart fluorescence in situ hybridization (FISH) and BCOR, PLAG1, and ALK immunohistochemistry were performed in cases which failed or lacked fusions by sequencing. The diagnosis of myxoid leiomyosarcoma was confirmed in 15 cases after exclusion of 4 tumors with BCORand ALKrearrangements. These 15 patients presented at a median age of 50 years with stage I (3), II (2), III (2), and IV (1) tumors, respectively; stage was unknown in 7 cases. Tumor size ranged from 10 to 24 cm. Matrix was myxoid in all tumors and also eosinophilic in 2. Cells were spindled, epithelioid, and both in 10, 2, and 3 tumors and showed mild, moderate, and severe nuclear atypia in 3, 8, and 4 tumors, respectively. Mitotic index ranged from <1 to 14/10 HPF, while tumor necrosis was present in 6 (40%). Novel TRPS1-PLAG1or RAD51B-PLAG1fusions were detected by sequencing in 4 tumors, 3 of which were also confirmed by FISH. Diffuse PLAG1 expression was seen in 7 tumors, including 4 with PLAG1rearrangement. No morphologic differences were seen among PLAG1fusion-positive and fusion-negative tumors. No PLAG1, HMGA2, ALK, BCOR, or BCORL1rearrangements were detected by FISH in 11 tumors. On the basis of sequencing and FISH results, PLAG1rearrangements resulting in PLAG1 expression underpin ~25% of myxoid leiomyosarcomas and may serve as a useful diagnostic biomarker. Immunohistochemistry, targeted RNA sequencing, and/or FISH may distinguish myxoid leiomyosarcoma from its morphologic mimics.

High-grade endometrial stromal sarcoma likely encompasses underrecognized tumors harboring genetic abnormalities besides YWHAE–NUTM2fusion. Triggered by three initial endometrial stromal sarcomas with ZC3H7B–BCORfusion characterized by high-grade morphology and aggressive clinical behavior, we herein investigate the clinicopathologic features of this genetic subset by expanding the analysis to 17 such tumors. All of them occurred in adult women with a median age of 54 (range, 28–71) years. They were predominantly based in the endomyometrium and demonstrated tongue-like and/or pushing myometrial invasion. Most were uniformly cellular and displayed haphazard fascicles of spindle cells with mild to moderate nuclear atypia. Myxoid matrix was seen in 14 of 17 (82%) tumors, and collagen plaques were seen in 8 (47%). The mitotic index was ≥10 mitotic figures/10 high-power fields (HPFs) in 14 of 17 (82%) tumors with a median of 14.5 mitotic figures/10 HPFs. No foci of conventional or variant low-grade endometrial stromal sarcoma were seen. All tumors expressed CD10 with only limited or absent desmin, SMA and/or h-caldesmon staining. ER and PR expression in >5% of cells was seen in 4 of 12 (33%) tumors. Diffuse cyclin D1 and BCOR immunoreactivity was present in 7 of 8 (88%) and 7 of 14 (50%) tumors, respectively. Fluorescence in situhybridization or targeted RNA sequencing confirmed ZC3H7B–BCORfusion in all tumors, including four and two previously diagnosed as myxoid leiomyosarcoma and undifferentiated uterine sarcoma, respectively. Limited clinical data suggest that patients present at higher stage and have worse prognosis compared with published outcomes in low-grade endometrial stromal sarcoma. Tumors with ZC3H7B–BCORfusion constitute a distinct group of endometrial stromal sarcomas with high-grade morphology that should be distinguished from other uterine mesenchymal neoplasms that may demonstrate myxoid morphology.

High-grade endometrial stromal sarcoma likely encompasses underrecognized tumors harboring genetic abnormalities besides YWHAE–NUTM2fusion. Triggered by three initial endometrial stromal sarcomas with ZC3H7B–BCORfusion characterized by high-grade morphology and aggressive clinical behavior, we herein investigate the clinicopathologic features of this genetic subset by expanding the analysis to 17 such tumors. All of them occurred in adult women with a median age of 54 (range, 28–71) years. They were predominantly based in the endomyometrium and demonstrated tongue-like and/or pushing myometrial invasion. Most were uniformly cellular and displayed haphazard fascicles of spindle cells with mild to moderate nuclear atypia. Myxoid matrix was seen in 14 of 17 (82%) tumors, and collagen plaques were seen in 8 (47%). The mitotic index was ≥10 mitotic figures/10 high-power fields (HPFs) in 14 of 17 (82%) tumors with a median of 14.5 mitotic figures/10 HPFs. No foci of conventional or variant low-grade endometrial stromal sarcoma were seen. All tumors expressed CD10 with only limited or absent desmin, SMA and/or h-caldesmon staining. ER and PR expression in >5% of cells was seen in 4 of 12 (33%) tumors. Diffuse cyclin D1 and BCOR immunoreactivity was present in 7 of 8 (88%) and 7 of 14 (50%) tumors, respectively. Fluorescence in situhybridization or targeted RNA sequencing confirmed ZC3H7B–BCORfusion in all tumors, including four and two previously diagnosed as myxoid leiomyosarcoma and undifferentiated uterine sarcoma, respectively. Limited clinical data suggest that patients present at higher stage and have worse prognosis compared with published outcomes in low-grade endometrial stromal sarcoma. Tumors with ZC3H7B–BCORfusion constitute a distinct group of endometrial stromal sarcomas with high-grade morphology that should be distinguished from other uterine mesenchymal neoplasms that may demonstrate myxoid morphology.

The recent implementation of next generation sequencing and multigene platforms has expanded the spectrum of hereditary breast and ovarian cancer syndrome, beyond the traditional genes BRCA1and BRCA2. A large number of other moderate penetrance genes have now been uncovered, which also play critical roles in repairing double stranded DNA breaks through the homologous recombination pathway. This review discusses the landmark discoveries of BRCA1and BRCA2, the homologous repair pathway and new genes discovered in hereditary breast and ovarian cancer syndrome, as well as their clinicopathologic significance and implications for genetic testing. It also highlights the new role of PARP inhibitors in the context of synthetic lethality and prophylactic surgical options.

Undifferentiated endometrial carcinoma is an aggressive type of endometrial carcinoma that typically presents with advanced stage disease and rapid clinical progression. In contrast to dedifferentiated endometrial carcinoma, undifferentiated carcinoma lacks a concurrent differentiated (typically low-grade endometrioid) carcinoma component, though the undifferentiated component of dedifferentiated carcinoma is similar histologically and immunophenotypically to pure undifferentiated carcinoma. We recently identified 3 mutually exclusive mechanisms of switch/sucrose nonfermentable (SWI/SNF) complex inactivation (BRG1 inactivation, INI1 inactivation or ARID1A/ARID1B co-inactivation) that are associated with histologic dedifferentiation in the majority of dedifferentiated endometrial carcinoma. In the current study, we aimed to determine by immunohistochemistry whether these patterns of SWI/SNF inactivation also occur in undifferentiated endometrial carcinomas. Of the 34 undifferentiated carcinomas examined, 17 (50%) exhibited SWI/SNF complex inactivation, with 11 tumors showing complete loss of both ARID1A and ARID1B, 5 showing complete loss of BRG1 and 1 showing complete loss of INI1. Ten of the remaining 17 undifferentiated carcinomas showed the following alterations: 5 tumors (15%) showed loss of ARID1A only with intact ARID1B, BRG1, and INI1 expression, 4 tumors (12%) showed mutated patterns of p53 staining with intact SWI/SNF protein expression, and 1 tumor (3%) harbored a POLEexonuclease domain mutation (P286R). SWI/SNF complex-inactivated tumors presented more frequently with extrauterine disease spread than those with intact expression (88% vs. 41%, respectively). In addition, patients with SWI/SNF complex-inactivated tumors had a significantly worse disease-specific survival (P=0.02). The findings here demonstrate frequent SWI/SNF complex inactivation in undifferentiated endometrial carcinomas, which has future implications regarding therapies that target chromatin remodelling and epigenetic control.

Mixed endometrioid and clear cell carcinoma of the endometrium refers to a scenario in which the tumor exhibits histologic features of both endometrioid and clear cell carcinoma. We observed a tendency for these tumors to occur in a mismatch repair (MMR) protein-deficient molecular background in a prior study that examined a small cohort of mixed-type endometrial carcinomas. The aim of this study was to determine the rate of MMR protein deficiency in a larger series of endometrial mixed endometrioid and clear cell carcinomas, through a retrospective survey of MLH1, PMS2, MSH2, and MSH6 expression in such tumors at 5 tertiary centers. A total of 41 cases were identified and 27 (66%) tumors demonstrated MMR protein deficiency with a comparable frequency across the contributing centers (ranging from 56% to 83%). Among the MMR protein-deficient cases, 59% showed concurrent MLH1 and PMS2 loss, 33% showed concurrent MSH2 and MSH6 loss, and 4% showed isolated PMS2 or MSH6 loss. Compared with a previously published series of 15 pure endometrial clear cell carcinomas, mixed endometrioid and clear cell carcinomas are associated with significantly better disease-specific survival (P=0.02). In summary, endometrial carcinomas with mixed endometrioid and clear cell histology are frequently MMR protein deficient. This finding has implications both for our understanding of its tumor biology and for the identification of patients with potential Lynch syndrome.

Recognition of high-grade endometrial stromal sarcoma is important because of its aggressive clinical behavior. Morphologic features of YWHAE-NUTM2 high-grade endometrial stromal sarcoma may overlap with other uterine sarcoma types. BCOR immunoexpression was studied in these tumors and their morphologic mimics to assess its diagnostic utility. BCOR immunohistochemical staining was performed on archival tissue from 28 high-grade endometrial stromal sarcomas with classic morphology (20 YWHAE-NUTM2, 5 ZC3H7B-BCOR, 3 BCOR-ZC3H7B), 3 high-grade endometrial stromal sarcomas with unusual morphology and unknown gene rearrangement status, 66 low-grade endometrial stromal sarcomas, 21 endometrial stromal nodules, 38 uterine leiomyosarcomas, and 19 uterine leiomyomas. Intensity of nuclear staining and percentage of positive tumor cells were recorded. Strong diffuse nuclear BCOR staining (defined as >95% of tumor cells) was seen in the round cell component of all 20 (100%) classic YWHAE-NUTM2 high-grade endometrial stromal sarcomas and the 3 unusual high-grade endometrial stromal sarcomas which prompted FISH studies confirming YWHAE rearrangement in 2 tumors. Genomic PCR confirmed the presence of BCOR exon 16 internal tandem duplication in the third case. Diffuse BCOR staining was strong in three and weak in one BCOR-rearranged high-grade endometrial stromal sarcoma while absent in the remaining four BCOR-rearranged tumors. BCOR staining was weakly positive in <5% of tumor cells in 4 of 66 (6%) low-grade endometrial stromal sarcomas and 1 of 18 (6%) endometrial stromal nodules and weakly to moderately positive in <5–40% of tumor cells in 6 of 31 (19%) leiomyosarcomas. No BCOR staining was seen in the remaining low-grade endometrial stromal sarcomas, endometrial stromal nodules, leiomyosarcomas, or any of the leiomyomas. BCOR immunohistochemical staining is a highly sensitive marker for YWHAE-NUTM2 high-grade endometrial stromal sarcoma with both classic and unusual morphology and identifies a subset of high-grade endometrial stromal sarcoma with BCOR alterations, including BCOR rearrangement and internal tandem duplication.

Recognition of high-grade endometrial stromal sarcoma is important because of its aggressive clinical behavior. Morphologic features of YWHAE-NUTM2high-grade endometrial stromal sarcoma may overlap with other uterine sarcoma types. BCOR immunoexpression was studied in these tumors and their morphologic mimics to assess its diagnostic utility. BCOR immunohistochemical staining was performed on archival tissue from 28 high-grade endometrial stromal sarcomas with classic morphology (20 YWHAE-NUTM2, 5 ZC3H7B-BCOR, 3 BCOR-ZC3H7B), 3 high-grade endometrial stromal sarcomas with unusual morphology and unknown gene rearrangement status, 66 low-grade endometrial stromal sarcomas, 21 endometrial stromal nodules, 38 uterine leiomyosarcomas, and 19 uterine leiomyomas. Intensity of nuclear staining and percentage of positive tumor cells were recorded. Strong diffuse nuclear BCOR staining (defined as >95% of tumor cells) was seen in the round cell component of all 20 (100%) classic YWHAE-NUTM2high-grade endometrial stromal sarcomas and the 3 unusual high-grade endometrial stromal sarcomas which prompted FISH studies confirming YWHAErearrangement in 2 tumors. Genomic PCR confirmed the presence of BCORexon 16 internal tandem duplication in the third case. Diffuse BCOR staining was strong in three and weak in one BCOR-rearranged high-grade endometrial stromal sarcoma while absent in the remaining four BCOR-rearranged tumors. BCOR staining was weakly positive in <5% of tumor cells in 4 of 66 (6%) low-grade endometrial stromal sarcomas and 1 of 18 (6%) endometrial stromal nodules and weakly to moderately positive in <5–40% of tumor cells in 6 of 31 (19%) leiomyosarcomas. No BCOR staining was seen in the remaining low-grade endometrial stromal sarcomas, endometrial stromal nodules, leiomyosarcomas, or any of the leiomyomas. BCOR immunohistochemical staining is a highly sensitive marker for YWHAE-NUTM2high-grade endometrial stromal sarcoma with both classic and unusual morphology and identifies a subset of high-grade endometrial stromal sarcoma with BCORalterations, including BCORrearrangement and internal tandem duplication.

The Cancer Genome Atlas recently identified a genomic-based molecular classification of endometrial carcinomas, with 4 molecular categories: (1) ultramutated (polymerase epsilon [POLE] mutated), (2) hypermutated (microsatellite instability), (3) copy number abnormalities-low, and (4) copy number abnormalities-high. Two studies have since proposed models to classify endometrial carcinomas into 4 molecular subgroups, modeled after The Cancer Genome Atlas, using simplified and more clinically applicable surrogate methodologies. In our study, 151 endometrial carcinomas were molecularly categorized using sequencing for the exonuclease domain mutations (EDM) of POLE, and immunohistochemistry for p53 and mismatch repair (MMR) proteins. This separated cases into 1 of 4 groups: (1) POLEEDM, (2) MMR-D, (3) p53 wildtype (p53 wt), or (4) p53 abnormal (p53 abn). Seven gynecologic pathologists were asked to assign each case to one of the following categories: grade 1 to 2 endometrioid carcinoma (EC), grade 3 EC, mucinous, serous carcinoma (SC), clear cell, dedifferentiated, carcinosarcoma, mixed, and other. Consensus diagnosis among all 7 pathologists was highest in the p53 wt group (37/41, 90%), lowest in the p53 abn group (14/36, 39%), and intermediate in the POLEEDM (22/34, 65%) and MMR-D groups (23/40, 58%). Although the majority of p53 wt endometrial carcinomas are grade 1 to 2 EC (sensitivity: 90%), fewer than half of grade 1 to 2 EC fell into the p53 wt category (positive predictive value: 42%). Pure SC almost always resided in the p53 abn group (positive predictive value: 96%), but it was insensitive as a marker of p53 abn (sensitivity 64%) and the reproducibility of diagnosing SC was suboptimal. The limitations in the precise histologic classification of endometrial carcinomas highlights the importance of an ancillary molecular-based classification scheme.

Endometrial stromal sarcomas (ESS) are often underpinned by recurrent chromosomal translocations resulting in the fusion of genes involved in epigenetic regulation. To date, only YWHAE-NUTM2rearrangements are associated with distinctive high-grade morphology and aggressive clinical behavior. We identified 3 ESS morphologically mimicking myxoid leiomyosarcoma of the uterus and sought to describe their unique histopathologic features and identify genetic alterations using next-generation sequencing. All cases displayed predominantly spindled cells associated with abundant myxoid stroma and brisk mitotic activity. Tumors involved the endometrium and demonstrated tongue-like myometrial infiltration. All 3 were associated with an aggressive clinical course, including multisite bony metastases in 1 patient, progressive peritoneal disease after chemotherapy in another, and metastases to the lung and skin in the last patient. All 3 ESS were found to harbor ZC3H7B-BCORgene fusions by targeted sequencing and fluorescence in situ hybridization. On the basis of the review of these cases, we find that ESS with ZC3H7B-BCORfusion constitutes a novel type of high-grade ESS and shares significant morphologic overlap with myxoid leiomyosarcoma.

Dedifferentiated carcinoma of the endometrium or the ovary is an aggressive epithelial malignancy that comprises an endometrioid carcinoma together with an undifferentiated carcinoma. We recently reported that inactivation of BRG1 or INI1, core subunits of the switch/sucrose non-fermenting (SWI/SNF) complex, was the likely molecular event underlying dedifferentiation in about half of dedifferentiated carcinomas. In this study, we performed a genomic screen that included other members of the SWI/SNF complex to better delineate the molecular basis in the remainder of these tumours. We identified concurrent inactivating mutations involving ARID1A and ARID1B in 12 of 24 BRG1/INI1-intact, 0 of 3 INI1-deficient and 0 of 16 BRG1-deficient dedifferentiated carcinomas. All ARID1A and ARID1B co-mutated tumours displayed loss of ARID1A expression in the undifferentiated component with 11 of 12 tumours also displaying absent staining in the endometrioid component. ARID1B expression was absent in the undifferentiated component in all 12 tumours, whereas the corresponding endometrioid component showed intact expression. Clinically, ARID1A/ARID1B co-inactivated tumours showed similar aggressive behaviour to BRG1 or INI1-inactivated tumours. Given that ARID1A and ARID1B are the only known DNA-binding subunits of the SWI/SNF-A complex, additional inactivation of ARID1B in an ARID1A-deficient background appears to represent an alternative mechanism of disruption of SWI/SNF-mediated transcriptional regulation, resulting in arrested cellular differentiation in endometrial and ovarian endometrioid cancer.

Dedifferentiated carcinoma of the endometrium or the ovary is an aggressive epithelial malignancy that comprises an endometrioid carcinoma together with an undifferentiated carcinoma. We recently reported that inactivation of BRG1 or INI1, core subunits of the switch/sucrose non-fermenting (SWI/SNF) complex, was the likely molecular event underlying dedifferentiation in about half of dedifferentiated carcinomas. In this study, we performed a genomic screen that included other members of the SWI/SNF complex to better delineate the molecular basis in the remainder of these tumours. We identified concurrent inactivating mutations involving ARID1Aand ARID1Bin 12 of 24 BRG1/INI1-intact, 0 of 3 INI1-deficient and 0 of 16 BRG1-deficient dedifferentiated carcinomas. All ARID1Aand ARID1Bco-mutated tumours displayed loss of ARID1A expression in the undifferentiated component with 11 of 12 tumours also displaying absent staining in the endometrioid component. ARID1B expression was absent in the undifferentiated component in all 12 tumours, whereas the corresponding endometrioid component showed intact expression. Clinically, ARID1A/ARID1B co-inactivated tumours showed similar aggressive behaviour to BRG1 or INI1-inactivated tumours. Given that ARID1A and ARID1B are the only known DNA-binding subunits of the SWI/SNF-A complex, additional inactivation of ARID1B in an ARID1A-deficient background appears to represent an alternative mechanism of disruption of SWI/SNF-mediated transcriptional regulation, resulting in arrested cellular differentiation in endometrial and ovarian endometrioid cancer.

Small cell carcinomas of the ovary, hypercalcemic type, are exceptionally rare yet aggressive tumors, typically affecting young women in the second to third decades of life. Less than half of patients survive beyond 2 years of the diagnosis, even with early stage disease and aggressive multimodal therapy. Here, we present a case of small cell carcinoma of the ovary, hypercalcemic type, occurring in a 19-year-old woman and review the historical aspects, clinical features, histopathology, treatment, recent molecular discoveries, and future therapeutic prospects in this rare tumor type.

Growing evidence has established two major types of vulvar intraepithelial neoplasia (VIN), which correspond to two distinct oncogenic pathways to vulvar squamous cell carcinoma (VSCC). While the incidence of VSCC has remained relatively stable over the last three decades, the incidence of VIN has increased. VIN of usual type (uVIN) is human papillomavirus (HPV)-driven, affects younger women and is a multicentric disease. In contrast, VIN of differentiated type (dVIN) occurs in post-menopausal women and develops independent of HPV infection. dVIN often arises in a background of lichen sclerosus and chronic inflammatory dermatoses. Although isolated dVIN is significantly less common than uVIN, dVIN bears a greater risk for malignant transformation to VSCC and progresses over a shorter time interval. On histological examination, uVIN displays conspicuous architectural and cytological abnormalities, while the morphological features that characterise dVIN are much more subtle and raise a wide differential diagnosis. On the molecular level, dVIN is characterised by a higher number of somatic mutations, particularly in TP53. Here we review the classification, epidemiology, clinical features, histomorphology, ancillary markers and molecular genetics of both types of VIN, and discuss the morphological challenges faced by pathologists in interpreting these lesions.

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.

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.

Mixed endometrial carcinoma refers to a tumor that comprises 2 or more distinct histotypes. We studied 18 mixed-type endometrial carcinomas—11 mixed serous and low-grade endometrioid carcinomas (SC/EC), 5 mixed clear cell and low-grade ECs (CCC/EC), and 2 mixed CCC and SCs (CCC/SC), using targeted next-generation sequencing and immunohistochemistry to compare the molecular profiles of the different histotypes present in each case. In 16 of 18 cases there was molecular evidence that both components shared a clonal origin. Eight cases (6 EC/SC, 1 EC/CCC, and 1 SC/CCC) showed an SC molecular profile that was the same in both components. Five cases (3 CCC/EC and 2 SC/EC) showed a shared endometrioid molecular profile and identical mismatch-repair protein deficiency in both components. A single SC/EC case harbored the same POLEexonuclease domain mutation in both components. One SC/CCC and 1 EC/CCC case showed both shared and unique molecular features in the 2 histotype components, suggesting early molecular divergence from a common clonal origin. In 2 cases, there were no shared molecular features, and these appear to be biologically unrelated synchronous tumors. Overall, these results show that the different histologic components in mixed endometrial carcinomas typically share the same molecular aberrations. Mixed endometrial carcinomas most commonly occur through morphologic mimicry, whereby tumors with serous-type molecular profile show morphologic features of EC or CCC, or through underlying deficiency in DNA nucleotide repair, with resulting rapid accrual of mutations and intratumoral phenotypic heterogeneity. Less commonly, mixed endometrial carcinomas are the result of early molecular divergence from a common progenitor clone or are synchronous biologically unrelated tumors (collision tumors).

Uterine sarcomas and carcinosarcomas are an aggressive group of uterine malignancies. The frequency of mismatch repair (MMR) protein loss by immunohistochemical evaluation has not been comprehensively characterized in this group of tumors; hence, the appropriateness of applying an immunohistochemical panel to screen for Lynch syndrome in these tumors remains unclear. We examined for the immunohistochemical loss of 4 MMR proteins (MLH1, MSH2, MSH6, and PMS2) in a series of 67 uterine carcinosarcomas and 51 uterine sarcomas (20 leiomyosarcomas, 11 adenosarcomas, 9 low-grade endometrial stromal sarcomas, 8 high-grade endometrial stromal sarcomasundifferentiated endometrial sarcomas, and 3 rhabdomyosarcomas) at our institution. Four of the 67 (6.0) carcinosarcomas demonstrated abnormal MMR protein expression. Two tumors showed concurrent loss of MLH1 and PMS2 in both the carcinomatous and sarcomatous components. One tumor showed the loss of only PMS2 in both components. The remaining tumor showed an isolated loss of MLH1 and PMS2 in only the small cell carcinoma component, whereas the non-small-cell carcinoma and sarcoma components demonstrated normal staining patterns for MMR proteins. Two of 20 leiomyosarcomas (10) showed the loss of MMR proteins: one with loss of PMS2 and the other with loss of MSH2 and MSH6. All other uterine sarcoma types examined showed intact MMR protein expression. These observations provide a basis for MMR protein screening in uterine carcinosarcomas and leiomyosarcomas but not in other types of uterine mesenchymal or mixed epithelialmesenchymal malignancies.

Endometrial stromal sarcomas with the YWHAE-NUTM2A/B genetic fusion characteristically contain high-grade round to epithelioid cell component that is strongly and diffusely cyclin D1-positive and it may or may not show an associated low-grade fibroblastic/myxoid cell component. They are clinically more aggressive than endometrial stromal sarcomas with the JAZF1-SUZ12 genetic fusion and frequently demonstrate extrauterine extension at initial clinical presentation. In this setting, the tumor may be misdiagnosed as gastrointestinal stromal tumor. This study examines the expression of KIT and ANO1 in 14 YWHAE-NUTM2A/B tumors by immunohistochemistry. Staining localization was determined as membranous and/or cytoplasmic, and the staining intensity was assessed (negative, weak, moderate and strong). Of the 14 tumors, 6 contained only a high-grade round cell component, 2 only a low-grade fibroblastic component and 6 had both components in the slides evaluated. The high-grade round cell component displayed moderate to strong membranous/cytoplasmic KIT staining in all tumors (12 of 12). The low-grade fibroblastic cell component showed only weak cytoplasmic KIT staining in 3 of 8 tumors. In contrast, ANO1 was negative in all 14 neoplasms, irrespective of the component evaluated. Sanger sequencing analysis (exons 9, 11, 13 and 17) and Ampliseq Cancer Panel mutation screen (Ion Torrent) demonstrated no KIT mutations in three KIT-positive YWHAE-NUTM2A/B tumors. This study shows that the high-grade round cell component of YWHAE-NUTM2A/B endometrial stromal sarcoma consistently expresses KIT but lacks KIT hotspot mutations. KIT expression may represent a potential diagnostic pitfall in the evaluation of YWHAE-NUTM2A/B endometrial stromal sarcoma presenting with pelvic/abdominal mass, particularly in situations where its uterine origin is not definitive, and thus a panel of antibodies that includes ANO1 and cyclin D1 is necessary.

Endometrial stromal sarcomas with the YWHAE-NUTM2A/Bgenetic fusion characteristically contain high-grade round to epithelioid cell component that is strongly and diffusely cyclin D1-positive and it may or may not show an associated low-grade fibroblastic/myxoid cell component. They are clinically more aggressive than endometrial stromal sarcomas with the JAZF1-SUZ12genetic fusion and frequently demonstrate extrauterine extension at initial clinical presentation. In this setting, the tumor may be misdiagnosed as gastrointestinal stromal tumor. This study examines the expression of KIT and ANO1 in 14 YWHAE-NUTM2A/Btumors by immunohistochemistry. Staining localization was determined as membranous and/or cytoplasmic, and the staining intensity was assessed (negative, weak, moderate and strong). Of the 14 tumors, 6 contained only a high-grade round cell component, 2 only a low-grade fibroblastic component and 6 had both components in the slides evaluated. The high-grade round cell component displayed moderate to strong membranous/cytoplasmic KIT staining in all tumors (12 of 12). The low-grade fibroblastic cell component showed only weak cytoplasmic KIT staining in 3 of 8 tumors. In contrast, ANO1 was negative in all 14 neoplasms, irrespective of the component evaluated. Sanger sequencing analysis (exons 9, 11, 13 and 17) and Ampliseq Cancer Panel mutation screen (Ion Torrent) demonstrated no KITmutations in three KIT-positive YWHAE-NUTM2A/Btumors. This study shows that the high-grade round cell component of YWHAE-NUTM2A/Bendometrial stromal sarcoma consistently expresses KIT but lacks KIThotspot mutations. KIT expression may represent a potential diagnostic pitfall in the evaluation of YWHAE-NUTM2A/Bendometrial stromal sarcoma presenting with pelvic/abdominal mass, particularly in situations where its uterine origin is not definitive, and thus a panel of antibodies that includes ANO1 and cyclin D1 is necessary.

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 ARID1Aandor PTENmutations. Serous carcinoma acquires TP53mutationsinactivation 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 endometrioidclear 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. statistics for histotype-genotype concordance were calculated. The average 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 28 pathologists, 2 by 38, 2 by 48, 3 by 68, 1 by 78, and 1 case by 88 pathologists). Six of the 12 were endometrioidclear 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.