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.

Detection of FOXL2 C134W Mutation Status by a Novel BaseScope In Situ Hybridization Assay is Highly Sensitive and Specific for Adult Granulosa Cell Tumors.

Adult granulosa cell tumors (AGCTs) are a molecularly distinct group of malignant ovarian sex cord-stromal tumors (SCSTs) characterized by a nearly ubiquitous c.402C>G/p.C134W mutation in FOXL2 (hereafter referred to as "C134W"). In some cases, AGCT exhibits marked morphologic overlap with other SCSTs and has an identical immunophenotype, and molecular testing may be necessary to help confirm the diagnosis. However, molecular testing is time consuming, relatively expensive, and unavailable in many pathology laboratories. We describe the development and validation of an in situ hybridization (ISH) custom BaseScope assay for the detection of the FOXL2 C134W mutation. We evaluated 106 ovarian SCSTs, including 78 AGCTs, 9 juvenile granulosa cell tumors, 18 fibromas (cellular and conventional), and 1 SCST, not otherwise specified, as well as 53 epithelial ovarian tumors (42 endometrioid carcinomas and 11 carcinosarcomas) and 1 STK11 adnexal tumor for the presence or absence of FOXL2 wild-type and FOXL2 C134W RNA expression via BaseScope-ISH. Fifty-one tumors had previously undergone DNA sequencing of the FOXL2 gene. Across the entire cohort, the FOXL2 C134W probe staining was positive in 77 of 78 (98.7%) AGCTs. Two of 81 (2.5%) non-AGCTs also showed positive staining, both of which were epithelial ovarian tumors. The assay worked in tissue from blocks >20 years old. There was 100% concordance between the FOXL2 sequencing and BaseScope-ISH results. Overall, assessment of FOXL2 mutation status by custom BaseScope-ISH demonstrated 98.7% sensitivity and 97.5% specificity for the diagnosis of AGCT. BaseScope-ISH for FOXL2 C134W represents a reasonable alternative to sequencing, is quicker and less expensive, and is more easily incorporated than molecular testing into many pathology laboratories. It also has the advantage of requiring less tissue, and the neoplastic cells can be directly visualized on stained sections.

High-Grade Endometrial Stromal Sarcomas With YWHAE::NUTM2 Gene Fusion Exhibit Recurrent CDKN2A Alterations and Absence of p16 Staining is a Poor Prognostic Marker.

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.

TSC2-mutant uterine sarcomas with JAZF1-SUZ12 fusions demonstrate hybrid features of endometrial stromal sarcoma and PEComa and are responsive to mTOR inhibition.

Uterine perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm that occasionally shares morphologic and immunohistochemical overlap with low- and high-grade endometrial stromal sarcoma (LGESS and HGESS). In this study, we sought to characterize the clinical, morphologic, genetic, and epigenetic features of five uterine sarcomas that display histologic features of LGESS, HGESS, and PEComa. All tumors demonstrated epithelioid cells often associated with a low-grade spindled component resembling LGESS, with both regions expressing CD10, ER, PR, variable HMB45, and Melan-A immunoreactivity, and strong cathepsin K and pS6 expression. Targeted massively parallel sequencing analysis revealed the presence of somatic TSC2 mutations in all five cases, of which four harbored concurrent or consecutive JAZF1-SUZ12 gene fusions. Unsupervised hierarchical clustering analysis of methylation profiles of TSC2-mutant uterine sarcomas (n = 4), LGESS (n = 10), and HGESS (n = 12) demonstrated two clusters consisting of (1) all LGESS and TSC2-mutant uterine sarcomas and (2) all HGESS. KEGG pathway analysis detected methylation differences in genes involved in PI3K/AKT, calcium, and Rap1 signaling. TSC2-mutant uterine sarcomas were responsive to hormone suppression, and mTOR inhibition demonstrated clinical benefit in four patients with these neoplasms. Our results suggest that these tumors represent histologically distinctive LGESS with TSC2 mutations. TSC2 mutations and JAZF1-SUZ12 fusion may help diagnose these tumors and possibly direct effective treatment.

Endometrial neuroendocrine carcinoma and undifferentiated carcinoma are distinct entities with overlap in neuroendocrine marker expression.

AIMS: Dedifferentiated endometrial carcinomas (DDECs)/undifferentiated endometrial carcinomas (UDECs) frequently harbour genomic activation of switch/sucrose non-fermentable (SWI/SNF)-complex proteins, and can show histological overlap with neuroendocrine carcinoma (NEC). The aim of this study was to compare the extent of the expression of neuroendocrine markers, SWI/SNF proteins and mismatch repair (MMR) proteins in DDEC/UDEC and NEC. METHODS AND RESULTS: The extent of expression of synaptophysin, chromogranin, CD56, ARID1A, ARID1B, SMARCA4, SMARCB1 and MMR proteins was evaluated by immunohistochemistry on 44 SWI/SNF-deficient DDECs/UDECs and 15 NECs. Thirty-three of 44 (75%) DDECs/UDECs showed expression of at least one neuroendocrine marker, with 18 of 44 (41%) expressing two or more neuroendocrine markers, whereas all 15 NECs showed expression of at least one neuroendocrine marker, with 14 of 15 (93%) expressing two or more neuroendocrine markers. Neuroendocrine marker expression in DDECs/UDECs was typically focal when present, with average extents of 17%, 4% and 8% for synaptophysin, chromogranin and CD56 in the positive cases, respectively, in contrast to 73%, 40% and 62% in the positive NEC cases, respectively. All 15 NECs showed intact expression of SWI/SNF-complex proteins, except for one that showed isolated loss of ARID1A. Thirty-eight of 44 DDECs/UDECs were MMR-abnormal (34 with loss of MLH1 and PMS2, and four with loss of PMS2 alone), whereas all NECs retained MMR protein expression. CONCLUSIONS: Our study demonstrates frequent but typically focal neuroendocrine marker expression in SWI/SNF-deficient DDECs/UDECs, whereas NECs typically express two or more neuroendocrine markers, with diffuse expression of at least one marker. ARID1B, SMARCA4 and SMARCB1 immunohistochemistry can be used to aid in the differentiation between DDEC/UDEC and NEC.

Bronchus-like Structures in Ovarian Teratomas: Report of a Series of a Previously Unreported Phenomenon With Potential For Misdiagnosis.

We report 10 cases of a previously undescribed lesion within ovarian teratomas which we designate bronchus-like structures. The lesions occurred in patients aged 16 to 56 yr (mean: 36) and involved the left ovary (n=5) or right ovary (n=5). Nine cases were mature teratomas (dermoid cysts/mature cystic teratomas or mature solid teratomas), 1 with somatic malignant transformation, and 1 was an immature teratoma. The bronchus-like structures ranged in size from 2.5 to 10 mm and were unifocal (7 cases) or multifocal (3 cases). The morphology was relatively constant in all cases and characterised by a well-formed bronchus surrounded by glandular structures, some of which were dilated, separated by stroma containing a variable amount of smooth muscle. In all but 1 case, a proportion of the glands contained abundant foamy cytoplasm. There was little or no nuclear atypia or mitotic activity. At low-power, the glands often had a somewhat "infiltrative" appearance and one case was originally diagnosed as a "pulmonary-type" adenocarcinoma arising in a dermoid cyst. In all cases, there was diffuse staining of the bronchus and glands with TTF1 and Napsin A, confirming the cell lineage. Follow-up in 4 cases (18-130 mo; median: 64 mo) showed no evidence of recurrence; 1 patient died from an unrelated malignancy. In reporting this apparently rare but possibly underrecognized benign lesion arising within ovarian teratomas, we discuss the differential diagnosis and stress that pathologists should be aware of this phenomenon in order to avoid an erroneous diagnosis of malignancy.

An Unusual Enteric Yolk Sac Tumor: First Report of an Ovarian Germ Cell Tumor Associated With a Germline Pathogenic Variant in DICER1.

A variety of unusual tumors are associated with both germline and somatic DICER1 pathogenic variants (PVs), including, in the female genital tract, embryonal rhabdomyosarcoma at various sites and ovarian Sertoli-Leydig cell tumor. There have been occasional reported cases of ovarian germ cell tumors [mainly yolk sac tumor (YST)] harboring DICER1 PVs but, as far as we are aware, none of these has been proven to have a germline provenance. We report an unusual enteric variant of ovarian YST in a 28-yr-old woman associated with a germline PV c.901C>T (p.Gln301Ter) in exon 7 of DICER1, accompanied by a somatic (YST-only) hotspot mutation: c.5437G>A, p.E1813K. To our knowledge, this is the first report of an ovarian germ cell tumor associated with a germline DICER1 PV. We review other reported cases of ovarian germ cell tumor with DICER1 PVs and discuss the differential diagnosis of this unusual variant of YST which was originally diagnosed as a mucinous adenocarcinoma.

Uterine plexiform tumourlets: multifocal and solitary cases with subsets expressing melanocytic markers.

AIMS: Uterine plexiform tumourlets are traditionally regarded as microscopic epithelioid leiomyomas. They are typically solitary incidental findings, but may be multifocal (plexiform leiomyomatosis). We aim to report novel immunohistochemical and morphological findings, specifically the presence of spindled and epithelioid cell nodules, in these lesions. METHODS AND RESULTS: Three cases of plexiform leiomyomatosis and 16 solitary plexiform tumourlets were included. Two cases of plexiform leiomyomatosis and four solitary plexiform tumourlets demonstrated spindled and epithelioid cell nodules which, in one of the former cases, formed expansile masses up to 15 mm. The nodules demonstrated mild cytological atypia and occasional mitotic activity, and they were associated with a myxoid stroma and a lymphohistiocytic infiltrate which imparted a granulomatous appearance to the microscopic lesions. The plexiform tumourlets (solitary and multifocal) consistently expressed desmin, smooth muscle actin, ER and PR, and they commonly co-expressed melanocytic and perivascular epithelioid cell (PEC) markers HMB45, MiTF and cathepsin K. The spindled and epithelioid cell nodules were generally negative for myoid markers and hormone receptors, but expressed p16, cyclin D1 and TFE3. All lesions tested were negative for cytokeratin, S100, melanA, inhibin, EMA, ALK and BCOR; fluorescence in-situ hybridisation was negative for ALK, TFE3 and BCOR rearrangements in one of the larger spindled and epithelioid cell nodules. CONCLUSIONS: Plexiform tumourlets commonly co-express myoid and melanocytic markers and may represent part of the spectrum of gynaecological PEC-related lesions. Some cases are associated with spindled and epithelioid cell nodules that could potentially mimic other uterine myxoid neoplasms.

Loss of ARID1B and SMARCB1 expression are specific for the diagnosis of dedifferentiated/undifferentiated carcinoma in tumours of the upper gynaecological tract and cervix.

AIMS: Genomic inactivation of ARID1B in ARID1A-inactivated tumour and genomic inactivation of SMARCB1 represent two recurrent mechanisms, core SWItch/sucrose non-fermentable (SWI/SNF) complex inactivation, that are associated with de-differentiation in endometrial carcinoma. Approximately one-third of dedifferentiated/undifferentiated endometrial carcinomas (DDEC/UEC) show loss of ARID1B expression with a minor subset showing loss of SMARCB1 expression, but little is known regarding the specificity of ARID1B or SMARCB1 loss in gynaecological tract tumours in general. The aim of this study was to examine the frequency of ARID1B and SMARCB1 loss by immunohistochemistry in a series of gynaecological tract epithelial/mesenchymal neoplasms. METHODS AND RESULTS: We evaluated 1849 tumours that included 748 endometrial carcinomas, 101 uterine carcinosarcomas/adenosarcomas, 64 uterine sarcomas, 221 cervical carcinomas and 715 ovarian carcinomas/borderline tumours by tissue microarrays (TMA). We observed ARID1B loss in 35 of 86 (41%) and SMARCB1 loss in three of 86 (3%) DDEC/UEC, but not in any other uterine tumour types examined. ARID1B-deficient DDEC/UEC also showed concurrent loss of ARID1A expression. All SMARCB1-deficient tumours showed loss of MLH1 and PMS2, while 29 of 35 ARID1B-deficient tumours showed loss of MLH1 and PMS2 or loss of MSH6. All ovarian carcinomas/borderline tumours and cervical carcinomas showed intact expression of ARID1B and SMARCB1. CONCLUSION: Our findings indicate that the loss of expression of ARID1B or SMARCB1 by immunohistochemistry is highly specific for undifferentiated carcinoma among tumours of the upper gynaecological tract and cervix, and therefore can be used to identify these highly aggressive malignant tumours.

p53 immunohistochemical analysis of fusion-positive uterine sarcomas.

AIMS: Uterine sarcomas can be grouped into tumours with pathognomonic genetic fusions such as low-grade endometrial stromal sarcoma (LGESS), high-grade endometrial stromal sarcoma (HGESS), and inflammatory myofibroblastic tumour (IMT), and tumours lacking genetic fusions such as leiomyosarcoma (LMS) and undifferentiated uterine sarcoma (UUS). Members of the latter group frequently harbour TP53 mutations. The aim of this study was to evaluate TP53 mutations by the use of immunohistochemistry in fusion-positive uterine sarcomas. METHODS AND RESULTS: We performed p53 immunohistochemical staining on 124 uterine sarcomas harbouring genetic fusions and 38 fusion-negative LMSs and UUSs. These included 41 HGESSs with YWHAE, BCOR and BCORL1 fusions/rearrangements, 13 IMTs with ALK fusion, 12 sarcomas with NTRK1/3 fusion, three sarcomas with PDGFB fusion, and 55 LGESSs with JAZF1, SUZ12 and PHF1 fusions/rearrangements. All HGESSs, LGESSs, IMTs and sarcomas with PDGFB fusion showed wild-type p53 expression. Among NTRK1/3-positive sarcomas, a TPR-NTRK1-positive sarcoma with nuclear pleomorphism showed mutation-type p53 expression. The remaining 11 NTRK1/3-positive sarcomas showed wild-type p53 expression, except for the subclonal p53 mutation-type staining in a minor pleomorphic focus of an NTRK3-positive sarcoma. Twenty-one of 27 (78%) LMSs and six of nine (67%) UUSs showed mutation-type p53 expression. CONCLUSION: p53 immunohistochemistry may be considered in the initial work-up of a uterine sarcoma, as mutation-type staining would make a fusion-positive sarcoma very unlikely. Mutation-type p53 expression, however, can be seen in a small subset of NTRK1/3-positive sarcomas showing pleomorphic round/ovoid cell histology, which may represent a mechanism of progression in these tumours.

Atypical Microglandular Hyperplasia of Endocervix as the Presenting Feature of Plasminogen Deficiency.

A 30-yr-old patient with no significant past medical history presented with postcoital bleeding and was found to have fibrinous pseudomembranous lesions overlying and partly in continuity with the endocervical mucosa. Histologically, these were characterized by an atypical microglandular proliferation that was associated with extensive fibrinous exudate and a prominent neutrophil polymorph infiltrate. Ligneous stromal alteration was not identified but the changes prompted hematologic review which confirmed plasminogen deficiency. A subsequent endometrial biopsy also demonstrated degenerate glands within a fibrin-rich matrix. This is the third case demonstrating an association between atypical endocervical microglandular hyperplasia and plasminogen deficiency. The diagnosis should also be considered when biopsies demonstrate exuberant fibrin exudate even if ligneous disease is not present.

Stromal Endocrine Cell Micronests Associated With an Ovarian Mucinous Cystadenoma: Endocrine Cell Preservation (Pseudohyperplasia) Potentially Mimicking Stromal Sex Cord Proliferation or Tumor Microinvasion.

Endocrine cell micronests (ECMs) have been described only twice previously in the ovary, both in association with mucinous neoplasms exhibiting intraepithelial endocrine cell hyperplasia. We report a 31-yr-old patient with a mucinous cystadenoma in which ECMs were distributed in the stroma surrounding degenerate glandular elements. Immunohistochemistry demonstrated only sparse endocrine cells within the neoplastic glands. We postulate that the ECMs in this case reflected relative preservation of endocrine elements in the context of epithelial atrophy, a process more commonly encountered in gastrointestinal pathology. Ovarian ECMs should also be distinguished from stromal sex cord proliferations and tumor microinvasion.

The Value of DICER1 Mutation Analysis in "Subtle" Diagnostically Challenging Embryonal Rhabdomyosarcomas of the Uterine Cervix.

Embryonal rhabdomyosarcoma of the uterine cervix is a rare neoplasm which is almost invariably associated with pathogenic somatic or germline DICER1 mutations; patients with germline mutations have DICER1 syndrome. We report 2 subtle cervical embryonal rhabdomyosarcoma, one occurring in a 21-yr-old woman with a known history of DICER1 syndrome and the other in a 19-yr-old woman with no history of DICER1 syndrome or DICER1-associated neoplasms. Both neoplasms focally involved otherwise benign endocervical polyps and were characterized histologically by subtle areas of increased stromal cellularity, nuclear atypia and mitotic activity; there was focal nuclear staining of these areas with the skeletal muscle markers myogenin and myoD1. In both cases, demonstration of a somatic DICER1 RNase IIIb mutation in the tumor was instrumental in establishing the diagnosis. We believe these neoplasms represent the earliest discernible phase of cervical embryonal rhabdomyosarcoma. Pathologists should have a high index of suspicion when atypical stromal elements are present in endocervical polyps and immunohistochemistry together with DICER1 sequencing will assist in diagnosis.

Lynch syndrome associated endometrial carcinomas in Western Australia: an analysis of universal screening by mismatch repair protein immunohistochemistry.

BACKGROUND: In 2016 universal screening with mismatch repair protein immunohistochemistry in all newly diagnosed endometrial carcinomas was introduced in Western Australia. OBJECTIVE: To compare the prevalence of Lynch syndrome associated endometrial carcinomas between 2016 and 2019 with a historical control (2015). Additionally, to compare the number of cases appropriately referred for genetic assessment. METHODS: A cross-sectional study of cases presented at the Western Australia gynecologic oncology tumor board was carried out. The primary outcome was the prevalence of Lynch syndrome associated endometrial carcinomas. A secondary outcome was the number of cases appropriately referred for genetic assessment. The following variables were extracted: date of birth; age at diagnosis; vital status; tumor mismatch repair protein expression status (retained or lost) and if lost, the specific mismatch repair protein deficiency; patients who were referred to a genetic clinic; and family history, if recorded. Data were collected from the clinical databases of the Familial Cancer Program at Genetic Services of Western Australia and WOMEN Center, to determine whether patients were appropriately referred for genetic evaluation and to ascertain the results of genetic testing. RESULTS: Between 2016 and 2019, there were 1040 new endometrial carcinomas. Tumors of 883 (85%) patients underwent mismatch repair protein immunohistochemistry compared with 117 of 199 patients (59%) in 2015 (χ2 73.14, p<0.001). Of 883 tumors tested, 242 (27%) showed loss of mismatch repair protein expression. In 2015, 30 (26%) tumors of 117 tested showed loss of mismatch repair protein expression. During the 4 years of universal screening, 13 (1.5%) of 883 patients screened were diagnosed with Lynch syndrome compared with 2 (1.7%) of 117 in 2015 (Fisher's exact test 0.04, p=0.69). In 2015, 11 (37%) of 30 patients with loss of mismatch repair protein expression were not referred for genetic assessment compared with 36 (17%) of 209 patients in the universal screening group (χ2 6.28, p=0.02). No cases of Lynch syndrome were diagnosed in patients aged over 70 years. CONCLUSIONS: Universal immunohistochemical screening did not increase the proportion of Lynch syndrome associated endometrial carcinomas identified, although the study was underpowered to detect small differences. There was an improvement in appropriate referrals for genetic assessment.

SWI/SNF-deficient malignancies of the female genital tract.

Mutations and other molecular events involving subunits of the SWI/SNF chromatin remodelling complex are common in a wide variety of malignancies, including those arising at various sites in the female genital tract. Endometrioid and clear cell carcinomas in the uterine corpus and ovary not uncommonly contain mutations in ARID1A and these also occur in other endometriosis-associated ovarian neoplasms such as seromucinous tumours. In these organs, mutations in SMARCA4, SMARCB1, ARID1A and ARID1B (with subsequent loss of corresponding protein expression as a reliable surrogate) are relatively common in undifferentiated carcinomas, including the undifferentiated component of dedifferentiated carcinoma. SMARCA4 mutations are extremely common (almost ubiquitous) in small cell carcinoma of the ovary of hypercalcaemic type (SCCOHT), occurring in about 98% of these neoplasms, often in association with epigenetic SMARCA2 loss. SMARCB1-deficient vulval neoplasms include epithelioid sarcoma and myoepithelial carcinoma, as well as related malignancies which defy easy classification. Recently the spectrum of SWI/SNF deficient female genital malignancies has been expanded to include SMARCA4-deficient undifferentiated uterine sarcoma and mural nodules of anaplastic carcinoma in ovarian mucinous neoplasms.

Significantly greater prevalence of DICER1 alterations in uterine embryonal rhabdomyosarcoma compared to adenosarcoma.

Embryonal rhabdomyosarcomas (ERMS) account for 2-3% of cancers in pediatric and adolescent populations. They are rarer in adults. We and others have reported that ERMS arising in the uterine cervix may harbor mutations in the gene encoding the microRNA biogenesis enzyme, DICER1, but a large series of cases has not been published. In the uterus, distinguishing ERMS from adenosarcoma can be very challenging, even for expert pathologists, and DICER1 alterations have been identified in a variable subset of uterine adenosarcomas. We hypothesized that DICER1 genetic testing may be useful in distinguishing between ERMS and adenosarcoma. We conducted a central pathology review-based study of 64 tumors initially thought to be uterine ERMS or adenosarcoma; 19 neoplasms had a consensus diagnosis of ERMS, 27 of adenosarcoma and for 18, no consensus diagnosis was reached. The median age at diagnosis was 30 years (range 2.5-69) for ERMS, 57.5 years (range 27-82) for adenosarcoma, and 65.5 years (range 32-86) for no consensus cases. In our series, the DICER1 mutation prevalence differed between the three groups: DICER1 alterations were present in 18/19 (95%) ERMS, 7/27 (26%) adenosarcomas (p < 0.001), and 4/18 (22%) no consensus cases. A germline alteration was present in 6/12 ERMS patients tested versus 0/6 adenosarcoma patients. Thus, although DICER1 mutations are near ubiquitous in uterine ERMS and are significantly less common in uterine adenosarcoma, DICER1 testing is only of value in distinguishing between the two neoplasms when a DICER1 mutation is absent, as this is helpful in excluding ERMS. On review of the clinical and radiological features of the single DICER1 wild-type cervical ERMS, this was thought most likely to be of vaginal origin. Given the significant prevalence of DICER1 germline pathogenic variants in uterine ERMS, all patients with this diagnosis should be referred to a genetics service.

High-grade transformation of low-grade endometrial stromal sarcomas lacking YWHAE and BCOR genetic abnormalities.

High-grade histologic transformation of low-grade endometrial stromal sarcoma (LGESS) is rare. Here, we describe the clinicopathologic features and gene fusion status of 12 cases (11 primary uterine corpus and 1 primary vaginal), 11 diagnosed prospectively from 2016, and 1 retrospectively collected. Targeted RNA sequencing and/or fluorescence in situ hybridization was employed in all cases. High-grade transformation was seen at the time of initial diagnosis in eight patients and at the time of recurrence in four patients, 4-11 years after initial diagnosis of LGESS. High-grade morphology consisted of generally uniform population of round to epithelioid cells with enlarged nuclei one to two times larger than a lymphocyte, visible nucleoli, and increased mitotic index (range, 6-30; median, 16 per 10 high-power fields); there was often an associated sclerotic and/or myxoid stroma. Estrogen receptor, progesterone receptor, and CD10 expression was absent or significantly decreased (compared with the low-grade component) in the high-grade foci of five tumors. One tumor demonstrated positive (diffuse and strong) cyclin D1 and BCOR staining. p53 staining was wild type in both components of all eight tumors tested. JAZF1-SUZ12 (n = 6), JAZF1-PHF1 (n = 3), EPC1-PHF1, (n = 1), or BRD8-PHF1 (n = 1) fusions were detected in 11 tumors; no fusions were found in one by targeted RNA sequencing. Patients presented with FIGO stages I (n = 4), II (n = 4), III (n = 1), and IV disease (n = 2). Median overall survival calculated from the time of histologic transformation was 22 months (range, 8 months to 8 years) with five patients who died of disease 8-18 months after transformation. High-grade transformation may occur in LGESS with JAZF1 and PHF1 rearrangements at the time of or years after initial diagnosis. Such high-grade transformation is characterized by nuclear enlargement, prominent nucleoli, and increased mitotic index compared with typical LGESS. Histologic high-grade transformation may herald aggressive behavior.

Endometrial intravascular thrombi are typically associated with shedding but may be the sentinel feature of an underlying thrombotic disorder.

AIMS: Following the identification of endometrial intravascular thrombi (IVT) as the presenting feature in a patient with antiphospholipid syndrome, additional biopsy specimens were reviewed to determine the frequency and histological associations of IVT in the endometrium. METHODS AND RESULTS: Eighty-five additional biopsies were reviewed including 44 consecutive cases demonstrating shedding changes (both menstrual and non-cyclical), 30 cases without shedding (normal and non-cyclical), and 11 cases in which unusually prominent IVT had been recorded upon initial histological assessment. In the shedding group, IVT were significantly more common in biopsies showing disordered proliferative endometrium (DPE, 4/7 cases) than normal menstrual appearances (4/22 cases), and organising vascular changes were seen only in the former. IVT in DPE cases were also commonly multifocal and sometimes involved abnormal ectatic vessels. None of the 30 non-shedding cases demonstrated IVT. Eight of the 11 biopsies with prominent IVT demonstrated DPE and shedding but three cases demonstrated otherwise normal cyclical appearances. CONCLUSIONS: IVT may be seen occasionally in normal menstrual endometrium but are more characteristic of DPE, and organising vascular changes are suggestive of abnormal haemostasis. An underlying thrombotic disorder may be considered when endometrial IVT occur in the absence of shedding changes.

Novel POLE pathogenic germline variant in a family with multiple primary tumors results in distinct mutational signatures.

We describe a family in which four siblings exhibited multiple or classic colonic polyposis with or without colorectal carcinoma (CRC). One female developed three primary tumors, including CRC and carcinomas of the ovary and breast. Whole-exome sequencing of germline DNA from affected and unaffected individuals revealed a novel missense mutation in the exonuclease domain of POLE (c.833C>A; p.Thr278Lys) associated with a highly penetrant, autosomal-dominant inheritance pattern. Functional studies in yeast and demonstration of a high mutational burden in the available tumors confirmed the pathogenicity of the novel variant. Prominent POLE-deficient somatic mutational signatures were seen in the CRCs, but in contrast, a mutational signature typical of concomitant tumoral loss of POLE and mismatch-repair function (POLE-exo* /MSI) was noted in the breast cancer. The breast cancer also showed distinctive pathological characteristics that reflect the presence of both the germline POLE variant and the secondary somatic MMR alterations.

Pathological chemotherapy response score is prognostic in tubo-ovarian high-grade serous carcinoma: A systematic review and meta-analysis of individual patient data.

OBJECTIVE: There is a need to develop and validate biomarkers for treatment response and survival in tubo-ovarian high-grade serous carcinoma (HGSC). The chemotherapy response score (CRS) stratifies patients into complete/near-complete (CRS3), partial (CRS2), and no/minimal (CRS1) response after neoadjuvant chemotherapy (NACT). Our aim was to review current evidence to determine whether the CRS is prognostic in women with tubo-ovarian HGSC treated with NACT. METHODS: We established an international collaboration to conduct a systematic review and meta-analysis, pooling individual patient data from 16 sites in 11 countries. Patients had stage IIIC/IV HGSC, 3-4 NACT cycles and >6-months follow-up. Random effects models were used to derive combined odds ratios in the pooled population to investigate associations between CRS and progression free and overall survival (PFS and OS). RESULTS: 877 patients were included from published and unpublished studies. Median PFS and OS were 15 months (IQR 5-65) and 28 months (IQR 7-92) respectively. CRS3 was seen in 249 patients (28%). The pooled hazard ratios (HR) for PFS and OS for CRS3 versus CRS1/CRS2 were 0·55 (95% CI, 0·45-0·66; P < 0·001) and 0·65 (95% CI 0·50-0·85, P = 0·002) respectively; no heterogeneity was identified (PFS: Q = 6·42, P = 0·698, I2 = 0·0%; OS: Q = 6·89, P = 0·648, I2 = 0·0%). CRS was significantly associated with PFS and OS in multivariate models adjusting for age and stage. Of 306 patients with known germline BRCA1/2 status, those with BRCA1/2 mutations (n = 80) were more likely to achieve CRS3 (P = 0·027). CONCLUSIONS: CRS3 was significantly associated with improved PFS and OS compared to CRS1/2. This validation of CRS in a real-world setting demonstrates it to be a robust and reproducible biomarker with potential to be incorporated into therapeutic decision-making and clinical trial design.