Frequent loss of claudin-4 expression in dedifferentiated and undifferentiated endometrial carcinomas

Claudins in Cancer: A Current and Future Therapeutic Target

Claudins are a family of 27 proteins that have an important role in the formation of tight junctions. They also have an important function in ion exchange, cell mobility, and the epithelial-to-mesenchymal transition, the latter being very important in cancer invasion and metastasis. Therapeutic targeting of claudins has been investigated to improve cancer outcomes. Recent evidence shows improved outcomes when combining monoclonal antibodies against claudin 18.2 with chemotherapy for patients with gastroesophageal junction cancer. Currently, chimeric antigen receptor T-cells targeting claudin 18 are under investigation. In this review, we will discuss the major functions of claudins, their distribution in the normal as well as cancerous tissues, and their effect in cancer metastasis, with a special focus on the therapeutic targeting of claudins to improve cancer outcomes.

Uncommon and Difficult High-Grade Endometrial Carcinomas

This article presents features of uncommon high-grade endometrial carcinomas that often pose a significant diagnostic challenge. An update on undifferentiated and dedifferentiated endometrial carcinoma is first provided, followed by discussions on more recently defined entities such as mesonephric-like carcinoma of the endometrium and gastric-type endometrial carcinomas. Finally, endometrial carcinoma with germ cell or trophoblastic-like components is discussed.

ZEB1 expression is frequently detected in undifferentiated and dedifferentiated carcinomas, but is not specific among endometrial carcinomas

AIMS

The pathological diagnosis of undifferentiated and dedifferentiated endometrial carcinomas (UC/DCs) is prognostically important. However, undifferentiated components may be confused with other subtypes, particularly grade 3 endometrioid carcinomas (G3ECs). ZEB1 has recently been identified as a promising marker because it is frequently expressed in the undifferentiated components of UC/DCs, but not in other carcinomas. Therefore, we herein evaluated the diagnostic utility of ZEB1 with an emphasis on distinguishing between UC/DCs and G3ECs using an expanded cohort of endometrial carcinomas and carcinosarcomas.

METHODS AND RESULTS

Immunostaining for ZEB1 was performed on whole-tissue sections of 19 UC/DCs, 194 non-UC/DC endometrial carcinomas, and 29 carcinosarcomas. Staining was defined as negative (<5%), focal (5-50%), and diffuse expression (>50%). ZEB1 was expressed in 84% of the undifferentiated components of UC/DCs (diffuse in 14, focal in two). Focal expression was observed in eight non-UC/DC endometrial carcinomas and diffuse expression in seven, with the latter comprising G3ECs (4/76), serous carcinoma (1/37), clear cell carcinoma (1/21), and neuroendocrine carcinoma (1/3). Epithelial differentiation was morphologically and immunohistochemically less evident in G3ECs and neuroendocrine carcinoma with diffuse ZEB1 expression. All carcinosarcomas showed diffuse ZEB1 expression in their sarcomatous components.

CONCLUSION

Immunostaining for ZEB1 was sufficiently sensitive to detect undifferentiated components. Diffuse ZEB1 expression showed high specificity for distinguishing between undifferentiated components and G3ECs; however, ZEB1 expression was not entirely specific to UC/DCs. The integration of ZEB1 into the diagnosis of UC/DCs requires careful examinations to exclude other tumours, such as less differentiated G3ECs, neuroendocrine carcinomas, and carcinosarcomas.

The value of SOX2 in the differential diagnosis of SMARCA4 (BRG1)-deficient uterine neoplasms

SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4/BRG1) deficient undifferentiated uterine sarcoma (SDUS) is a recently described uterine sarcoma. It is characterized by predominantly rhabdoid or large epithelioid cells with abundant cytoplasm and varying components of small and spindle cells, resembling the "large cell variant" of small cell carcinoma of ovary, hypercalcemic type (SCCOHT). In addition, SMARCA4 inactivating mutations have been described as the driver mutations in SDUS. However, undifferentiated (UDEC) and dedifferentiated endometrial carcinomas (DDEC) may show some clinical and morphological overlaps with SDUS, and about 20% reported UDEC/DDEC cases also have loss expression of SMARCA4. SDUS is a very aggressive disease and universally lethal in all reported cases. Differentiating SDUS from UDEC/DDEC is relevant for the prognosis, pathogenesis and possible targeted therapies for the disease. In this study, we compared the clinical, morphological, immunohistochemical and molecular characteristics of 10 tumors including 2 SDUS, 2 SCCOHT, 1 uterine carcinoma with neuroendocrine differentiation (UDEC?) and 5 UDEC/DDEC. All 5 UDEC/DDEC cases showed strong and diffuse nuclear positivity for SOX2, while all SCCOHT and SDUS cases were completely negative. We concluded that SOX2 could be a useful marker for the differential diagnosis between SDUS and UDEC/DDEC.

The Roles of Tricellular Tight Junction Protein Angulin-1/Lipolysis-Stimulated Lipoprotein Receptor (LSR) in Endometriosis and Endometrioid-Endometrial Carcinoma

Tight junction proteins play roles beyond permeability barriers functions and control cell proliferation and differentiation. The relation between tight junctions and the signal transduction pathways affects cell growth, invasion and migration. Abnormality of tight junction proteins closely contributes to epithelial mesenchymal transition (EMT) and malignancy of various cancers. Angulin-1/lipolysis-stimulated lipoprotein receptor (LSR) forms tricellular contacts that has a barrier function. Downregulation of angulin-1/LSR correlates with the malignancy in various cancers, including endometrioid-endometrial carcinoma (EEC). These alterations have been shown to link to not only multiple signaling pathways such as Hippo/YAP, HDAC, AMPK, but also cell metabolism in ECC cell line Sawano. Moreover, loss of angulin-1/LSR upregulates claudin-1, and loss of apoptosis stimulating p53 protein 2 (ASPP2) downregulates angulin-1/LSR. Angulin-1/LSR and ASPP2 concentrate at both midbody and centrosome in cytokinesis. In EEC tissues, angulin-1/LSR and ASPP2 are reduced and claudin-2 is overexpressed during malignancy, while in the tissues of endometriosis changes in localization of angulin-1/LSR and claudin-2 are seen. This review highlights how downregulation of angulin-1/LSR promotes development of endometriosis and EEC and discusses about the roles of angulin-1/LSR and its related proteins, including claudins and ASPP2.

Re-expression of SMARCA4/BRG1 in small cell carcinoma of ovary, hypercalcemic type (SCCOHT) promotes an epithelial-like gene signature through an AP-1-dependent mechanism

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare and aggressive form of ovarian cancer. SCCOHT tumors have inactivating mutations in SMARCA4 (BRG1), one of the two mutually exclusive ATPases of the SWI/SNF chromatin remodeling complex. To address the role that BRG1 loss plays in SCCOHT tumorigenesis, we performed integrative multi-omic analyses in SCCOHT cell lines +/- BRG1 reexpression. BRG1 reexpression induced a gene and protein signature similar to an epithelial cell and gained chromatin accessibility sites correlated with other epithelial originating TCGA tumors. Gained chromatin accessibility and BRG1 recruited sites were strongly enriched for transcription-factor-binding motifs of AP-1 family members. Furthermore, AP-1 motifs were enriched at the promoters of highly upregulated epithelial genes. Using a dominant-negative AP-1 cell line, we found that both AP-1 DNA-binding activity and BRG1 reexpression are necessary for the gene and protein expression of epithelial genes. Our study demonstrates that BRG1 reexpression drives an epithelial-like gene and protein signature in SCCOHT cells that depends upon by AP-1 activity.

Clinico-pathological features associated with mismatch repair deficiency in endometrial undifferentiated/dedifferentiated carcinoma: A systematic review and meta-analysis

BACKGROUND

Endometrial undifferentiated/dedifferentiated carcinoma (UDC/DDC) is a recently described aggressive variant of endometrial carcinoma, which shows mismatch repair (MMR) deficiency in about half of cases.

AIM

To assess whether MMR-deficient UDC/DDC have distinct clinico-pathological features.

MATERIALS AND METHODS

A systematic review and meta-analysis was performed by searching 4 electronic databases from their inception to October 2020 for all studies reporting clinicopathological characteristics of UDC/DDC series. Student t-test (for continuous variables), Cox regression analysis (for overall survival) and odds ratio (OR, for dichotomous variables) were used with a significant p-value < 0.05; data were pooled by using a random effect model.

RESULTS

Twelve studies were included. MMR-deficiency was significantly associated with older age (p = 0.024), p53-wild-type (p = 0.005), ARID1A loss (p = 0.001) and PD-L1 expression (p = 0.019), but not with overall survival (p = 0.307), extension beyond corpus (p = 0.787) or beyond uterus (p = 0.403), presence of a differentiated component (p = 0.461), loss of expression of cytokeratins (p = 0.698), EMA (p = 0.309), estrogen receptor (p = 0.605), PAX8 (p = 0.959), SMARCA4/BRG1 (p = 0.321), SMARCB1/INI1 (p = 0.225) or claudin-4 (p = 0.094), or POLE exonuclease domain mutation p = (0.773).

CONCLUSIONS

In UDC/DDC, MMR-deficiency appears associated with older age, p53-wild type and ARID1A loss, suggesting the possibility of a distinct pathway underlying dedifferentiation; the association with PD-L1 expression is attributable to the high mutational load and may have therapeutic implications. On the other hand, MMR-deficiency appears not to be associated with prognosis, stage, loss of differentiation markers or POLE mutation.

A report of two cases of dedifferentiated endometrioid carcinoma: A newly described underrecognized tumor of poor prognosis

Dedifferentiated endometrioid carcinoma or dedifferentiated endometrioid adenocarcinoma (DEAC) is defined by the presence of undifferentiated carcinoma with endometrioid carcinoma. Undifferentiated component can be misinterpreted as solid component of high-grade endometrioid carcinoma or sarcomatous component of malignant mixed mullerian tumor. We present two cases of DEAC. Two postmenopausal women underwent hysterectomy for vaginal bleeding. Microscopically, sections from the endometrial tumors showed a biphasic growth consisting of an undifferentiated component and a glandular component with sharp transition between the two components. The undifferentiated component showed focal positivity for cytokeratin and vimentin, while glandular component was diffusely positive for cytokeratin and negative for vimentin expression.

Undifferentiated and dedifferentiated neoplasms of the female genital tract

Undifferentiated neoplasms in the female gynecologic tract comprise two main groups-undifferentiated carcinoma, most common in the endometrium and ovary, and undifferentiated uterine sarcoma, although tumors with an undifferentiated appearance may occur in all gynecologic organs. Their differential diagnosis is broad and generous sampling, careful morphological evaluation, judicious use of immunohistochemistry, and in many cases, molecular testing is often essential in the diagnostic work-up. As some of these neoplasms fail to respond to conventional chemotherapy regimens and/or radiation therapy, targeted therapy may be valuable in treating these highly aggressive tumors, thus the importance of precise diagnosis. In this review we discuss the clinicopathological features of undifferentiated carcinoma, dedifferentiated carcinoma, and undifferentiated uterine sarcoma, followed by a comprehensive analysis of morphological mimickers. Finally, we briefly review ovarian and lower genital tract tumors with an undifferentiated histological appearance.

Undifferentiated endometrial carcinoma arising in the background of high-grade endometrial carcinoma - Expanding the definition of dedifferentiated endometrial carcinoma

Dedifferentiated endometrial adenocarcinoma (DEC) is defined by the coexistence of undifferentiated carcinoma with low-grade (FIGO grade 1 or 2) endometrioid carcinoma. Few cases of DEC arising in the background of high-grade carcinoma (DEC-HG) have been reported, however, this phenomenon is poorly characterized. In this study we describe the morphologic, immunohistochemical and clinico-pathologic characteristics of DEC-HG. 18 DECs were diagnosed at our institution between 2008-2019, and in 11 (61%), the undifferentiated component was associated with high-grade carcinoma (8 endometrioid FIGO grade 3, 2 with ambiguous features, 1 serous). The remaining 7 (39%) represented DEC-LG (3 FIGO grade 1 and 4 FIGO grade 2). 7/11 (64%) patients with DEC-HG presented with advanced stage (FIGO stage III/IV), whereas most with DEC-LG (6/7, 86%) were stage I. On follow up, 2 patients in the DEC-HG group died of disease and 2 had progressive disease within 2 months of surgery. There was only one recurrence in the DEC-LG, 6 months post-surgery. The DEC component in both groups showed similar morphology and immunophenotype, with predominantly focal or complete loss of expression of pan-keratin, EMA, E-cadherin, CK8/18, PAX8 and ER. The DEC component in the DEC-HG group had wild-type p53 expression in 8/11 (73%) cases, loss of MLH1 and PMS2 in 6/11 (55%) and loss of SMARCA4 in 3/9 (33%). Although numbers are small, we show that DEC-HG is a previously under-recognized phenomenon, with morphologic and immunophenotypic similarities to DEC-LG, which supports expanding the definition of DEC to include DEC-HG. DEC-HG may be more aggressive than DEC-LG.

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.

Review of SMARCA4 (BRG1)-deficient carcinomas following a malignant pleural effusion specimen confounded by reduced claudin-4 expression

SMARCA4-deficient neoplasms are recently characterized high-grade malignancies associated with a poor prognosis. The SMARCA4 gene encodes BRG1, which is part of the SWI/SNF complex. SMARCA4-deficient neoplasms have an undifferentiated, often rhabdoid morphology, and demonstrate loss of BRG1 nuclear expression on immunohistochemistry. These neoplasms have become increasingly recognized and diagnosed in tissue specimens, but their features in cytologic specimens are poorly defined in the literature. The review is introduced by a diagnostically challenging case of a SMARCA4-deficient carcinoma involving a pleural fluid specimen in which the carcinoma cells demonstrated greatly reduced claudin-4 expression in the setting of strong, diffuse BerEP4 expression. Most of the malignant cells also demonstrated positive cytoplasmic staining for PAS and all were PAS-diastase negative, suggesting that the cytoplasm contained glycogen granules.

SWI/SNF protein and claudin-4 expression in anaplastic carcinomas arising in mucinous tumours of the ovary and retroperitoneum

AIMS

Anaplastic carcinoma arising in a mucinous tumour of the ovary and rarely in the retroperitoneum is an uncommon neoplasm with three morphological patterns; rhabdoid, sarcomatoid and pleomorphic. We investigated expression of switch/sucrose non-fermentable (SWI/SNF) chromatin remodelling complex components and claudin-4 expression.

METHODS AND RESULTS

Twenty-two ovarian and three retroperitoneal mucinous tumours were investigated using antibodies against SMARCB1, SMARCA4, SMARCA2, ARID1A and claudin-4. Loss of nuclear staining for any SWI/SNF protein was observed in the anaplastic component of nine of 25 (36%), with retained expression within the mucinous component of all tumours. Five (56%) showed loss of more than one protein, with dual loss of SMARCA4 and SMARCA2 in two, loss of SMARCA2 and ARID1A in two and loss of SMARCB1 and SMARCA2 in one. Retained expression of claudin-4 was seen in 39% of the anaplastic carcinomas and within the mucinous component of all tumours. Rhabdoid morphology was associated with poor prognosis [stages III or IV disease (six of six, 100% versus four of 14, 29%; P = 0.0108] and death from disease (three of four, 75% versus one of 13, 8%; P = 0.0223). Although loss of a SWI/SNF protein was not significantly associated with death from disease (three of five, 60% versus one of 12, 8%; P = 0.0525), it showed a trend in correlation with poor prognosis and was often noted in tumours with rhabdoid morphology within this small cohort.

CONCLUSIONS

Our report adds to the growing list of female genital tract malignancies with loss of SWI/SNF proteins, underlining their broad differential diagnosis and the importance of careful, context-dependent interpretation of SWI/SNF protein loss.

SWI/SNF Complex Mutations in Gynecologic Cancers: Molecular Mechanisms and Models

The SWI/SNF (mating type SWItch/Sucrose NonFermentable) chromatin remodeling complexes interact with histones and transcription factors to modulate chromatin structure and control gene expression. These evolutionarily conserved multisubunit protein complexes are involved in regulating many biological functions, such as differentiation and cell proliferation. Genomic studies have revealed frequent mutations of genes encoding multiple subunits of the SWI/SNF complexes in a wide spectrum of cancer types, including gynecologic cancers. These SWI/SNF mutations occur at different stages of tumor development and are restricted to unique histologic types of gynecologic cancers. Thus, SWI/SNF mutations have to function in the appropriate tissue and cell context to promote gynecologic cancer initiation and progression. In this review, we summarize the current knowledge of SWI/SNF mutations in the development of gynecologic cancers to provide insights into both molecular pathogenesis and possible treatment implications for these diseases.

A Comprehensive Review of Biomarker Use in the Gynecologic Tract Including Differential Diagnoses and Diagnostic Pitfalls

Morphologic (ie, hematoxylin and eosin) evaluation of the Mullerian tract remains the gold standard for diagnostic evaluation; nevertheless, ancillary/biomarker studies are increasingly utilized in daily practice to assist in the subclassification of gynecologic lesions and tumors. The most frequently utilized "biomarker" technique is immunohistochemistry; however, in situ hybridization (chromogenic and fluorescence), chromosomal evaluation, and molecular analysis can also be utilized to aid in diagnosis. This review focuses on the use of immunohistochemistry in the Mullerian tract, and discusses common antibody panels, sensitivity and specificity of specific antibodies, and points out potential diagnostic pitfalls when using such antibodies.

Claudins: New Players in Human Fertility and Reproductive System Cancers

Claudins are major integral proteins of tight junctions (TJs), the apical cell-cell adhesions that enable maintaining polarity of epithelial cells, their differentiation, and cell signaling. A number of studies have indicated that claudins might play a crucial role in both physiology and pathogenesis. Their tissue-specific expression was originally linked to the development of different types of cancer and triggered a hope to use them as diagnostic or prognostic markers. However, it seems that their expression is more complex than that, and undoubtedly, claudins participate in one of the most important molecular events in cells. This review summarizes the recent research evaluating the role of claudins in fertility and the most common endocrine-dependent cancers in the reproductive system and highlights the crucial role of claudins both in human fertility and the most common cancers.

SMARCA4-deficient Thoracic Sarcomas: Clinicopathologic Study of 30 Cases With an Emphasis on Their Nosology and Differential Diagnoses

SMARCA4-deficient thoracic sarcoma (SMARCA4-DTS) is a recently described entity with an aggressive clinical course and specific genetic alterations of the BAF chromatin remodeling complex. In the present study, we reviewed the clinical and pathologic features of 30 cases of SMARCA4-DTS, discussed its main differential diagnoses and the challenging diagnostic scenarios that the average pathologist may face. In addition, we tested the specificity of the "SMARCA4-DTS immunohistochemical signature" (co-loss of SMARCA4 and SMARCA2 with overexpression of SOX2) in a large cohort of intrathoracic malignancies. Patients ranged from 28 to 90 years of age (median: 48 y), with a marked male predominance (male:female=9:1) and they were usually smokers. Tumors were generally large compressive masses located in the mediastinum (n=13), pleura (n=5), lung (n=2) or in 2 or more of these topographies (n=10). Treatment strategies were varied, including 1 case treated with EZH2 inhibitors. Median overall survival was 6 months. Histologically, tumors were poorly differentiated frequently showing rhabdoid features. A subset of cases showed a focal myxoid stroma (7%, n=2/30) and rare cases displayed a previously unreported pattern simulating desmoplastic small round cell tumors (7%, n=2/30). Making a diagnosis was challenging when dealing with biopsy material from massively necrotic tumors and in this setting the expression of SOX2, CD34, and SALL4 proved useful. All tested cases displayed concomitant loss of SMARCA4 and SMARCA2 and most tumors expressed epithelial markers (Pan-keratin or EMA) (n=29/30), SOX2 (n=26/27), and CD34 (n=17/27). SMARCB1 expression was retained in all cases (23/23). SALL4 and Claudin-4 were expressed in a subset of cases (n=7/21 and 2/19, respectively). TTF-1 and P63 were focally expressed in 1 case each. P40 and NUT were not expressed (0/23 and 0/20, respectively) The SMARCA4-DTS immunohistochemical signature was both sensitive and specific, with only a subset of small cell carcinoma of the ovary hypercalcemic type showing overlapping phenotypes. Our study confirms and expands the specific features of SMARCA4-DTS, emphasizing the fact that they can be straightforwardly identified by pathologists.

SMARCA4-Deficient Thoracic Sarcomatoid Tumors Represent Primarily Smoking-Related Undifferentiated Carcinomas Rather Than Primary Thoracic Sarcomas

Introduction:

Highly aggressive thoracic neoplasms characterized by SMARCA4 (BRG1) deficiency and undifferentiated round cell or rhabdoid morphology have been recently described and proposed to represent thoracic sarcomas. However, it remains unclear whether such tumors may instead represent sarcomatoid carcinomas, and how their clinicopathologic characteristics compare with those of nonsarcomatoid SMARCA4-deficient non–small cell lung carcinomas (SD-NSCC).

Methods:

We identified 22 SMARCA4-deficient thoracic sarcomatoid tumors (SD-TSTs) with round cell and/or rhabdoid morphology and 45 SD-NSCCs, and comprehensively analyzed their clinicopathologic, immunohistochemical, and genomic characteristics using 341–468 gene next-generation sequencing and other molecular platforms.

Results:

The relationship of SD-TSTs with NSCC was supported by (1) the presence of NSCC components juxtaposed with sarcomatoid areas in five cases, (2) focal expression of NSCC lineage markers TTF1 or p40 in four additional cases, (3) smoking history in all except one patient (mean = 51 pack-years), accompanied by genomic smoking signature, and (4) high tumor mutation burden (mean = 14.2 mutations per megabase) and mutations characteristic of NSCC in a subset. Compared with SD-NSCCs, SD-TSTs exhibited considerably larger primary tumor size (p < 0.0001), worse survival (p = 0.004), and more frequent presentation at younger age (30–50 years) despite heavier smoking history. Distinctive pathologic features of SD-TSTs included consistent lack of adhesion molecule claudin-4, SMARCA2 (BRM) codeficiency, and frequent expression of stem cell markers.

Conclusions:

SD-TSTs represent primarily smoking-associated undifferentiated/de-differentiated carcinomas rather than primary thoracic sarcomas. Despite their histogenetic relationship with NSCC, these tumors have unique clinicopathologic characteristics, supporting their recognition as a distinct entity. Further studies are warranted to determine therapeutic approaches to this novel class of exceptionally aggressive thoracic tumors.

SMARCA4 inactivation defines a subset of undifferentiated uterine sarcomas with rhabdoid and small cell features and germline mutation association

A rare subset of aggressive SMARCA4-deficient uterine sarcomas has been recently proposed, with only a limited number of cases having been previously described. Here, we identify 16 additional cases of SMARCA4-deficient uterine sarcoma from the database of a large, CLIA-certified and CAP-accredited, reference molecular laboratory, and we expand on their clinicopathological and genomic features. Median patient's age was 49 years (range 32-70). Most tumors were aggressive with distant metastasis. SMARCA4-deficient uterine sarcoma demonstrated predominantly rhabdoid or large epithelioid cells with abundant cytoplasm, but also had varying degrees of small cell and spindle cell morphology. Tumors were microsatellite stable and exhibited no other or only few co-occurring genomic alterations by comprehensive genomic profiling. We discovered one patient, who developed SMARCA4-deficient uterine sarcoma at the age of 55, had a germline SMARCA4 mutation, whose daughter had previously died of small cell carcinoma of the ovary, hypercalcemic type, at the age of 32. Our data support the notion that SMARCA4 inactivation is the driver oncogenic event of a morphologically and molecularly distinct form of uterine sarcoma. Identification of SMARCA4-deficient uterine sarcomas may be clinically important due to their aggressive behavior, germline association, and emerging targeted therapies.

[Un- and dedifferentiated endometrial carcinoma : A rare entity with a wide range of differential diagnosis]

Dedifferentiated endometrial carcinomas (ECs) are composed of undifferentiated EC and a FIGO grade 1 or 2 endometrioid carcinoma. The undifferentiated component represents a malignant epithelial neoplasm with no obvious differentiation and immunohistochemical loss of PAX8, E‑cadherin and focal expression of EMA and/or CK18 and the predominant presence of nuclear staining for INI1 (SMARCB1) and BRG1 (SMARCA4). The main differential diagnoses include poorly differentiated endometrioid EC, neuroendocrine carcinoma, lymphoma, plasmocytoma, high-grade endometrial stromal sarcomas, undifferentiated uterine sarcomas (UUS), carcinosarcomas, and metastases to the endometrium. The histogenesis is not yet fully understood and molecular data are still limited. Some tumors represent a loss of MHL1 and PMS2 staining due to MLH1-promotor methylation. Rare cases are associated with Lynch syndrome or POLE mutation. The un- or dedifferentiated EC represents a high-grade endometrial carcinoma that requires extended surgery and indicates a poor prognosis. In cases with mismatch repair protein deficiency or POLE mutation, immuno-oncological treatment with checkpoint inhibitors are a therapeutic option.

Rapid progression of disease in two cases of undifferentiated endometrial carcinoma

Undifferentiated endometrial carcinoma, a rare histopathologic diagnosis, has a poor prognosis with high risk of progression during or shortly after completion of adjuvant treatment. We present two cases of undifferentiated endometrial carcinoma: one in a postmenopausal female who experienced recurrent disease immediately after completion of adjuvant treatment and one in a premenopausal female who experienced disease progression while receiving adjuvant treatment. These cases exemplify the aggressive behavior of undifferentiated endometrial carcinoma and suggest the need for a more effective treatment in the upfront setting than the current standard of care for endometrioid endometrial adenocarcinoma.