BCOR is a robust diagnostic immunohistochemical marker of genetically diverse high-grade endometrial stromal sarcoma, including tumors exhibiting variant morphology

ATM, BLM, and CDH1 gene co-mutations in a high-grade endometrial stromal sarcoma patient with multiple abdominal cavity metastases: a case report and literature review

BACKGROUND

High-grade endometrial stromal sarcoma (HG-ESS) is a rare malignant tumor with poor prognosis. To overcome the limitations of current treatment for advanced patients, the intervention of targeted drug therapy is urgently needed.

CASE PRESENTATION

A 74-year-old married woman who presented with abdominal distension and lower abdominal pain was admitted to Hebei General Hospital. After surgery, immunohistochemical staining revealed a malignant tumor which was consistent with HG-ESS. Tumor recurrence occurred 2 months after surgery. Then the patient underwent chemotherapy with two courses but responded poorly. Subsequently we observed ATM, BLM, and CDH1 co-mutations by Next Generation Sequencing (NGS). Then the patient received pamiparib, which resulted in a 10-month progression-free survival (PFS) and is now stable with the administration of sintilimab in combination with pamiparib and anlotinib.

CONCLUSIONS

Due to the successful use of poly ADP-ribose polymerase inhibitor (PARPi) on HG-ESS, we suggest that the selection of effective targeted drugs combined with anti- programmed death-1 (PD-1) drug therapy based on genetic testing may become a new option for the treatment of homologous repair deficient (HR-deficient) HG-ESS.

Diagnostic Value of Combined BCOR, Cyclin D1, and CD10 in Differentiating Endometrial Stromal Sarcoma From Other Uterine Spindle cell Lesions

Uterine spindle cell lesions share a dilemmatic overlapped features that needed to be addressed by the pathologist to reach a conclusive accurate diagnosis for its prognostic value and different management decisions. Usage of combined IHC panel can be an aiding guiding tool in this context. The aim of this study is to evaluate the diagnostic value of combined BCOR, Cyclin D1, and CD10 IHC panel in differentiating endometrial stromal sarcoma from other uterine spindle cell lesions. This study included 60 cases categorized into endometrial stromal sarcoma group (ESS) (12 cases high-grade endometrial stromal sarcoma [HGESS] and 18 cases low-grade endometrial stromal sarcoma [LGESS]), malignant uterine spindle cell lesions group (5 cases adenosarcoma [AS], 6 cases leiomyosarcoma [LS], 4 cases carcinosarcoma [CS]), and benign uterine lesions group (5 cases endometrial stromal nodule [ESN], 5 cases leiomyoma, and 5 cases adenomyosis). IHC staining procedure and evaluation for BCOR, Cyclin D1, and CD10 was performed on all studied cases. BCOR IHC staining was positive in all HGESS (12/12) of ESS group cases, with diffuse pattern in 75% of cases. BCOR-diffuse staining pattern was not recorded in any of LGESS (0/18), malignant mesenchymal lesions group (0/15), and also benign lesions group (0/15). Cyclin D1 positivity was observed only in HGESS cases, in parallel with positive-BCOR expression. On the contrary, CD10 was negatively expressed in all HGESS and positive in all LGESS, ESN, and adenomyosis cases. A specificity of 100% and sensitivity of 75% were recorded in differentiating HGESS from malignant mesenchymal lesions (including LMS, AS, and CS) and also HGESS from LGESS when using the combined panel BCOR+ve D/Cyclin D1+ve / CD10-ve, considering only the BCOR-diffuse staining pattern. In conclusion, BCOR+ve D/Cyclin D1+ve/CD10-ve as a combined panel is 100% specific and with lesser sensitivity in diagnosing HGESS as well as differentiating it from LGESS and other malignant uterine spindle cell lesions.

PLAG1-Rearranged Uterine Sarcomas: A Study of 11 Cases Showing a Wide Phenotypical Spectrum Not Limited to Myxoid Leiomyosarcoma-like Morphology

PLAG1 gene fusions were recently identified in a subset of uterine myxoid leiomyosarcomas (M-LMS). However, we have encountered cases of PLAG1-rearranged uterine sarcomas lacking M-LMS-like morphology and/or any expression of smooth muscle markers. To better characterize their clinicopathologic features, we performed a multiinstitutional search that yielded 11 cases. The patients ranged in age from 34 to 72 years (mean, 57 years). All tumors arose in the uterine corpus, ranging in size from 6.5 to 32 cm (mean, 15 cm). The most common stage at presentation was pT1b (n = 6), and 3 cases had stage pT1 (unspecified), and 1 case each presented in stages pT2a and pT3b. Most were treated only with hysterectomy and adnexectomy. The follow-up (range, 7-71 months; median, 39 months) was available for 7 patients. Three cases (7-21 months of follow-up) had no evidence of disease. Three of the 4 remaining patients died of disease within 55 to 71 months, while peritoneal spread developed in the last patient, and the patient was transferred for palliative care at 39 months. Morphologically, the tumors showed a high intertumoral and intratumoral heterogeneity. M-LMS-like and epithelioid leiomyosarcoma-like morphology were present in 3 and 5 primary tumors, respectively, the remaining mostly presented as nondescript ovoid or spindle cell sarcomas. Unusual morphologic findings included prominently hyalinized stroma (n = 3), adipocytic differentiation with areas mimicking myxoid liposarcoma (n = 2), osteosarcomatous differentiation (n = 1), and undifferentiated pleomorphic sarcoma-like areas (n = 1). The mitotic activity ranged from 3 to 24 mitoses per 10 high-power fields (mean, 9); 3 of 10 cases showed necrosis. In 3 of 11 cases, no expression of smooth muscle actin, h-caldesmon, or desmin was noted, whereas 5 of 5 cases expressed PLAG1. By RNA sequencing, the following fusion partners were identified: PUM1, CHCHD7 (each n = 2), C15orf29, CD44, MYOCD, FRMD6, PTK2, and TRPS1 (each n = 1). One case only showed PLAG1 gene break by fluorescence in situ hybridization. Our study documents a much broader morphologic spectrum of PLAG1-rearranged uterine sarcomas than previously reported, encompassing but not limited to M-LMS-like morphology with occasional heterologous (particularly adipocytic) differentiation. As it is currently difficult to precisely define their line of differentiation, for the time being, we suggest using a descriptive name "PLAG1-rearranged uterine sarcoma."

[Diagnosis of uterine sarcomas and rare uterine mesenchymal tumours with malignant potential. Guidelines of the French Sarcoma Group and Rare Gynaecological Tumours]

The landscape of uterine sarcomas is becoming more complex with the description of new entities associated with recurrent driver molecular alterations. Uterine sarcomas, in analogy with soft tissue sarcomas, are distinguished into complex genomic and simple genomic sarcomas. Leiomyosarcomas and undifferentiated uterine sarcomas belong to complex genomic sarcomas group. Low-grade and high-grade endometrial stromal sarcomas, other rare tumors associated with fusion transcripts (such as NTRK, PDGFB, ALK, RET ROS1) and SMARCA4-deficient uterine sarcoma are considered simple genomic sarcomas. The most common uterine sarcoma are first leiomyosarcoma and secondly endometrial stromal sarcomas. Three different histological subtypes of leiomyosarcoma (fusiform, myxoid, epithelioid) are identified, myxoid and epithelioid leiomyosarcoma being more aggressive than fusiform leiomyosarcoma. The distinction between low-grade and high-grade endometrial stromal sarcoma is primarily morphological and immunohistochemical and the detection of fusion transcripts can help the diagnosis. Uterine PEComa is a rare tumor, which is distinguished into borderline and malignant, according to a risk assessment algorithm. Embryonal rhabdomyosarcoma of the uterine cervix is more common in children but can also occur in adult women. Embryonal rhabdomyosarcoma of the uterine cervix is almost always DICER1 mutated, unlike that of the vagina which is wild-type DICER1, and adenosarcoma which can be DICER1 mutated but with less frequency. Among the emerging entities, sarcomas associated with fusion transcripts involving the NTRK, ALK, PDGFB genes benefit from targeted therapy. The integration of molecular data with histology and clinical data allows better identification of uterine sarcomas in order to better treat them.

An Unusual Endometrial Stromal Neoplasm With JAZF1-BCORL1 Rearrangement

Endometrial stromal tumors represent the second most common category of uterine mesenchymal tumors. Several different histologic variants and underlying genetic alterations have been recognized, one such being a group associated with BCORL1 rearrangements. They are usually high-grade endometrial stromal sarcomas, often associated with prominent myxoid background and aggressive behavior. Here, we report an unusual endometrial stromal neoplasm with JAZF1-BCORL1 rearrangement and briefly review the literature. The neoplasm formed a well-circumscribed uterine mass in a 50-yr-old woman and had an unusual morphologic appearance that did not warrant a high-grade categorization. It was characterized by a predominant population of epithelioid cells with clear to focally eosinophilic cytoplasm growing in interanastomosing cords and trabeculae set in a hyalinized stroma as well as nested and fascicular growths imparting focal resemblance to a uterine tumor resembling ovarian sex-cord tumor, PEComa, and a smooth muscle neoplasm. A minor storiform growth of spindle cells reminiscent of the fibroblastic variant of low-grade endometrial stromal sarcoma was also noted but conventional areas of low-grade endometrial stromal neoplasm were not identified. This case expands the spectrum of morphologic features seen in endometrial stromal tumors, especially when associated with a BCORL1 fusion and highlights the utility of immunohistochemical and molecular techniques in the diagnosis of these tumors, not all of which are high grade.

Soft tissue sarcoma with ZC3H7B::BCOR fusion in a male mimicking low-grade fibromyxoid sarcoma - A case report

Diagnosis of soft tissue tumors is often challenging, given the large number of entities, often with non-specific or overlapping morphology. Although morphology still plays an important part in diagnostic process, additional studies including immunohistochemistry and molecular genetics are often needed to arrive at correct diagnosis. We report a case of 61-year-old male with subcutaneous tumor in right hip area, that was surgically removed. The tumor was composed of uniform bland spindle cells in mild to moderately cellular myxoid nodules, with limited areas of collagenization and the diagnosis of low grade fibromyxoid sarcoma was made. The tumor recurred 3 years after the initial diagnosis and the new sample showed a high-grade round cell sarcoma with limited residual low-grade areas and non-specific immunoprofile after extended immunohistochemical work-up. Molecular analysis demonstrated ZC3H7B::BCOR fusion. Sarcomas with ZC3H7B::BCOR fusion occurring outside of uterus are exceedingly rare. A comprehensive review of previously published cases and a short discussion about classification of the entity is provided, together with data about morphology and immunoprofile of the lesions. The case also underscores the necessity of extended work up of soft tissue tumors with unusual immunohistochemical or morphological features in order to accurately assess their biological potential.

Expanding the Clinical Utility of Targeted RNA Sequencing Panels beyond Gene Fusions to Complex, Intragenic Structural Rearrangements

Gene fusions are a form of structural rearrangement well established as driver events in pediatric and adult cancers. The identification of such events holds clinical significance in the refinement, prognostication, and provision of treatment in cancer. Structural rearrangements also extend beyond fusions to include intragenic rearrangements, such as internal tandem duplications (ITDs) or exon-level deletions. These intragenic events have been increasingly implicated as cancer-promoting events. However, the detection of intragenic rearrangements may be challenging to resolve bioinformatically with short-read sequencing technologies and therefore may not be routinely assessed in panel-based testing. Within an academic clinical laboratory, over three years, a total of 608 disease-involved samples (522 hematologic malignancy, 86 solid tumors) underwent clinical testing using Anchored Multiplex PCR (AMP)-based RNA sequencing. Hematologic malignancies were evaluated using a custom Pan-Heme 154 gene panel, while solid tumors were assessed using a custom Pan-Solid 115 gene panel. Gene fusions, ITDs, and intragenic deletions were assessed for diagnostic, prognostic, or therapeutic significance. When considering gene fusions alone, we report an overall diagnostic yield of 36% (37% hematologic malignancy, 41% solid tumors). When including intragenic structural rearrangements, the overall diagnostic yield increased to 48% (48% hematologic malignancy, 45% solid tumor). We demonstrate the clinical utility of reporting structural rearrangements, including gene fusions and intragenic structural rearrangements, using an AMP-based RNA sequencing panel.

Evaluation of Lineage/Site-specific Nuclear Immunohistochemical Markers SATB2, Cyclin D1, SALL4, and BCOR in High-grade Endometrial Carcinomas

Poorly differentiated malignant neoplasms involving the gynecologic tract routinely include a poorly differentiated endometrial carcinoma (EC) in the differential diagnosis. Some nuclear lineage/site-specific immunohistochemical markers are utilized in this diagnostic setting including SATB2, cyclin D1, SALL4, and BCOR, but their specificity and use in small samples are not clear across the spectrum of ECs. Cases of undifferentiated/dedifferentiated endometrial carcinomas (UEC/DDEC), clear cell carcinoma (CCC), uterine serous carcinoma (USC), FIGO grade 3 endometrial endometrioid carcinoma (EEC), and uterine carcinosarcoma (UCS) were identified and diagnoses confirmed. Whole-section immunohistochemical stains for SATB2, cyclin D1, SALL4, BCOR, and PAX8 were performed. A total of 113 cases were utilized: 15 CCC, 26 EEC, 19 UCS, 22 USC, and 31 UEC/DDEC. Cases were distributed across both low (49%) and high (51%) FIGO clinical stages. SATB2 was expressed by UCS (8/19, 42%), EEC (10/26, 38%), UEC/DDEC (11/30, 37%), and USC (6/22, 27%). Cyclin D1 was expressed by EEC (24/26, 92%), USC (17/22, 77%), UEC/DDEC (15/20 EEC component, 75%; 22/30 UEC, 73%), UCS (10/16 carcinoma, 63%; 11/19 sarcoma, 58%), and CCC (8/15, 53%). SALL4 was expressed most frequently by UEC/DDEC (12/30, 40%), but also USC (7/22, 32%), EEC (5/26, 19%), and UCS (4/16 carcinoma, 25%; 3/19 sarcoma, 16%). BCOR was expressed at low levels in 2 USC, 2 UEC/DDEC, and 2 UCS. PAX8 was generally positive but showed lower expression in UEC/DDEC (17/30, 57%) and in the sarcomatous portions of UCS (6/19, 32%). SATB2, cyclin D1, SALL4, and BCOR stain variable numbers of poorly-differentiated EC and must be carefully interpreted within morphologic and clinical context.

Endometrial stromal tumors of the uterus: Epidemiology, pathological and biological features, treatment options and clinical outcomes

Endometrial stromal tumors (EST) are uterine mesenchymal tumors, which histologically resemble endometrial stroma of the functioning endometrium. The majority of EST are malignant tumors classified as low-grade endometrial stromal sarcoma (LG-ESS), high-grade endometrial stromal sarcoma (HG-ESS), and undifferentiated uterine sarcoma (UUS). Overall, ESTs are rare malignancies, with an annual incidence of approximately 0.30 per 100'000 women, mainly affecting peri- or postmenopausal women. The most common genetic alteration identified in LG-ESS is the JAZF1-SUZ12 rearrangement, while t(10;17)(q23,p13) translocation and BCOR gene abnormalities characterize two major subtypes of HG-ESS. The absence of specific genetic abnormalities is the actual hallmark of UUS. Unlike HG-ESSs, LG-ESSs usually express estrogen and progesterone receptors. Total hysterectomy without morcellation and bilateral salpingo-oophorectomy (BSO) is the first-line treatment of early-stage LG-ESS. Ovarian preservation, fertility-sparing treatment, and adjuvant hormonal therapy ± radiotherapy may be an option in selected cases. In advanced or recurrent LG-ESS, surgical cytoreduction followed by hormonal treatment, or vice versa, are acceptable treatments. The standard treatment for apparently early-stage HG-ESS and UUS is total hysterectomy without morcellation with BSO. Ovarian preservation and adjuvant chemotherapy ± radiotherapy may be an option. In advanced or recurrent HG-ESS, surgical cytoreduction and neoadjuvant or adjuvant chemotherapy can be considered. Alternative treatments, including biological agents and immunotherapy, are under investigation. LG-ESSs are indolent tumor with a 5-year overall survival (OS) of 80-100% and present as stage I-II at diagnosis in two third of patients. HG-ESSs carry a poor prognosis, with a median OS ranging from 11 to 24 months, and 70% of patients are in stage III-IV at presentation. UUS median OS ranges from 12 to 23 months and, at diagnosis, 70% of patients are in stage III-IV. The aim of this review is to assess the clinical, pathological, and biological features and the therapeutic options for malignant ESTs.

Uterine sarcomas: clinical practice guidelines for diagnosis, treatment, and follow-up, by Spanish group for research on sarcomas (GEIS)

Uterine sarcomas are very infrequent and heterogeneous entities. Due to its rarity, pathological diagnosis, surgical management, and systemic treatment are challenging. Treatment decision process in these tumors should be taken in a multidisciplinary tumor board. Available evidence is low and, in many cases, based on case series or clinical trials in which these tumors have been included with other soft tissue sarcoma. In these guidelines, we have tried to summarize the most relevant evidence in the diagnosis, staging, pathological disparities, surgical management, systemic treatment, and follow-up of uterine sarcomas.

Case Report: A case of COL1A1–PDGFB fusion uterine sarcoma at cervix and insights into the clinical management of rare uterine sarcoma

COL1A1–PDGFB gene fusion uterine sarcoma is an especially rare malignant mesenchymal tumor that was previously classified as an undifferentiated uterine sarcoma due to the lack of specific features of differentiation. Till now, only five cases have been reported, and here we presented another case recently diagnosed in a Chinese woman who had vaginal bleeding. She presented with a cervical mass at the anterior lip of the cervix invading the vagina and was treated with laparoscopic total hysterectomy plus bilateral salpingo-oophorectomy (TH+BSO) and partial vaginal wall resection with the final pathology of COL1A1–PDGFB fusion uterine sarcoma. Our aim is to emphasize the importance of differential diagnosis of this rare tumor, as early precise diagnosis may allow patients to benefit from the targeted therapy imatinib. This article also serves as further clinical evidence of this disease, serving to increase clinical awareness of this rare sarcoma to avoid misdiagnosis.

High-grade neuroepithelial tumor with EP300::BCOR fusion and negative BCOR immunohistochemical expression: a case report

In the World Health Organization tumor classification (fifth edition), central nervous system (CNS) tumors with BCOR internal tandem duplications have been recognized as a new tumor type. Some recent studies have reported CNS tumors with EP300::BCOR fusions, predominantly in children and young adults, expanding the spectrum of BCOR-altered CNS tumors. This study reports a new case of high-grade neuroepithelial tumor (HGNET) with an EP300::BCOR fusion in the occipital lobe of a 32-year-old female. The tumor displayed anaplastic ependymoma-like morphologies characterized by a relatively well-circumscribed solid growth with perivascular pseudorosettes and branching capillaries. Immunohistochemically, OLIG2 was focally positive and BCOR was negative. RNA sequencing revealed an EP300::BCOR fusion. The Deutsches Krebsforschungszentrum DNA methylation classifier (v12.5) classified the tumor as CNS tumor with BCOR/BCORL1 fusion. The t-distributed stochastic neighbor embedding analysis plotted the tumor close to the HGNET with BCOR alteration reference samples. BCOR/BCORL1-altered tumors should be included in the differential diagnosis of supratentorial CNS tumors with ependymoma-like histological features, especially when they lack ZFTA fusion or express OLIG2 even in the absence of BCOR expression. Analysis of published CNS tumors with BCOR/BCORL1 fusions revealed partly overlapping but not identical phenotypes. Further studies of additional cases are required to establish their classification.

BCOR-Rearranged Sarcoma of the Tonsil

A tonsillar mass in a young patient with no medical issues routinely presents as an infectious process. Practitioners must maintain a broad differential if diagnostic testing does not support an infection. Neoplasm must be excluded. Otolaryngologists must consider malignancies other than squamous cell carcinoma, the most common oropharyngeal malignancy, and lymphoma. Rare tumors, such as sarcomas, must also be considered. Otolaryngologists must be familiar with the proper management of rare oropharyngeal malignancies.

High-grade endometrial stromal sarcoma-like' sarcoma in male: Does it exist? A case report and review of the literature

We report an exceptional case of an undifferentiated round and spindle cell sarcoma, occurring in the periprostatic region of a 54-year-old male, with a 'high-grade endometrial stromal sarcoma-like' (HG-ESS) morphology and harboring a ZC3H7B::BCOR gene fusion identified by RNA-based next-generation sequencing. In this report, we describe the striking overlap of morphologic, immunohistochemical and molecular features of this current case and previously reported similar cases with ZC3H7B::BCOR fusion-positive HG-ESS, and discuss the differential diagnosis and possible pathogenesis of this unusual entity.

ZC3H7B-BCOR High-Grade Endometrial Stromal Sarcoma with a Mucoid Grossly Feature: A Case Report and Literature Review

We report on a 50-year-old postmenopausal woman who presented with abnormal uterine bleeding and pelvic pain due to a uterine solid mass grew from the uterine fundus to the cervix and with so far undescribed obviously gelatinous grossly change, which was suspected of myxoid leiomyosarcoma in intraoperative diagnosis. Morphologically, the tumor cells displayed haphazard fascicles of uniform mild-to-moderate heteromorphic spindle cell component with significant and abundant myxoid stroma, forming signet ring cells and microcysts. Immunohistochemically, the tumour cells were diffusely positivefor CD10 and cyclin D1 and negative for Desmin and SMA, but the expression of BCOR staining was not present. The FISH study showed a positive BCOR gene break probe, and the RNA sequencing revealed an identified reciprocal fusion gene ZC3H7B-BCOR. The case was finally diagnosed as ZC3H7B-BCOR high-grade endometrial stromal sarcoma. Tumor recurrence occurred rapidly on the pelvic peritoneal and vaginal 2 months after resection. In conclusion, these findings further support ZC3H7B-BCOR HGESS has a poor prognosis and molecular testing of uterine mesenchymal tumors with myxoid matrix and unusual grossly presentation is recommended to avoid misdiagnosis.

Uterine sarcomas and rare uterine mesenchymal tumors with malignant potential. Diagnostic guidelines of the French Sarcoma Group and the Rare Gynecological Tumors Group

The landscape of uterine sarcomas is becoming increasingly complex with the description of new entities associated with recurrent molecular alterations. Uterine sarcomas, as well as soft tissue sarcomas, can be distinguished into complex genomic sarcomas and simple genomic sarcomas. Leiomyosarcoma and pleomorphic type undifferentiated uterine sarcoma belong to the first group. Low-grade and high-grade endometrial stromal sarcomas, NTRK, COL1A1::PDGFB, ALK, RET, ROS1 associated sarcomas, and SMARCA4 deficient uterine sarcoma belong to the second group. Leiomyosarcoma is the most common uterine sarcoma followed by endometrial stromal sarcomas. Three different histologic subtypes of leiomyosarcomas are recognized with distinct diagnostic criteria and different clinical outcomes, the myxoid and epithelioid leiomyosarcomas being even more aggressive than the fusiform type. The distinction between low-grade and high-grade endometrial stromal sarcoma is based first on morphology and immunohistochemistry. The detection of fusion transcripts helps in the diagnosis. Definitely recognized as a separate entity, uterine PEComa is a rare tumor whose diagnostic criteria are being recently defined. Uterine PEComa has a specific algorithm stratifying the tumors into uncertain malignant potential and malignant tumors. Embryonal rhabdomyosarcomas of the uterine cervix are not restricted to children but can also be observed in adult women and are almost always DICER1 mutated, unlike embryonal rhabdomyosarcoma of the vagina which are DICER1wild-type, and adenosarcoma which can be DICER1 mutated but with less frequency. As sarcomas associated with fusion transcripts involving the NTRK, ALK, COL1A1::PDGFB genes can benefit from targeted therapy, systematic detection are now relevant especially for patients with high risk of relapse or in recurrent setting. The integration of molecular data with dedicated expert pathology review for histology and clinical data allows better identification of uterine sarcomas in order to better treat them.

Epigenetic Features in Uterine Leiomyosarcoma and Endometrial Stromal Sarcomas: An Overview of the Literature

There is a consensus that epigenetic alterations play a key role in cancer initiation and its biology. Studies evaluating the modification in the DNA methylation and chromatin remodeling patterns, as well as gene regulation profile by non-coding RNAs (ncRNAs) have led to the development of novel therapeutic approaches to treat several tumor types. Indeed, despite clinical and translational challenges, combinatorial therapies employing agents targeting epigenetic modifications with conventional approaches have shown encouraging results. However, for rare neoplasia such as uterine leiomyosarcomas (LMS) and endometrial stromal sarcomas (ESS), treatment options are still limited. LMS has high chromosomal instability and molecular derangements, while ESS can present a specific gene fusion signature. Although they are the most frequent types of “pure” uterine sarcomas, these tumors are difficult to diagnose, have high rates of recurrence, and frequently develop resistance to current treatment options. The challenges involving the management of these tumors arise from the fact that the molecular mechanisms governing their progression have not been entirely elucidated. Hence, to fill this gap and highlight the importance of ongoing and future studies, we have cross-referenced the literature on uterine LMS and ESS and compiled the most relevant epigenetic studies, published between 2009 and 2022.

Paediatric BCOR ‐associated sarcomas with a novel long spliced internal tandem duplication of BCOR exon 15

Clear cell sarcoma of the kidney (CCSK) and primitive myxoid mesenchymal tumour of infancy (PMMTI) are paediatric sarcomas that most commonly harbour internal tandem duplications (ITDs) of exon 15 of the BCOR gene, in the range of 87–114 base pairs (bp). Some cases, instead, have BCOR‐CCNB3 or YWHAE‐NUTM2 gene fusions. About 10% of cases lack any of these genetic alterations when tested by standard methods. Two cases of CCSK and one PMMTI lacking the aforementioned mutations were analysed using Archer FusionPlex technology. Two related BCOR exon 15 RNA transcripts with ITDs of lengths 388 and 96 bp were detected in each case; only the 388 bp transcript was identified when genomic DNA was sequenced. In silico analysis of this transcript revealed acceptor and donor splice sites indicating that, at the RNA level, the 388‐bp transcript was likely spliced to form the 96‐bp transcript. The results were confirmed by Sanger sequencing using primers targeting the ITD breakpoint. This novel and unusually long ITD segment is difficult to identify by DNA sequencing using typical primer design strategies flanking entire duplicated segments because it exceeds the typical read lengths of most sequencing platforms as well as the usual fragment lengths obtained from formalin‐fixed paraffin‐embedded material. As diagnosis of CCSK and PMMTI may be challenging by morphology and immunohistochemistry alone, it is important to identify mutations in these cases. Knowledge of this novel BCOR ITD is important in relation to primer design for detection by sequencing, and using RNA versus DNA for sequencing.

BCOR Internal Tandem Duplication Associated Uterine Sarcoma: Expanding the Clinicopathologic Spectrum

The diagnosis of high-grade endometrial stromal sarcoma has become more refined following molecular characterization of these tumors. Recently BCOR internal tandem duplications (ITD) have been identified in a small number of high-grade endometrial stromal sarcoma. Here we present an additional case of this rare entity in a young woman in her late teens. She presented with menorrhagia and underwent resection of 2 uterine lesions. The tumor was a spindle cell neoplasm composed of long fascicles with low to moderate cellularity, mild to moderate cytologic atypia, and up to 2 mitotic figures per 10 high power fields. Necrosis was not identified. Immunohistochemical stains showed the tumor to be positive for cyclin D1 in >50% of tumor cells, focally positive for CD10, and negative for SMA, desmin, h-caldesmon, and ALK1. BCOR ITD was confirmed by polymerase chain reaction with subsequent Sanger sequencing. Clues to the diagnosis of BCOR ITD uterine sarcoma include young patient age, uniform nuclear features, and diffuse positivity for cyclin D1. These features should prompt further molecular interrogation for definitive diagnosis, which is important for prognostication.

Endometrial Stromal Sarcomas With BCOR Internal Tandem Duplication and Variant BCOR/BCORL1 Rearrangements Resemble High-grade Endometrial Stromal Sarcomas With Recurrent CDK4 Pathway Alterations and MDM2 Amplifications

The distinction between low-grade and high-grade endometrial stromal sarcomas (LGESS, HGESS) is increasingly defined by genetics. Recently, variant genomic alterations involving BCOR or BCORL1 have been reported in endometrial stromal sarcoma (ESS), although it remains unclear whether these justify a diagnosis of LGESS or HGESS. In this study, we describe clinicopathologic and molecular features of ESS with such alterations to help clarify their classification in the spectrum of ESS. We collected a cohort of 13 ESS harboring variant alteration involving BCOR (6 with internal tandem duplication, 1 with EP300::BCOR fusion, 1 with BCOR::LPP fusion) and BCORL1 ( 4 with JAZF1::BCORL1 fusion, 1 with EPC1::BCORL1 fusion). The median patient age at primary diagnosis was 51 years (range: 18 to 70 y). Median tumor size at primary diagnosis was 9.3 cm (range: 4.5 to 21 cm), and extrauterine disease spread (stage IIIB-C) was present in 27%. The tumors were composed of round to spindled cells with cellularity and cytologic atypia ranging from mild to marked and a median mitotic count of 18/10 HPFs (range: 2 to 85/10 HPFs). At least focally myopermeative growth was noted in 8/8 assessable cases. Of 12 patients with follow-up data (median: 25 mo), 4 patients died of disease and 3 were alive with recurrent disease. Unsupervised hierarchical clustering of DNA methylation data together with a large cohort of uterine mesenchymal tumors that included YWHAE::NUTM2 and Z C3H7B::BCOR HGESS and molecularly confirmed LGESS revealed a common methylation signature for all ESS with variant BCOR and BCORL1 alterations and HGESS with YWHAE::NUTM2 and ZC3H7B::BCOR gene fusion. Copy number analysis revealed amplifications of CDK4 and MDM2 , as well as homozygous deletions of CDKN2A/B and NF1 in a subset of tumors. Our results indicate that ESS with BCOR internal tandem duplication and variant BCOR and BCORL1 rearrangements clinically and molecularly resemble conventional HGESS.

Update on Uterine Mesenchymal Neoplasms

This review focuses on recent advances in epithelioid and myxoid uterine mesenchymal neoplasms, a category of tumors whereby diagnostic criteria have been rapidly evolving due to advances in molecular testing. Pertinent clinicopathological and molecular features are highlighted for perivascular epithelioid cell tumors, uterine tumors resembling ovarian sex cord tumors, BCOR/BCORL1-altered high-grade endometrial stromal sarcomas, and inflammatory myofibroblastic tumors. Novel developments in epithelioid and myxoid leiomyosarcomas are briefly discussed, and differential diagnoses with key diagnostic criteria are provided for morphologic mimickers.

High-grade Endometrial Stromal Sarcoma: Morphologic and Clinical Features, the Role of Immunohistochemistry and Fluorescence in Situ Hybridization in Diagnosis

Introduction. High-grade endometrial stromal sarcomas (HGESS) are rare malignant mesenchymal tumors of the uterus with aggressive poor clinical outcome, which frequently exhibit YWHAE::NUTM2 and ZC3H7B::BCOR fusions. In this study, we aimed to investigate HGESSs with YWHAE and BCOR translocations through our archive materials, and to identify morphological, immunohistochemical and molecular features of these tumors. We also assessed the diagnostic value of BCOR immunohistochemistry (IHC) in HGESSs, low-grade endometrial stromal sarcomas (LGESS) and uterine leiomyosarcomas. Methods. One hundred fifty-one uterine sarcomas diagnosed between 2000-2019 were reevaluated, and tumors of 39 patients with specific features were included in the study. Fluorescence in situ hybridization (FISH) studies using YWHAE and BCOR break-apart probes and BCOR IHC were performed. BCOR IHC was also performed in 20 leiomyosarcomas and 19 LGESSs. Results. In six HGESSs, translocations involving YWHAE or BCOR were detected. Five tumors showed high-grade morphology and revealed YWHAE translocation. One HGESS with myxoid morphology revealed BCOR translocation. In immunohistochemistry, three (3/4) YWHAE translocated HGESSs showed BCOR expression. However, the BCOR translocated HGESS was BCOR negative. The study showed that all LGESSs were immunohistochemically negative with BCOR. Although 15% (3/20) leiomyosarcomas reveal focal weak-moderate BCOR expression. Conclusion. BCOR IHC is a useful marker to distinguish LGESS from HGESS. A small percentage of uterine leiomyosarcomas reveal BCOR expression; however, it is not as diffuse and strong as in HGESSs. Strong and diffuse BCOR IHC expression is highly suggestive for HGESS. The diagnosis of HGESS should be supported by molecular studies such as FISH.

High-Grade Endometrial Stromal Sarcoma: Molecular Alterations and Potential Immunotherapeutic Strategies

Endometrial stromal tumor (EST) is an uncommon and unusual mesenchymal tumor of the uterus characterized by multicolored histopathological, immunohistochemical, and molecular features. The morphology of ESTs is similar to normal endometrial stromal cells during the proliferative phase of the menstrual cycle. ESTs were first classified into benign and malignant based on the number of mitotic cells. However, recently WHO has divided ESTs into four categories: endometrial stromal nodules (ESN), undifferentiated uterine sarcoma (UUS), low-grade endometrial stromal sarcoma (LG-ESS), and high-grade endometrial stromal sarcoma (HG-ESS). HG-ESS is the most malignant of these categories, with poor clinical outcomes compared to other types. With advances in molecular biology, ESTs have been further classified with morphological identification. ESTs, including HG-ESS, is a relatively rare type of cancer, and the therapeutics are not being developed compared to other cancers. However, considering the tumor microenvironment of usual stromal cancers, the advance of immunotherapy shows auspicious outcomes reported in many different stromal tumors and non-identified uterine cancers. These studies show the high possibility of successful immunotherapy in HG-ESS patients in the future. In this review, we are discussing the background of ESTs and the BCOR and the development of HG-ESS by mutations of BCOR or other related genes. Among the gene mutations of HG-ESSs, BCOR shows the most common mutations in different ways. In current tumor therapies, immunotherapy is one of the most effective therapeutic approaches. In order to connect immunotherapy with HG-ESS, the understanding of tumor microenvironment (TME) is required. The TME of HG-ESS shows the mixture of tumor cells, vessels, immune cells and non-malignant stromal cells. Macrophages, neutrophils, dendritic cells and natural killer cells lose their expected functions, but rather show pro-tumoral functions by the matricellular proteins, extracellular matrix and other complicated environment in TME. In order to overcome the current therapeutic limitations of HG-ESS, immunotherapies should be considered in addition to the current surgical strategies. Checkpoint inhibitors, cytokine-based immunotherapies, immune cell therapies are good candidates to be considered as they show promising results in other stromal cancers and uterine cancers, while less studied because of the rarity of ESTs. Based on the advance of knowledge of immune therapies in HG-ESS, the new strategies can also be applied to the current therapies and also in other ESTs.

[Endometrial and other rare uterine sarcomas : Diagnostic aspects in the context of the 2020 WHO classification]

Uterine sarcomas are a heterogeneous group of rare malignancies. Mostly (40-50%), they are leiomyosarcomas, followed by endometrial stromal sarcomas (ESS), low-grade (LG) and high-grade (HG), as well as undifferentiated sarcoma of the uterus (UUS) and adenosarcomas (AS). Other, non-organ-specific tumours such as NTRK-rearranged spindle cell neoplasia, perivascular epithelioid cell tumour (PEComa) and inflammatory myofibroblastic tumour (IMT) are extremely difficult to differentiate.In the most recent WHO classification, endometrial stromal tumours are subdivided as follows: benign, expansively growing endometrial stromal nodule (ESN) with sharp demarcation, the histologically similar-looking LG-ESS with infiltrative growth, the highly malignant HG-ESS and, as a diagnosis of exclusion, the highly aggressive UUS lacking specific lines of differentiation. LG-ESS can be differentiated from HG-ESS in most cases histomorphologically and immunohistochemically, but molecular investigations are necessary in individual cases. HG-ESS can be divided into 4 subtypes (YWHAE/NUTM2 fusion low-grade component, YWHAE/NUTM2 fusion high-grade component, ZC3H7B-BCOR fusion or BCOR-ITD) on the basis of molecular findings. Prognostically unfavourable factors in AS are severe sarcomatous overgrowth, deep myometrial invasion, high-grade histology and lymphatic vessel invasion. Tumours with NTRK fusion are immunohistochemically positive for S100 and TRK. PEComas express cathepsin K and HMB45, as well as TFE3 when translocation is present. Almost every IMT shows an alteration in the ALK gene In the case of overlapping morphology and simultaneous therapeutic and prognostic relevance, it is becoming increasingly important to verify or confirm the suspected histomorphological diagnosis by immunohistochemical and possibly molecular investigations.

A novel WWTR1 :: AFF2 fusion in an intra‐abdominal soft tissue sarcoma with associated endometriosis

Application of molecular testing in clinical practice has led to significant advances in the classification of soft tissue sarcomas. Despite remarkable progress, there are still challenging cases that remain unclassified. In this study, we present an unusual spindle cell sarcoma arising in the abdominal cavity of a 37-year-old female. An extensive panel of immunostains was nonspecific for a line of differentiation and the tumor was subjected to targeted RNA sequencing for further classification. The findings showed a novel WWTR1::AFF2 fusion, which was further confirmed by break-apart FISH analysis for WWTR1 gene rearrangement. The tumor was attached to the wall of sigmoid colon and showed a highly cellular proliferation of plump spindle to epithelioid cells arranged in intersecting fascicles. Areas of extensive endometriosis were identified adjacent to the tumor. The immunoprofile was significant for reactivity with desmin, calponin, WT-1, ER, and PR, while negative for CD10, SMA, caldesmon, pan-keratin, ALK, CD117, and S100. The patient is alive and well after 11 months of follow-up. The exact histogenesis of this sarcoma remains unclear, however, the presence of adjacent endometriosis and coexpression of WT1/ER/PR raises the possibility of an unusual endometrioid stromal sarcoma, occurring outside the GYN tract. Additional cases are needed to establish the recurrent potential of this fusion event and to better define its pathogenesis and clinical behavior.

Epithelioid Leiomyosarcoma of the Uterus: Modern Outcome-based Appraisal of Diagnostic Criteria in a Large Institutional Series

Epithelioid leiomyosarcoma of the uterus is rare and poorly understood. Herein, we characterize a large institutional series of epithelioid leiomyosarcomas aiming to define outcome-determinant diagnostic pathologic features. We also retrieved epithelioid smooth muscle tumors of unknown malignant potential and evaluated a consecutive cohort of leiomyomas for epithelioid subtypes. Of a total of 1177 uterine leiomyosarcomas, 81 (7%) were categorized as epithelioid after review. Epithelioid leiomyosarcoma was strictly defined as having round to polygonal cells with visible pink cytoplasm and round to ovoid nuclei in ≥50% of the tumor volume. Average age was 55 years (range: 26 to 81 y). Median tumor size was 11 cm; tumor was >5 cm in 93% of subjects; 47% were stage 1 at presentation. An infiltrative tumor border was observed, grossly and/or microscopically, in 89% of cases; necrosis was noted in 80%, and vascular invasion in 47%. Mitotic count in 2.4 mm2 (totalling 10 high-power fields, each field 0.55 mm in diameter) ranged from 3 to 100 (median: 26). All cases had moderate, severe or highly pleomorphic atypia. All cases had 2 or 3 of the following: necrosis, at least moderate atypia and ≥4 mitoses in 2.4 mm2. Immunohistochemistry revealed frequent expression of smooth muscle markers including SMA (96%), desmin (95%), and caldesmon (81%). HMB45 and Melan-A were negative in 92% and 100% of cases, respectively. Estrogen and progesterone receptors were expressed by 65% and 54% of tumors, respectively. Follow-up information was available in 68 subjects (median: 23 mo, range: 1 to 254); cancer-related death occurred in 63%, and an additional 15% had recurrent or metastatic disease at last follow-up. Disease-specific survival was shorter in epithelioid leiomyosarcoma patients (median: 44  mo; 35% at 5-y) than in a matched cohort of nonepithelioid leiomyosarcoma (median: 55 mo; 46% at 5-y) (P=0.03). Three epithelioid smooth muscle tumors of unknown malignant potential were evaluated, all <5 cm in size and with atypia and/or irregular borders but mitotic count below the threshold for malignancy. Two of these had follow-up available, which was uneventful. Of 142 consecutive leiomyomas assessed, none had epithelioid morphology as defined. Epithelioid leiomyosarcoma is an aggressive neoplasm, sometimes with a remarkably low mitotic count. In the setting of an epithelioid smooth muscle tumor of the uterus, we postulate that the diagnosis of malignancy is made in the presence of ≥2 of the following: moderate or severe atypia, ≥4 mitoses/2.4 mm2 and tumor cell necrosis. In their absence, the finding of tumor size ≥5 cm, vascular invasion, infiltrative edges or atypical mitoses should be treated with caution, and designation as of at least uncertain malignant potential is warranted.

JAZF1, YWHAE and BCOR gene translocation in primary extrauterine low-grade and high-grade endometrial stromal sarcomas

AIMS

JAZF1 translocation is the most common genetic change in low-grade (LG) endometrial stromal sarcoma (ESS), and YWHAE and BCOR translocations are common in high-grade (HG) ESS. Primary extrauterine ESS is rare, and there are limited data on molecular alterations in these tumours.

METHODS AND RESULTS

Cases of primary extrauterine ESS, comprising eight LG-ESS cases and five HG-ESS cases were collected. Haematoxylin and eosin and immunohistochemical staining were used to observe the histomorphology and analyse related protein expression. JAZF1, YWHAE and BCOR rearrangements were explored with fluorescence in-situ hybridisation (FISH). In LG-ESS, the tumour cells resembled normal proliferative-phase endometrial stromal cells; CD10, oestrogen receptor and progesterone receptor were expressed in all eight cases. In HG-ESS, the tumour cells had uniform HG round and/or spindle morphology, sometimes with an LG component; CD10 was fully expressed in one case and focally expressed in four cases; BCOR was expressed in all five cases, and cyclin D1 in four of five cases. FISH analysis showed JAZF1 translocation in one of eight LG-ESS cases (12.5%). YWHAE translocation occurred in four of five HG-ESS cases, with a positivity rate of 80%. BCOR translocation was absent in all five cases.

CONCLUSIONS

In extrauterine LG-ESS, the rate of JAZF1 rearrangement was significantly lower than in uterine LG-ESS. This result limited the value of JAZF1 translocation for diagnosis. YWHAE rearrangement is a common genetic change in extrauterine HG-ESS. Further studies are required to confirm these findings, especially in LG-ESS.

Discrepancies in pathological diagnosis of endometrial stromal sarcoma: a multi-institutional retrospective study from the Japanese Clinical Oncology Group

Endometrial stromal sarcoma (ESS) is a rare uterine malignancy that requires accurate pathological diagnosis for proper treatment. This study aimed to clarify the discrepancies in the pathological diagnosis of ESS and obtain practical clues to improve diagnostic accuracy. Between 2002 and 2015, 148 patients with low-grade ESS (LGESS), high-grade ESS (HGESS), undifferentiated endometrial sarcoma (UES), or undifferentiated uterine sarcoma (UUS) diagnosed at 31 institutions were included. We performed immunohistochemistry, real-time polymerase chain reaction for JAZF1-SUZ12 and YWHAE-NUTM2A/B, and break-apart fluorescent in situ hybridization for JAZF1, PHF1, and YWHAE. Central pathology review (CPR) was performed by six pathologists. After CPR, LGESS, HGESS, UES/UUS, and other diagnoses were confirmed in 72, 25, 16, and 31 cases, respectively. Diagnostic discrepancies were observed in 19.6% (18/92) of LGESS and 34% (18/53) of HGESS or UUS/UES. Adenosarcomas, endometrial carcinomas, carcinosarcomas, and leiomyosarcomas were common diagnostic pitfalls. JAZF1-SUZ12 transcript, PHF1 split signal, and YWHAE-NUTM2A/B transcript were mutually exclusively detected in 23 LGESS, 3 LGESS, and 1 LGESS plus 3 HGESS, respectively. JAZF1-SUZ12 and YWHAE-NUTM2A/B transcripts were detected only in cases with CPR diagnosis of LGESS or HGESS. The CPR diagnosis of LGESS, HGESS, and UUS was a significant prognosticator, and patients with LGESS depicted a favorable prognosis, while those with UUS showed the worst prognosis. Pathological diagnosis of ESS is often challenging and certain tumors should be carefully considered. The accurate pathological diagnosis with the aid of molecular testing is essential for prognostic prediction and treatment selection.

Solitary Fibrous Tumors of the Female Genital Tract: A Study of 27 Cases Emphasizing Nonvulvar Locations, Variant Histology, and Prognostic Factors

We report 27 solitary fibrous tumors of the female genital tract emphasizing nonvulvar locations, variant histology, and prognostic factors. The patients ranged from 25 to 78 years (most were over 40), and tumors occurred in the vulva (7), vagina (2), cervix (2), corpus (6), fallopian tube/paratubal soft tissue (5), and ovary (5). They ranged from 1.5 to 39 (mean=10.5) cm and were typically solid, but 4 were predominantly cystic. All had a haphazard arrangement of spindled to ovoid cells, with most demonstrating alternating cellular and hypocellular areas and prominent vessels, but 13 lacked hypocellular areas, and 7 had focal diffuse growth with inconspicuous vasculature. Other patterns included corded (8), fascicular (5), trabecular (1), and nested (1). Microcysts (6), myxoid background (8), hyalinization (8), lipomatous differentiation (2), and multinucleated cells (6) were also present, and 10 tumors had necrosis. Vasculature included thin-walled branching "staghorn" (27), thick-walled (7), and hyalinized vessels (5) or dilated anastomosing vascular channels (3). Nuclear atypia ranged from mild (19), moderate (7), to severe (1), and mitoses from 0 to 24/10 HPF (mean=4). STAT6 was positive in all 25 tumors tested. One tumor showed dedifferentiation; the remainder were classified as benign (19) or malignant (7) based on mitotic rate (univariate stratification model) and as low risk (14), intermediate risk (8), or high risk (4) based on the Demicco multivariate risk stratification score. Follow-up (median=23 mo) was available for 16 patients. Six tumors recurred (2 intermediate risk, 3 high risk, and the dedifferentiated tumor), 5 in the abdomen; the dedifferentiated tumor metastasized to the lung. Multivariate risk stratification was superior to univariate classification, as 5 "benign" tumors were reclassified as intermediate risk using the multivariate model; of these, 2 recurred, and 1 patient died of disease. Upper female genital tract tumors occurred in older patients, were larger, and more frequently classified as high risk compared with those of the lower tract. A trend toward increased cellularity was also seen in the upper tract tumors. Only size (P=0.04), necrosis (P=0.04), and Demicco score (P=0.01) independently correlated with recurrence. Female genital tract solitary fibrous tumors demonstrate a wide range of variant morphologies and occur in diverse sites in addition to the vulva. Tumors were often misdiagnosed as other neoplasms; thus, awareness of solitary fibrous tumors occurring at these sites is crucial in prompting staining for STAT6 to establish this diagnosis. The Demicco risk stratification system effectively predicts behavior.

MR Imaging of uterine sarcomas: a comprehensive review with radiologic-pathologic correlation

The aim of this article is to summarize the MRI features of each sarcoma subtype and to correlate them with its pathological findings. Literature review through PubMed/Medline database to identify relevant articles on uterine sarcomas, with a special emphasis on their MRI findings and pathological features. While several, more generalistic, MRI findings of a uterine tumour should raise suspicion for malignancy (including irregular contour, intra-tumoral necrosis/hemorrhage and low ADC values), some particular features may suggest their specific histological subtype such as the gross lymphovascular invasion associated with endometrial stromal sarcomas, the "bag of worms" appearance of the low-grade endometrial stromal sarcoma and the "lattice-like" aspect of adenosarcomas which results from the mixed composition of solid and multiseptated cystic components. Knowledge of the different histological uterine sarcoma subtypes, their specific MRI features and comprehension of their pathological background allows for a more confident diagnosis and may indicate the correct histological subtype.

New Aspects of Sarcomas of Uterine Corpus-A Brief Narrative Review

Sarcomas of the uterine corpus are rare malignant neoplasms, which are further classified into mesenchymal tumors, and mixed (epithelial plus mesenchymal) tumors. The main issues concerning these neoplasms are the small number of clinical trials, insufficient data from evidence-based medicine, insignificant interest from the pharmaceutical industry, all of which close a vicious circle. The low frequency of these malignancies implies insufficient experience in the diagnosis, hence incomplete surgical and complex treatment. Additionally, the rarity of these sarcomas makes it very difficult to develop clinical practice guidelines. Preoperative diagnosis, neoadjuvant and adjuvant chemoradiation, target and hormone therapies still raise many controversies. Disagreements about the role and type of surgical treatment are also often observed in medical literature. There are still insufficient data about the role of pelvic lymph node dissection and fertility-sparing surgery. Pathologists’ experience is of paramount importance for an accurate diagnosis. Additionally, genetics examinations become part of diagnosis in some sarcomas of the uterine corpus. Some gene mutations observed in uterine sarcomas are associated with different outcomes. Therefore, a development of molecular classification of uterine sarcomas should be considered in the future. In this review, we focus on the epidemiology, pathogenesis, pathology, diagnosis and treatment of the following sarcomas of the uterine corpus: leiomyosarcoma, low- and high-grade endometrial stromal sarcomas, undifferentiated sarcoma and adenosarcoma. Uterine carcinosarcomas are excluded as they represent an epithelial tumor rather than a true sarcoma.

EWSR1-WT1 gene fusions in neoplasms other than desmoplastic small round cell tumor: a report of three unusual tumors involving the female genital tract and review of the literature

Desmoplastic small round cell tumor (DSRCT) is a high-grade round cell sarcoma that typically arises in the abdominopelvic cavity of young males, co-expresses keratins and desmin, and carries a pathognomonic EWSR1-WT1 gene fusion. The EWSR1-WT1 gene fusion is generally considered specific for DSRCT, although there are two reports of this fusion in tumors otherwise lacking features of DSRCT. We report three female genital tract tumors with EWSR1-WT1 fusions but showing morphologic and immunohistochemical features incompatible with DSRCT. The tumors occurred in the uterine cervix, uterine corpus/ovaries, and vagina, respectively, of 46, 30, and 20-year-old women. Two tumors consisted of a sheet-like to fascicular proliferation of relatively uniform spindled to occasionally more epithelioid cells arrayed about thick-walled, hyalinized, and capillary-sized vessels, with distinctive areas of pseudovascular change, and absence of desmoplastic stroma. The third tumor resembled a monomorphic spindle cell sarcoma with necrosis. All had diffuse desmin and variable but more limited keratin expression, two of three expressed smooth muscle actin, and all were negative for h-caldesmon, CD10, estrogen receptor, myogenin, N-terminus WT-1, and S100 protein. One patient received neoadjuvant chemotherapy and radiation therapy followed by resection and is disease-free 42 months after diagnosis. Another patient was managed by resection only and is disease-free 9 months after initial diagnosis. The remaining patient recently underwent resection of multifocal pelvic disease. Comprehensive differential gene expression analysis on two tumors compared to two classic DSRCTs with known EWSR1-WT1 fusions resulted in 1726 genes that were differentially expressed (log2 fold change >2 or < -2) and statistically significant (FDR < 5%). In combination with previous reports, our findings suggest pleiotropy of the EWSR1-WT1 fusion is possible and not limited to DSRCT. Subsets of non-DSRCT EWSR1-WT1 positive tumors may represent discrete entities, but further study is necessary.

Embryonal rhabdomyosarcoma of the uterine corpus: a clinicopathological and molecular analysis of 21 cases highlighting a frequent association with DICER1 mutations

Herein we evaluated a series of 21 embryonal rhabdomyosarcomas of the uterine corpus (ucERMS), a rare neoplasm, to characterize their morphology, genomics, and behavior. Patients ranged from 27 to 73 (median 52) years and tumors from 4 to 15 (median 9) cm, with extrauterine disease noted in two. Follow-up (median 16 months) was available for 14/21 patients; nine were alive and well, four died of disease, and one died from other causes. Most tumors (16/21) showed predominantly classic morphology, comprised of alternating hyper- and hypocellular areas of primitive small cells and differentiating rhabdomyoblasts in a loose myxoid/edematous stroma. A cambium layer was noted in all; seven had heterologous elements (six with fetal-type cartilage) and eight displayed focal anaplasia. The remaining five neoplasms showed only a minor component (≤20%) of classic morphology, with anaplasia noted in four and tumor cell necrosis in three. The most frequent mutations detected were in DICER1 (14/21), TP53 (7/20), PI3K/AKT/mTOR pathway (7/20), and KRAS/NRAS (5/20). Copy-number alterations were present in 10/19 tumors. Overall, 8/14 DICER1-associated ucERMS showed concurrent loss of function and hotspot mutations in DICER1, which is a feature more likely to be seen in tumors associated with DICER1 syndrome. Germline data were available for two patients, both DICER1 wild type (one with concurrent loss of function and hotspot alterations). DICER1-associated ucERMS were more likely to show a classic histological appearance including heterologous elements than DICER1-independent tumors. No differences in survival were noted between the two groups, but both patients with extrauterine disease at diagnosis and two with recurrences died from disease. As no patients had a known personal or family history of DICER1 syndrome, we favor most DICER1-associated ucERMS to be sporadic.

Primary Synovial Sarcoma of the Uterine Cervix: First Case Report

Synovial sarcoma is a translocation associated soft tissue malignancy frequently affecting young adults. The classic translocation is t(X;18)(p11.2;q11.2): SS18-SSX1/2/4 fusion. Synovial sarcoma tends to favor the distal extremities but can also arise in other locations. To date, no case of primary synovial sarcoma of the uterine cervix has been reported. We report a 42-yr-old woman with no prior history who presented to clinic with vaginal spotting for 3 mo and was found to have a large mass in the uterine cervix. The mass was evacuated from the vagina and sent for pathologic diagnosis. Sections showed proliferation of monotonous spindle cells with scant eosinophilic cytoplasm, round to slightly irregular nuclei, variable nucleoli and frequent mitosis in a background of delicate capillary and occasional thick-walled vessels. No malignant epithelium was identified in the entire specimen. On immunohistochemical workup tumor cells were negative for pan cytokeratin, OSCAR, EMA, chromogranin, S100, SMA, desmin, myogenin, WT1, CD117, CD34, and BRG1. CD45 was positive in a few inflammatory cells. Cyclin D1 showed partial weak to moderate nuclear reactivity. CD99 demonstrated strong diffuse membranous reactivity and BCL-2 showed strong cytoplasmic staining in 60% of tumor cells. Florescence in situ hybridization results for EWSR1, BCOR, and CIC gene rearrangements were negative, however, florescence in situ hybridization results for SS18 (SYT) (18q11) gene rearrangement was positive. A diagnosis of monophasic synovial sarcoma was rendered. We review the differential diagnoses of tumors with similar morphology and discuss the diagnostic process. With this case report it is imperative to include synovial sarcoma in differential diagnosis list of sarcomas of uterus and cervix.

LG-ESSs and HG-ESSs: underlying molecular alterations and potential therapeutic strategies

Endometrial stromal tumors (ESTs) include endometrial stromal nodule (ESN), low-grade endometrial stromal sarcoma (LG-ESS), high-grade endometrial stromal sarcoma (HG-ESS), and undifferentiated uterine sarcoma (UUS). Since these are rare tumor types, there is an unmet clinical need for the systematic therapy of advanced LG-ESS or HG-ESS. Cytogenetic and molecular advances in ESTs have shown that multiple recurrent gene fusions are present in a large proportion of LG-ESSs, and HG-ESSs are identified by the tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein epsilon (YWHAE)-family with sequence similarity 22 (FAM22) fusion. Recently, a group of ESSs harboring both zinc finger CCCH domain-containing protein 7B (ZC3H7B)-B-cell lymphoma 6 corepressor(BCOR) fusion and internal tandem duplication (ITD) of the BCOR gene have been provisionally classified as HG-ESSs. In this review, we firstly describe current knowledge about the molecular characteristics of recurrent aberrant proteins and their roles in the tumorigenesis of LG-ESSs and HG-ESSs. Next, we summarize the possibly shared signal pathways in the tumorigenesis of LG-ESSs and HG-ESSs, and list potentially actionable targets. Finally, based on the above discussion, we propose a few promising therapeutic strategies for LG-ESSs and HG-ESSs with recurrent gene alterations.

A Case Series of BCOR Sarcomas With a New Splice Variant of BCOR/CCNB3 Fusion Gene

BACKGROUND/AIM

Undifferentiated round cell sarcomas are a heterogeneous group of sarcomas. Identification of BCOR alterations, such as BCOR/CCNB3 and BCOR/MAML3 fusion genes and BCOR ITD has recently contributed in the precise diagnosis of these neoplasms, defining a new entity of the current classification of soft tissue and bone sarcomas. BCOR sarcomas share both morphological and genetic characteristics distinct from Ewing sarcomas. The scope of our study was to retrospectively identify BCOR sarcomas and find the correlations with the clinical outcome of these patients.

PATIENTS AND METHODS

Histopathology and immunohistochemistry of pediatric tumor samples were combined with molecular testing (PCR) and fluorescent in situ hybridization to find BCOR sarcomas.

RESULTS

We, herein, present our experience with BCOR sarcomas in a referral center of Greece. Moreover, we report in one case the detection of a variant BCOR/CCNB3 fusion not previously described.

CONCLUSION

We are the first to report a splice variant of BCOR/CCNB3 which reveals the central position of BCOR in the oncogenesis of these tumors, furthermore we highlight the importance of molecular diagnostics in Ewing-like sarcomas and discuss the current treatment options for this rare entity.

Genomic alterations in gynecological malignancies: histotype-associated driver mutations, molecular subtyping schemes, and tumorigenic mechanisms

There are numerous histological subtypes (histotypes) of gynecological malignancies, with each histotype considered to largely reflect a feature of the "cell of origin," and to be tightly linked with the clinical behavior and biological phenotype of the tumor. The recent advances in massive parallel sequencing technologies have provided a more complete picture of the range of the genomic alterations that can persist within individual tumors, and have highlighted the types and frequencies of driver-gene mutations and molecular subtypes often associated with these histotypes. Several large-scale genomic cohorts, including the Cancer Genome Atlas (TCGA), have been used to characterize the genomic features of a range of gynecological malignancies, including high-grade serous ovarian carcinoma, uterine corpus endometrial carcinoma, uterine cervical carcinoma, and uterine carcinosarcoma. These datasets have also been pivotal in identifying clinically relevant molecular targets and biomarkers, and in the construction of molecular subtyping schemes. In addition, the recent widespread use of clinical sequencing for the more ubiquitous types of gynecological cancer has manifested in a series of large genomic datasets that have allowed the characterization of the genomes, driver mutations, and histotypes of even rare cancer types, with sufficient statistical power. Here, we review the field of gynecological cancer, and seek to describe the genomic features by histotype. We also will demonstrate how these are linked with clinicopathological attributes and highlight the potential tumorigenic mechanisms.

Low-grade Endometrial Stromal Sarcoma With Sex Cord-like Differentiation and PHF1-JAZF1 Fusion With Deletions: A Diagnostic Pitfall of JAZF1 FISH

The molecular knowledge on endometrial stromal neoplasms has been rapidly increasing and is considered complementary to morphologic and immunohistochemical findings for better categorization of these tumors. The most common molecular alteration observed in low-grade endometrial stromal sarcomas is the JAZF1-SUZ12 fusion, whereas, low-grade endometrial stromal sarcoma with sex cord-like differentiation have been shown more commonly to have fusions involving PHF1. Herein, we present a low-grade endometrial stromal sarcoma with sex cord-like differentiation with a fluorescence in situ hybridization showing the apparent loss of one copy of JAZF1 5' and 3' signals, rather than the expected "break-apart" pattern seen in the setting of a JAZF1 fusion. The case was then further evaluated by chromosome microarray and RNA fusion analysis. Overall, the molecular findings supported a PHF1-JAZF1 fusion with deletions right before and after the JAZF1 locus, impairing probe binding and resulting in the unusual "deletion" pattern observed in the JAZF1 fluorescence in situ hybridization, which would not intuitively suggest a fusion involving JAZF1. This case illustrates the importance of integration of morphological and molecular findings as well as the limitations of fluorescence in situ hybridization in detecting fusions, particularly in the setting of more complex chromosomal alterations even though the fusion partners are well-known.

Targeted RNA expression profiling identifies high-grade endometrial stromal sarcoma as a clinically relevant molecular subtype of uterine sarcoma

High-grade endometrial stromal sarcoma (HGESS) may harbor YWHAE-NUTM2A/B fusion, ZC3H7B-BCOR fusion, and BCOR internal tandem duplication (ITD). NTRK3 upregulation and pan-Trk expression were reported in soft tissue lesions that share similar morphology and genetic abnormalities. To confirm these findings in HGESS, differential expression analysis was performed at gene level comparing 11 HGESS with 48 other uterine sarcomas, including 9 low-grade endometrial stromal sarcomas, 23 undifferentiated uterine sarcomas, and 16 leiomyosarcomas, using targeted RNA sequencing data. Pan-Trk immunohistochemistry was performed on 35 HGESS, including 10 tumors with RNA expression data, with genotypes previously confirmed by targeted RNA sequencing, fluorescence in situ hybridization, and/or genomic PCR. Unsupervised hierarchical clustering of the top 25% of differentially expressed probes identified three molecular groups: (1) high NTRK3, FGFR3, RET, BCOR, GLI1, and PTCH1 and low ESR1 expression; (2) low NTRK3, FGFR3, RET, BCOR, GLI1, and PTCH1 and high ESR1 expression; and (3) low NTRK3, FGFR3, RET, BCOR, GLI1, PTCH1, and ESR1 expression. Among HGESS, 64% of tumors clustered in group 1, while 27% clustered in group 2. Cytoplasmic and/or nuclear pan-Trk staining of variable extent and intensity was seen in 91% of HGESS regardless of cyclin D1 and/or BCOR positivity. ER and PR expression was seen in 44% of HGESS despite ESR1 downregulation. Two patients with ER and PR positive but ESR1 downregulated stage I HGESS were treated with endocrine therapy, and both recurred at 12 and 36 months after primary resection. By RNA expression, HGESS appear homogenous and distinct from other uterine sarcomas by activation of kinases, including NTRK3, and sonic hedgehog pathway genes along with downregulation of ESR1. Most HGESS demonstrate pan-Trk staining which may serve as a diagnostic biomarker. ESR1 downregulation is seen in some HGESS that express ER and PR which raises implications in the utility of endocrine therapy in these patients.

Update on Endometrial Stromal Tumours of the Uterus

Endometrial stromal tumours (ESTs) are rare, intriguing uterine mesenchymal neoplasms with variegated histopathological, immunohistochemical and molecular characteristics. Morphologically, ESTs resemble endometrial stromal cells in the proliferative phase of the menstrual cycle. In 1966 Norris and Taylor classified ESTs into benign and malignant categories according to the mitotic count. In the most recent classification by the WHO (2020), ESTs have been divided into four categories: Endometrial Stromal Nodules (ESNs), Low-Grade Endometrial Stromal Sarcomas (LG-ESSs), High-Grade Endometrial Stromal Sarcomas (HG-ESSs) and Undifferentiated Uterine Sarcomas (UUSs). ESNs are clinically benign. LG-ESSs are tumours of low malignant potential, often with indolent clinical behaviour, with some cases presented with a late recurrence after hysterectomy. HG-ESSs are tumours of high malignant potential with more aggressive clinical outcome. UUSs show high-grade morphological features with very aggressive clinical behavior. With the advent of molecular techniques, the morphological classification of ESTs can be integrated with molecular findings in enhanced classification of these tumours. In the future, the morphological and immunohistochemical features correlated with molecular categorisation of ESTs, will become a robust means to plan therapeutic decisions, especially in recurrences and metastatic disease. In this review, we summarise the morphological, immunohistochemical and molecular features of ESTs with particular reference to the most recent molecular findings.

Specific and Sensitive Diagnosis of BCOR-ITD in Various Cancers by Digital PCR

BCOR is an epigenetic regulator altered by various mechanisms including BCOR-internal tandem duplication (BCOR-ITD) in a wide range of cancers. Six different BCOR-ITD in the 3’-part of the coding sequence of exon 15 have been reported ranging from 89 to 114 bp in length. BCOR-ITD is a common genetic alteration found in clear cell sarcoma of the kidney and primitive myxoid mesenchymal tumor of infancy (PMMTI) and it characterizes a new type of central nervous system tumor: “CNS tumor with BCOR-ITD”. It can also be detected in undifferentiated round cell sarcoma (URCS) and in high-grade endometrial stromal sarcoma (HGESS). Therefore, it is of utmost importance to search for this genetic alteration in these cancers with the most frequent technique being RNA-sequencing. Here, we developed a new droplet PCR assay (dPCR) to detect the six sequences characterizing BCOR-ITD. To achieve this goal, we used a single colored probe to detect both the duplicated region and the normal sequence that acts as a reference. We first generated seven synthetic DNA sequences: ITD0 (the normal sequence) and ITD1 to ITD6 (the duplicated sequences described in the literature) and then we set up the optima dPCR conditions. We validated our assay on 19 samples from a representative panel of human tumors (9 HGNET-BCOR, 5 URCS, 3 HGESS, and 2 PMMTI) in which BCOR-ITD status was known using at least one other method including RNA sequencing, RT-PCR or DNA-methylation profiling for CNS tumors. Our results showed that our technique was 100% sensitive and specific. DPCR detected BCOR-ITD in 13/19 of the cases; in the remaining 6 cases additional RNA-sequencing revealed BCOR gene fusions. To conclude, in the era of histomolecular classification of human tumors, our modified dPCR assay is of particular interest to detect BCOR-ITD since it is a robust and less expensive test that can be applied to a broad spectrum of cancers that share this alteration.

[Interdisciplinary S2k guidelines on the diagnosis and treatment of uterine sarcomas-recommendations for surgical pathology]

Uterine sarcomas represent a heterogeneous group of rare malignancies, derived from the myometrium, the endometrial stroma, and very rarely from the nonspecialized uterine soft tissue. The actual incidence is about 1.5 for Caucasian and 3.0 for Afro-American women. There is no grading system for leimoysarcoma defined by the WHO classification; however, if clinicians request, the FNCLCC grading can be specified in analogy to soft tissue sarcomas. Adenosarcomas must be distinguished from adenofibromas (the existence of which is questionable)-with the vast majority of these tumors being uterine adenosarcomas. Within adenosarcomas, deep myometrial invasion (>50%), sarcomatous overgrowth, and a high-grade heterologous component are associated with a higher recurrence rate and poor survival. The immunohistochemical panel represents a very helpful tool for distinguishing low-grade from high grade endometrial stromal sarcomas (ESS) and may be supplemented by molecular analyses. Steroid hormone receptor analysis should be performed for all ESS due to the possible therapeutic relevance. Undifferentiated uterine sarcomas represent a diagnosis of exclusion and have a very poor prognosis. Carcinosarcomas represent a special subtype of endometrial carcinomas and are in fact not uterine sarcomas. Uterine sarcomas may present substantial intratumoral heterogeneity and adequate embedding is mandatory. Lesions ≤2 cm in the largest dimension should be processed completely and larger tumors should be processed with one block per centimeter for the largest tumor dimension.

Recent advances in smooth muscle tumors with PGR and PLAG1 gene fusions and myofibroblastic uterine neoplasms

Uterine epithelioid and myxoid leiomyosarcomas and inflammatory myofibroblastic tumors are rare mesenchymal neoplasms. Next-generation sequencing recently detected novel PGR fusions in uterine epithelioid leiomyosarcomas that demonstrate characteristic rhabdoid and spindled morphology. PLAG1 gene fusions have also been identified in a subset of myxoid leiomyosarcomas and are associated with PLAG1 overexpression. ALK rearrangements underpin the vast majority of uterine inflammatory myofibroblastic tumors, which demonstrate morphologic, and immunohistochemical features similar to those of inflammatory myofibroblastic tumors elsewhere. This review summarizes the morphologic, immunophenotypic, and molecular genetic features of PGR fusion-positive epithelioid leiomyosarcoma, PLAG1 fusion-positive myxoid leiomyosarcoma, and inflammatory myofibroblastic tumors of the uterus.

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.

NTRK and other recently described kinase fusion positive uterine sarcomas: A review of a group of rare neoplasms

The landscape of uterine sarcomas has greatly expanded in recent years to include neoplasms with recurrent gene fusions, such as BCOR and YWHAE translocated high-grade endometrial stromal sarcomas. Sophisticated molecular techniques have also resulted in the description of "new" entities associated with recurrent kinase fusions involving NTRK and RET as well as COL1A1-PDGFB rearranged uterine sarcomas. These rare neoplasms will be discussed in this review, highlighting that some of the underlying molecular events are clinically actionable and potentially susceptible to targeted therapy. While relatively few of these neoplasms have been described to date, likely being previously lumped under the spectrum of undifferentiated uterine sarcoma, the number of cases will expand in the future given their recognition and the increasing availability of molecular testing. These neoplasms have overlapping morphology (often with a "fibrosarcoma-like" appearance) and immunohistochemical features, and are characterized by variable clinical outcomes. Although immunohistochemistry may assist in some cases, a definitive subclassification requires confirmatory molecular studies. As these molecular assays may not be routinely available in most laboratories, referral to reference centers may be needed. In order to assist the pathologist, we suggest a diagnostic algorithm for routine practice when dealing with a malignant or potentially malignant uterine spindle cell neoplasm.

Molecular pathogenesis and prognostication of "low-grade'' and "high-grade" endometrial stromal sarcoma

Endometrial stromal sarcomas (ESS) are a heterogeneous group of rare mesenchymal cancers. Considerable knowledge has been gained in recent years about the molecular characteristics of these cancers, which helps to classify them in a more meaningful manner leading to improved diagnosis, prognostication, and treatment. According to this classification, ESS is now grouped as low‐ or high‐grade. ESS may have overlapping clinical presentation, morphology, and immunohistochemical profile. Their genetic characteristics allow subdivision of many of them depending on which pathogenetically important fusion genes they carry, but clearly much more needs to be unraveled in this regard. We here provide an overview of the molecular pathogenetic knowledge gained so far on low‐ and high‐grade ESS.