Infrequent SMARCB1/INI1 gene alteration in epithelioid sarcoma: a useful tool in distinguishing epithelioid sarcoma from malignant rhabdoid tumor

Expression of Forkhead Box M1 and Anticancer Effects of FOXM1 Inhibition in Epithelioid Sarcoma

Epithelioid sarcoma (ES) is a rare aggressive sarcoma that, unlike most soft-tissue sarcomas, shows a tendency toward local recurrence and lymph node metastasis. Novel antitumor agents are needed for ES patients. Forkhead box transcription factor 1 (FOXM1) is a member of the Forkhead transcription factor family and is associated with multiple oncogenic functions; FOXM1 is known to be overexpressed and correlated with pathogenesis in various malignancies. In this study, we immunohistochemically analyzed FOXM1 expression levels and their clinical, clinicopathologic, and prognostic significance in 38 ES specimens. In addition, to investigate potential correlations between FOXM1 downregulation and oncologic characteristics, we treated ES cell lines with thiostrepton, a naturally occurring antibiotic that inhibits both small interfering RNA (siRNA) and FOXM1. In the analyses using ES samples, all 38 specimens were diagnosed as positive for FOXM1 by immunohistochemistry. We separated specimens into high (n = 19) and low (n = 19) FOXM1-protein expression groups by staining index score, and into large (n = 12), small (n = 25), and unknown (n = 1) tumor-size groups using a cutoff of 5 cm maximum diameter. Although there were significantly more samples with high FOXM1 expression in the large tumor group (P = .013), there were no significant differences with respect to age (P = 1.00), sex (P = .51), primary site of origin (P = .74), histologic subtypes (P = 1.00), depth (P = .74), or survival rate (P = .288) between the high and low FOXM1-protein expression groups. In the in vitro experiments using ES cell lines, FOXM1 siRNA and thiostrepton successfully downregulated FOXM1 mRNA and protein expression. Furthermore, downregulation of FOXM1 inhibited cell proliferation, drug resistance against chemotherapeutic agents, migration, and invasion and caused cell cycle arrest in the ES cell lines. Finally, cDNA microarray analysis data showed that FOXM1 regulated cIAP2, which is one of the apoptosis inhibitors activated by the TNFα-mediated NF-κB pathway. In conclusion, the FOXM1 gene may be a promising therapeutic target for ES.

Epigenetic determinants in soft tissue sarcomas: molecular mechanisms and therapeutic targets

INTRODUCTION

Soft tissue sarcomas are a group of rare, mesenchymal tumors characterized by dismal prognosis in advanced/metastatic stages. Knowledge of their molecular determinants is still rather limited. However, in recent years, epigenetic regulation - the modification of gene expression/function without DNA sequence variation - has emerged as a key player both in sarcomagenesis and sarcoma progression.

AREAS COVERED

Herein, we describe and review the main epigenetic mechanisms involved in chromatin remodeling and their role as disease drivers in different soft tissue sarcoma histotypes, focusing on epithelioid sarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumors. Focusing on chromatin-remodeling complexes, we provide an in-depth on the role of BAF complex alterations in these soft tissue sarcoma histotypes. In parallel, we highlight current state-of-the-art and future perspectives in the development of rational, innovative treatments leveraging on epigenetic dysregulation in soft tissue sarcomas.

EXPERT OPINION

Therapeutic options for metastatic/advanced sarcomas are to date very limited and largely represented by cytotoxic agents, with only modest results. In the continuous attempt to find novel targets and innovative, effective drugs, epigenetic mechanisms represent an emerging and promising field of research, especially for malignant peripheral nerve sheath tumors, epithelioid and synovial sarcoma.

Targeting EZH2 in SMARCB1-deficient sarcomas: Advances and opportunities to potentiate the efficacy of EZH2 inhibitors

Soft tissue sarcomas (STSs) are rare mesechymal malignancies characterized by distintive molecular, histological and clinical features. Many STSs are considered as predominatly epigenetic diseases due to underlying chromatin deregulation. Discovery of deregulated functional antagonism between the chromatin remodeling BRG1/BRM-associated (BAFs) and the histone modifying Polycomb repressor complexes (PRCs) has provided novel actionable targets. In epithelioid sarcoma (ES), extracranial, extrarenal malignant rhabdoid tumors (eMRTs) and synovial sarcoma (SS), the total or partial loss of the BAF core subunit SMARCB1, driven by different alterations, is associated with PRC2 deregulation and dependency on its enzymatic subunit, EZH2. In these SMARCB1-deficient STSs, aberrant EZH2 expression and/or activity emerged as a druggable vulnerability. Although preclinical investigation supported EZH2 targeting as a promising therapeutic option, clinical studies demonstrated a variable response to EZH2 inhibitors. Actually, whereas the clinical benefit recorded in ES patients prompted the FDA approval of the EZH2 inhibitor tazemetostat, the modest and sporadic responses observed in eMRT and SS patients highlighted the need to deepen mechanistic as well as pharmacological investigations to improve drug effectiveness. We summarize the current knowledge of different mechanisms driving SMARCB1 deficiency and EZH2 deregulation in ES, eMRT and SS along with preclinical and clinical studies of EZH2-targeting agents. Possible implication of the PRC2- and enzymatic-independent functions of EZH2 and of its homolog, EZH1, in the response to anti-EZH2 agents will be discussed together with combinatorial strategies under investigation to improve the efficacy of EZH2 targeting in these tumors.

Malignant rhabdoid tumor of the omentum in an adult male: a case report and literature review

Malignant rhabdoid tumors (MRTs) are rare tumors with high mortality rates and poor prognoses. MRTs occur mainly in the central nervous system, kidneys, and soft tissues, but rarely in the omentum. MRTs occur more commonly in infants and children and less frequently in adults. Here, we report the first observed case of MRT in an adult omentum. A 35-year-old man with abdominal distension and pain was admitted to the emergency department. Previously, several hospitals considered patients with cirrhosis who had not received active treatment. Computed tomography and magnetic resonance imaging revealed diffuse omental thickening and massive ascites. The surgery was performed at our hospital, and the pathological diagnosis was MRT with a SMARCB1(INI-1) deletion. Postoperatively, his symptoms improved, and he underwent five cycles of chemotherapy. However, 6 months after surgery, the tumor developed liver metastases, and the patient subsequently died. Primary MRT of the greater omentum is rare, and its pathological diagnosis usually requires extensive clinicopathological evaluation of various differential diagnoses and an appropriate work-up to exclude other malignancies associated with SMARCB1 deletion. At the same time, the lack of specific signs of omental MRT and its rapid progression should alert clinicians.

The Recent Advances in Molecular Diagnosis of Soft Tissue Tumors

Soft tissue tumors are rare mesenchymal tumors with divergent differentiation. The diagnosis of soft tissue tumors is challenging for pathologists owing to the diversity of tumor types and histological overlap among the tumor entities. Present-day understanding of the molecular pathogenesis of soft tissue tumors has rapidly increased with the development of molecular genetic techniques (e.g., next-generation sequencing). Additionally, immunohistochemical markers that serve as surrogate markers for recurrent translocations in soft tissue tumors have been developed. This review aims to provide an update on recently described molecular findings and relevant novel immunohistochemical markers in selected soft tissue tumors.

Genetic and environmental reprogramming of the sarcoma epigenome

Sarcomas are rare and heterogenous mesenchymal tumors occurring in soft tissue and bone. The World Health Organization Classification of sarcomas comprises more than hundred different entities which are very diverse in their molecular, genetic and epigenetic signatures as they are in their clinical presentations and behaviors. While sarcomas can be associated with an underlying hereditary cancer predisposition, most sarcomas developed sporadically without identifiable cause. Sarcoma oncogenesis involves complex interactions between genetic, epigenetic and environmental factors which are intimately related and intensively studied. Several molecular discoveries have been made over the last decades leading to the development of new therapeutic avenues. Sarcoma research continues its effort toward a more specific and personalized approach to all sarcoma sub-types to improve patient outcomes and this through world-wide collaboration. This chapter on "Genetic and Environmental Reprogramming of the Sarcoma Epigenome" provides a comprehensive review of general concepts and epidemiology of sarcoma as well as a detailed description of the genetic, molecular and epigenetic alterations seen in sarcomas, their therapeutic implications and ongoing research. This review also presents evidenced-based data on the environmental and occupational factors possibly involved in the etiology of sarcomas and a brief discussion on the role of the microbiome in sarcoma.

Immunotherapy for SMARCB1-Deficient Sarcomas: Current Evidence and Future Developments

Mutations in subunits of the SWItch Sucrose Non-Fermentable (SWI/SNF) complex occur in 20% of all human tumors. Among these, the core subunit SMARCB1 is the most frequently mutated, and SMARCB1 loss represents a founder driver event in several malignancies, such as malignant rhabdoid tumors (MRT), epithelioid sarcoma, poorly differentiated chordoma, and renal medullary carcinoma (RMC). Intriguingly, SMARCB1-deficient pediatric MRT and RMC have recently been reported to be immunogenic, despite their very simple genome and low tumor mutational burden. Responses to immune checkpoint inhibitors have further been reported in some SMARCB1-deficient diseases. Here, we will review the preclinical data and clinical data that suggest that immunotherapy, including immune checkpoint inhibitors, may represent a promising therapeutic strategy for SMARCB1-defective tumors. We notably discuss the heterogeneity that exists among the spectrum of malignancies driven by SMARCB1-loss, and highlight challenges that are at stake for developing a personalized immunotherapy for these tumors, notably using molecular profiling of the tumor and of its microenvironment.

Poorly differentiated chordoma showing loss of SMARCB1/INI1: Clinicopathological and radiological spectrum of nine cases, including uncommon features of a relatively under-recognized entity

Poorly differentiated chordoma is a newly recognized entity in the recent World Health Organization (WHO) classification of tumors of soft tissue and bone. Slightly over 60 such cases have been documented. Herein, we present a clinicopathological profile, including radiological features, of nine cases, which occurred in five males and four females, with age varying from 1 to 29 years (median = 43), in the cervical spine (n = 2), skull base (n = 2), clivus (n = 2), thoracic spine (n = 1) lumbar spine (n = 1) and coccyx (n = 1) Average tumor size was 4.8 cm. None of the 6-referral cases was diagnosed as a poorly differentiated chordoma at the referring laboratory. Histopathologically, all cases displayed a cellular tumor comprising polygonal cells (n = 9) displaying moderate to marked nuclear pleomorphism with prominent nucleoli (n = 7), eosinophilic (n = 9) to vacuolated cytoplasm (n = 7), rhabdoid morphology (n = 4), interspersed mitotic figures (n = 5), focal necrosis (n = 6) and inflammatory cells (n = 9). A single tumor displayed areas resembling classic chordoma, transitioning into poorly differentiated areas. There were multinucleate giant cells and physaliphorous cells in two tumors, each, respectively. Immunohistochemically, tumor cells were positive for AE1/AE3 (7/7), EMA (7/7), cytokeratin (CK) MNF116 (1/1), OSCAR (1/1), brachyury (9/9, diffusely), S100P (4/7, mostly focally), and glypican 3(2/4). SMARCB1/INI1 was completely lost in all nine tumors. A single case tested by FISH showed homozygous deletion of the SMARCB1 gene. Therapeutically (n = 7), all patients were treated with surgical resection (invariably incomplete) (n = 5), followed by adjuvant radiation therapy (n = 4) and chemotherapy (n = 4). While a single patient partially responded to treatment and another patient is alive with no evidence of disease after 23 years, three patients died of disease, six, eight, and 11 months post-diagnosis, despite adjuvant treatments. A single patient presented with a metastatic lung nodule, while another developed widespread metastasis. Poorly differentiated chordomas display a spectrum of features, are associated with a lower index of suspicion for a diagnosis, and display aggressive outcomes. Critical analysis of radiological and histopathological features, including necessary immunostains (brachyury and SMARCB1/INI1), is necessary for their timely diagnosis. These tumors show loss of SMARCB1/INI1 immunostaining and homozygous deletion of INI1/SMARCB1 gene.

Myxoepithelioid tumour with chordoid features: a clinicopathological, immunohistochemical and genetic study of 14 cases of SMARCB1/INI1-deficient soft-tissue neoplasm

AIMS

Complete loss of SMARCB1/INI1 in soft-tissue tumours such as malignant rhabdoid tumour, epithelioid sarcoma, myoepithelial tumour of soft tissue and extraskeletal myxoid chondrosarcoma is often associated with high-grade malignancy and poor prognosis. The diagnosis is sometimes challenging, owing to histological similarities, so careful differential diagnosis is required. Therefore, soft-tissue tumours with complete SMARCB1/INI1 loss could potentially include an unknown entity.

METHODS AND RESULTS

We analysed 160 cases of SMARCB1/INI1-deficient soft-tissue tumour, and found 14 cases that were not classifiable into already existing categories and had common clinical and histological features. These involved two male and 12 female patients, ranging in age from 20 years to 61 years. The tumours were located in the the puboinguinal region (n = 13) and pelvic cavity (n = 1). Histologically, the tumours showed relatively uniform epithelioid to spindle-shaped cells with myxoid stroma. All tumours showed immunoreactivity for brachyury, epithelial membrane antigen, and progesterone receptor, and 12 of 14 cases did so for oestrogen receptor. Variable positive staining for α-smooth muscle actin, S100 and glial fibrillary acidic protein (GFAP) was seen. NR4A3 and EWSR1 gene rearrangements were not detected in 13 and 11 examined cases, respectively. Clinical follow-up data for the 14 patients showed that 13 were alive without disease and one had been lost to follow-up; four patients developed local recurrence and/or metastases.

CONCLUSION

The designation 'myxoepithelioid tumour with choroid features' (METC) was proposed as a tumour with intermediate malignancy controllable with appropriate treatment, including the entity of myoepithelioma-like tumour of the vulvar region. METC represents a novel and independent subset that is histologically, biologically and clinically distinct from already existing SMARCB1/INI1-deficient soft-tissue tumours.

Update on SWI/SNF-related gynecologic mesenchymal neoplasms: SMARCA4-deficient uterine sarcoma and SMARCB1-deficient vulvar neoplasms

Our knowledge regarding the role of genes encoding the chromatin remodeling switch/sucrose non-fermenting (SWI/SNF) complex in the initiation and progression of gynecologic malignancies continues to evolve. This review focuses on gynecologic tumors in which the sole or primary genetic alteration is in SMARCA4 or SMARCB1, two members of the SWI/SNF chromatin remodeling complex. In this review, we present a brief overview of the classical example of such tumors, ovarian small cell carcinoma of hypercalcemic type, and then a detailed review and update of SMARCB1-deficient and SMARCA4-deficient tumors of the uterus and vulva.

A case of primary distal-type epithelioid sarcoma of the lumbar vertebra with a review of literature

Epithelioid sarcoma (EpS) is a rare malignant neoplasm that accounts for < 1% of adult soft tissue sarcomas. Primary EpS of the bone is extremely rare and only a few cases have been reported to date. We report a case of primary distal-type EpS of the lumbar vertebra. A 30-year-old man without any history of malignant tumors had complained of lumbago for 3 months before visiting the hospital. Magnetic resonance imaging (MRI) of the lumbar spine showed a high signal intensity on the fat-suppressed T2-weighted image (WI) and a low signal on the T1WI at the L1 vertebral body. The tumor protruded toward the anterior components. Systemic radiological examination revealed no other lesion. A biopsy revealed a primary malignant tumor with epithelioid features. After chemotherapy, total en bloc spondylectomy was performed. Macroscopically, the tumor replaced the entire L1 with necrosis. Histologically, the tumor showed nodules of epithelioid cells that were strongly positive for epithelial markers, but a lack of INI1 expression. Central necrosis in the tumor nodule was also observed. This tumor showed loss of heterozygosity at the SMARCB1 locus but without the SMARCB1 mutation. The result of Foundation One ®CDx showed no actionable mutations. Seven months after surgery, a subcutaneous metastasis to the left cheek and bilateral lung metastasis with pleural dissemination were observed on radiological examination. A final diagnosis of distal-type EpS was made based on these findings. The patient died of the disease 8 months after surgery.

Epithelioid Sarcoma-From Genetics to Clinical Practice

Epithelioid sarcoma is a mesenchymal soft tissue sarcoma often arising in the extremities, usually in young adults with a pick of incidence at 35 years of age. Epithelioid sarcoma (ES) is characterized by the loss of SMARCB1/INI1 (integrase interactor 1) or other proteins of the SWI/SNF complex. Two distinct types, proximal and distal, with varying biology and treatment outcomes, are distinguished. ES is known for aggressive behavior, including a high recurrence rate and regional lymph node metastases. An optimal long-term management strategy is still to be defined. The best treatment of localized ES is wide surgical resection. Neo-adjuvant or adjuvant radiotherapy may be recommended, as it reduces the local recurrence rate. Sentinel lymph node biopsy should be considered in ES patients. Patients with metastatic ES have a poor prognosis with an expected median overall survival of about a year. Doxorubicin-based regimens are recommended for advanced ES. Tazemetostat, an EZH2 methyltransferase, has shown promising results in ES patients. Novel therapies, including immunotherapy, are still needed.

Loss of SMARCB1/INI1 Immunoexpression in Chordoid Meningiomas

Background

Chordoid meningiomas have an aggressive clinical course characterized by frequent recurrences. Recent whole-genome sequencing studies demonstrated Chr22 loss in chordoid meningiomas not accounted for by NF2 mutations. SMARCB1/INI1 is a candidate gene on Chr22, which has not been analyzed extensively in meningiomas. AKT1 mutation has been recently identified to be a driver of meningiomagenesis.

Materials and Methods

Cases of chordoid meningioma were retrieved along with meningiomas of other subtypes for comparison. INI1 immunohistochemistry was performed. SMARCB1 and AKT1 were analyzed by sequencing.

Results

Sixteen chordoid meningiomas were identified (1.1% of all meningiomas). Six cases (37.5%) showed loss of INI1 immunoexpression. All other meningioma subtypes (n = 16) retained INI1 immunoexpression. AKT1 E17K mutation was identified in one case (16.7%). Notably, SMARCB1 mutations were not identified in any of the chordoid meningiomas analyzed, including those showing INI1 loss immunohistochemically.

Conclusion

This is the first study to demonstrate loss of SMARCB1/INI1 immunoexpression in chordoid meningiomas, adding to the tumors with INI1 loss. However, in absence of INI1 mutation, mechanisms for INI1 loss require further evaluation. Identification of AKT1 mutation opens up new avenues for targeted therapy in patients with such aggressive tumors.

Soft Tissue Special Issue: Skeletal Muscle Tumors: A Clinicopathological Review

Skeletal muscle tumors are classified into rhabdomyoma and embryonal, alveolar, spindle cell/sclerosing and pleomorphic rhabdomyosarcoma according to WHO classifications of tumors. These tumors arise mostly in the head and neck and, in childhood, represent the largest subset of soft tissue tumors. Although these skeletal muscle tumors show common immunoexpression of two myogenic regulatory factors, MyoD1 and myogenin, their molecular biological backgrounds are quite different. Therefore, treatment regimens vary a great deal depending on the histological subtype. Histopathologically, rhabdomyoma is characterized by well-demarcated lesions with no invasion of the surrounding tissue. Embryonal rhabdomyosarcoma is composed of primitive mesenchymal cells in various stages of myogenesis and shows heterogeneous nuclear staining for myogenin. Alveolar rhabdomyosarcoma, on the other hand, shows a proliferation of uniform primitive round cells arranged in alveolar patterns. The tumor cells at the periphery of alveolar structures adhere in a single layer to the fibrous septa. Diffuse and strong nuclear immunoexpression for myogenin is observed. In genetic backgrounds, almost all alveolar rhabdomyosarcomas contain a characteristic fusion gene such as PAX3/7-FOXO1. Spindle cell/sclerosing rhabdomyosarcoma is characterized by fascicularly arranged spindle-shaped cells or dense hyalinized collagenous matrix. NCOR2- or VGLL2-related gene fusions or MYOD1 (p.L122R) mutation is commonly recognized. Epithelioid rhabdomyosarcoma is a rare variant of rhabdomyosarcoma that shows a proliferation of epithelioid tumor cells having large vesicular nuclei, prominent nucleoli, and amphophilic to eosinophilic cytoplasm arranged in sheets. As these characteristic histological and molecular features are present in each subtype, it is possible to diagnose skeletal muscle tumors accurately.

Proximal-type epithelioid sarcoma of the oral cavity: a case report and literature review

Proximal-type epithelioid sarcoma (PES) is an exceedingly rare malignant tumor of soft tissue; PES within the oral cavity is even rarer. Pathologic examination is the primary diagnostic modality, and surgical treatment is recommended as the preferred method for the treatment of PES. Currently, there is a paucity of literature that systematically reports on PES in the oral cavity. Here, we describe a 42-year-old man with PES in the oral cavity, which showed positivity for vimentin, cytokeratin, CD31, S-100 but did not express BCL-2, HMB-45, or desmin. We performed a wide excision and neck dissection, and then used the free anterolateral thigh flap to reconstruct the defect in the soft tissue. Furthermore, we review the current literature with regard to diagnosis and treatment of PES.

INI Expressing Epithelioid Sarcoma with Osteoclastic Giant Cells in a Child: A Case Report with Summary of Prior Published Cases

BACKGROUND

Epithelioid sarcoma is a heterogeneous tumor with 2 subtypes, classic and proximal. The proximal variant is more aggressive and occurs in proximal location in young adults.

CASE REPORT

We present a proximal epithelioid sarcoma in the leg of an 8 year old girl with rhabdoid morphology and scattered osteoclastic giant cells. Nuclear INI-1 was retained. Despite wide local excision, local recurrence occurred at 8 months. Following re-excision, she developed a chest wall metastasis after 9 months.

CONCLUSION

Epithelioid sarcoma, proximal type with osteoclastic giant cells in the pediatric age group has not been reported previously and should be considered in the differential diagnoses of tumors with epithelioid cell morphology and scattered osteoclastic giant cells. Retained INI expression helped to differentiate this tumor from malignant rhabdoid tumor.

Oncogenic roles of SMARCB1/INI1 and its deficient tumors

SMARCB1/INI1 is one of the core subunit proteins of the ATP-dependent SWI/SNF chromatin remodeling complex, and is identified as a potent and bona fide tumor suppressor. Interactions have been demonstrated between SMARCB1/INI1 and key proteins in various pathways related to tumor proliferation and progression: the p16-RB pathway, WNT signaling pathway, sonic hedgehog signaling pathway and Polycomb pathway. Initially, no detectable SMARCB1/INI1 protein expression was found in malignant rhabdoid tumor cells, whereas all other kinds of tumor cells and non-tumorous tissue showed SMARCB1/INI1 protein expression. Therefore, immunohistochemical testing for the SMARCB1/INI1 antibody has been considered useful in confirming the histologic diagnosis of malignant rhabdoid tumors. However, recently, aberrant expression of SMARCB1/INI1 has been found in various tumors such as epithelioid sarcomas, schwannomatosis, synovial sarcomas, and so on. In addition, it has been reported that aberrant expression can be classified into three patterns: complete loss, mosaic expression and reduced expression. Although the various pathways related to mechanisms of tumorigenesis and tumor proliferation are complexly intertwined, the clarification of these mechanisms may contribute to therapeutic strategies in SMARCB1/INI1-deficient tumors. In terms of pathological classifications, SMARCB1/INI1-deficient tumors may be re-classified by genetic backgrounds.

Reclassification of rhabdoid tumor and pediatric undifferentiated/unclassified sarcoma with complete loss of SMARCB1/INI1 protein expression: three subtypes of rhabdoid tumor according to their histological features

Rhabdoid tumor is characterized by rhabdoid cells and shows complete loss of SMARCB1/INI1 protein expression. In existing classifications, the diagnostic synonyms vary depending on the anatomic site: rhabdoid tumors in the central nervous system or extra-central nervous system are, respectively, classified as atypical teratoid/rhabdoid tumor or malignant rhabdoid tumor. In this study, we analyzed the histological, immunohistochemical, microRNA, and clinicopathological statuses of tumors initially diagnosed as malignant rhabdoid tumor (n=33), atypical teratoid/rhabdoid tumor (n=11), and pediatric undifferentiated/unclassified sarcoma (n=8) with complete loss of SMARCB1/INI1 expression, and considered the possibility of their histological reclassification. Our analysis indicated that the tumors could be histologically reclassified into three groups: conventional-type tumors resembling malignant rhabdoid tumor, atypical teratoid/rhabdoid-type tumors resembling atypical teratoid/rhabdoid tumor, and small cell-type tumors resembling malignant lymphoma. The reclassified conventional type was composed of 27 malignant rhabdoid tumors and 9 atypical teratoid/rhabdoid tumors (36 cases). The atypical teratoid/rhabdoid type consisted of six malignant rhabdoid tumors, two atypical teratoid/rhabdoid tumors, and two undifferentiated/unclassified sarcomas (10 cases). The six cases of small cell type were made up of six undifferentiated/unclassified sarcomas. All of the available tumor specimens were positive for vimentin and epithelial marker (EMA, CAM5.2, or AE1/AE3). MicroRNA profiles were not significantly different between the conventional- and small cell-type tumors (Pearson's correlation coefficient: 0.888300 or 0.891388). There was no significant difference in overall survival between atypical teratoid/rhabdoid tumor and malignant rhabdoid tumor (P=0.16). In addition, there were no significant differences in survival between any of the reclassified combinations. In conclusion, we could classify eight tumors initially diagnosed as undifferentiated/unclassified sarcomas into two cases of atypical teratoid/rhabdoid type and six cases of small cell type. We suggest that reclassification of malignant rhabdoid tumors into three groups according to their histologic features rather than the traditional classification by sites of origin would be favorable for their histopathological diagnosis.

Epigenetic regulation of SMARCB1 By miR-206, -381 and -671-5p is evident in a variety of SMARCB1 immunonegative soft tissue sarcomas, while miR-765 appears specific for epithelioid sarcoma. A miRNA study of 223 soft tissue sarcomas

Complete/partial loss of SMARCB1 nuclear-immunopositivity is characteristic of a certain subset of soft tissue sarcomas (STSs). Our previous work showed that oncomiRs-206,-381, and 671-5p could silence the SMARCB1 mRNA and protein expression and that they display significant overexpression in epithelioid sarcomas (ESs). MiR-765 was overexpressed too, but functionally was inactive in the silencing. In the current work, using quantitative PCR, we conducted a miRNA study of 51 ESs, 20 rhabdoid tumors (RTs), 20 synovial sarcomas (SSs), 15 malignant peripheral nerve sheath tumors (MPNSTs), 11 myoepithelial carcinomas (MECs), and 10 extraskeletal myxoid chondrosarcomas (EMCSs) with complete/partial loss of SMARCB1 nuclear immunostain, in contrast to controls (SMARCB1-immunopositive) of 96 STSs, 13 melanomas and 10 sarcomatoid carcinomas. The SMARCB1 genetic status of ESs was determined by MLPA and FISH. A subset of ESs (5/51) showed biallelic deletion of SMARCB1 with no overexpression of any miRNA, suggesting these tumors could be the counterpart of pediatric RT, at least genetically. Another subset (5/51) was genetically either intact or monoallelic deleted with at least threefold overexpression of one of miR-206,-381,-671-5p, suggesting epigenetic regulation only. 39/51 ESs had a biallelic deletion (>20% by FISH and/or by MLPA) but with overexpressed miR-206,-381, and 671-5p, suggesting intratumoral heterogeneity, i.e., both genetic and epigenetic regulation. At least threefold overexpression of one of miR-206,-381, and 671-5p was detected in all MPNSTs, EMCSs, SSs and 7 MCs. Except for ESs, four SSs and one MPNST, there was no event above threefold overexpression of miR-765 among all 195 tested tumors. Our results suggest a general role of miR-206,-381, and 671-5p in SMARCB1 gene silencing of ES, MC, EMCS, MPNST and SS. In the future, miR-765 could possibly be a diagnostic tool for ES because of its 97% specificity and 80% sensitivity. © 2016 Wiley Periodicals, Inc.

Targeting EZH2-mediated methylation of H3K27 inhibits proliferation and migration of Synovial Sarcoma in vitro

Synovial sarcoma is an aggressive soft tissue sarcoma genetically defined by the fusion oncogene SS18-SSX. It is hypothesized that either SS18-SSX disrupts SWI/SNF complex inhibition of the polycomb complex 2 (PRC2) methyltransferase Enhancer of Zeste Homologue 2 (EZH2), or that SS18-SSX is able to directly recruit PRC2 to aberrantly silence target genes. This is of potential therapeutic value as several EZH2 small molecule inhibitors are entering early phase clinical trials. In this study, we first confirmed EZH2 expression in the 76% of human synovial sarcoma samples. We subsequently investigated EZH2 as a therapeutic target in synovial sarcoma in vitro. Knockdown of EZH2 by shRNA or siRNA resulted in inhibition of cell growth and migration across a series of synovial sarcoma cell lines. The EZH2 selective small-molecule inhibitor EPZ005687 similarly suppressed cell proliferation and migration. These data support the hypothesis that targeting EZH2 may be a promising therapeutic strategy in the treatment of synovial sarcoma; clinical trials are initiating enrollment currently.

Expression of F-actin-capping protein subunit beta, CAPZB, is associated with cell growth and motility in epithelioid sarcoma

BACKGROUND

A previous proteomics study demonstrated the overexpression of F-actin capping protein subunit beta (CAPZB) in tissue specimens of epithelioid sarcoma (EpiS). The aim of the present study was to elucidate the function of CAPZB in EpiS.

METHODS

Cellular functional assays were performed in two EpiS cell lines using CAPZB siRNAs. In addition, comparative protein expression analyses using Isobaric Tags for Relative and Absolute Quantitation (i-TRAQ) method were performed to identify the specific proteins whose expression was dysregulated by CAPZB, and analysed the data with the Ingenuity Pathways Analysis (IPA) system using the obtained protein profiles to clarify the functional pathway networks associated with the oncogenic function of CAPZB in EpiS. Additionally, we performed functional assays of the INI1 protein using INI1-overexpressing EpiS cells.

RESULTS

All 15 EpiS cases showed an immunohistochemical expression of CAPZB, and two EpiS cell lines exhibited a strong CAPZB expression. Silencing of CAPZB inhibited the growth, invasion and migration of the EpiS cells. Analysis of protein profiles using the IPA system suggested that SWI/SNF chromatin-remodeling complexes including INI1 may function as a possible upstream regulator of CAPZB. Furthermore, silencing of CAPZB resulted in a decreased expression of INI1 proteins in the INI1-positive EpiS cells, whereas the induction of INI1 in the INI1-deficient EpiS cells resulted in an increased CAPZB mRNA expression.

CONCLUSIONS

CAPZB is involved in tumor progression in cases of EpiS, irrespective of the INI1 expression, and may be a potential therapeutic target. The paradoxical relationship between the tumor suppressor INI1 and the oncoprotein CAPZB in the pathogenesis of EpiS remains to be clarified.

Epithelioid Sarcoma: Diagnostic Features and Genetics

Epithelioid sarcoma (ES) is a rare, aggressive soft-tissue neoplasm of uncertain differentiation, characterized by nodular aggregates of epithelioid cells, which are immunoreactive to cytokeratins (CKs) and epithelial membrane antigen, and often for CD34. It has a propensity for multifocal disease at presentation, local recurrence, and regional metastasis. These are aggressive neoplasms with particularly poor prognosis after regional or distant metastatic disease, for which surgical resection is still the mainstay of treatment, and options for patients with metastatic disease remain undefined. There are 2 distinct variants: classic ES, which typically presents as a subcutaneous or deep dermal mass in the distal extremities of young adults and comprises nodular distributions of relatively uniform epithelioid cells with central necrosis, and the proximal variant, which has a predilection for proximal limbs and limb girdles and the midline of the trunk, which is composed of sheets of larger, more atypical cells with variable rhabdoid morphology. Both classic and proximal-type ESs are associated with the loss of SMARCB1/INI1 protein expression, but appear otherwise molecularly relatively heterogeneous. We review classic and proximal-type ES, discussing morphology, immunohistochemical and genetic findings, the differential diagnosis, and the future potential for targeted therapies.

The genomic landscape of epithelioid sarcoma cell lines and tumours

We carried out whole genome and transcriptome sequencing on four tumour/normal pairs of epithelioid sarcoma. These index cases were supplemented with whole transcriptome sequencing of three additional tumours and three cell lines. Unlike rhabdoid tumour (the other major group of SMARCB1-negative cancers), epithelioid sarcoma shows a complex genome with a higher mutational rate, comparable to that of ovarian carcinoma. Despite this mutational burden, SMARCB1 mutations remain the most frequently recurring event and are probably critical drivers of tumour formation. Several cases show heterozygous SMARCB1 mutations without inactivation of the second allele, and we explore this further in vitro. Finding CDKN2A deletions in our discovery cohort, we evaluated CDKN2A protein expression in a tissue microarray. Six out of 16 cases had lost CDKN2A in greater than or equal to 90% of cells, while the remaining cases had retained the protein. Expression analysis of epithelioid sarcoma cell lines by transcriptome sequencing shows a unique profile that does not cluster with any particular tissue type or with other SWI/SNF-aberrant lines. Evaluation of the levels of members of the SWI/SNF complex other than SMARCB1 revealed that these proteins are expressed as part of a residual complex, similarly to previously studied rhabdoid tumour lines. This residual SWI/SNF is susceptible to synthetic lethality and may therefore indicate a therapeutic opportunity.

The diagnostic utility of reduced immunohistochemical expression of SMARCB1 in synovial sarcomas: a validation study

Synovial sarcoma is a malignant mesenchymal neoplasm of uncertain histogenesis, characterized by a specific SS18-SSX fusion. The diagnosis of synovial sarcoma can be challenging based on morphology and conventional immunohistochemistry alone, and identification of the fusion gene by molecular genetics may be necessary for diagnosis. Several recent studies have demonstrated the diagnostic utility of the reduced expression of SMARCB1 in synovial sarcomas as measured using immunohistochemistry. Therefore, we undertook a validation study using synovial sarcomas and other spindle or round cell tumors that could enter differential diagnosis of monophasic or poorly differentiated synovial sarcomas. Among 36 synovial sarcomas that were successfully evaluated, the expression of SMARCB1 was diffusely reduced in 33 cases (92%) at variable degrees. In contrast, the expression of SMARCB1 was not reduced in any of the 93 evaluable non-synovial sarcoma tumors (5 thymomas, 5 sarcomatoid mesotheliomas, 10 schwannomas, 9 mesenchymal chondrosarcomas, 20 solitary fibrous tumors, 19 Ewing sarcomas, and 25 malignant peripheral nerve sheath tumors). A few schwannomas and malignant peripheral nerve sheath tumors showed mosaic or complete loss of SMARCB1 expression. Reduced expression of SMARCB1 immunoreactivity was therefore found to be highly sensitive and specific for synovial sarcoma, and can be useful for rapidly and accurately confirming the diagnosis of synovial sarcoma. This reduction in SMARCB1 expression likely reflects the BAF47 ejection mechanism of the SS18-SSX fusion product and can therefore be viewed as an indirect visualization of this fusion product.

Epithelioid Sarcoma: Opportunities for Biology-Driven Targeted Therapy

Epithelioid sarcoma (ES) is a soft tissue sarcoma of children and young adults for which the preferred treatment for localized disease is wide surgical resection. Medical management is to a great extent undefined, and therefore for patients with regional and distal metastases, the development of targeted therapies is greatly desired. In this review, we will summarize clinically relevant biomarkers (e.g., SMARCB1, CA125, dysadherin, and others) with respect to targeted therapeutic opportunities. We will also examine the role of EGFR, mTOR, and polykinase inhibitors (e.g., sunitinib) in the management of local and disseminated disease. Toward building a consortium of pharmaceutical, academic, and non-profit collaborators, we will discuss the state of resources for investigating ES with respect to cell line resources, tissue banks, and registries so that a roadmap can be developed toward effective biology-driven therapies.

Vulvar sarcomas: Short guideline for histopathological recognition and clinical management. Part 1

Malignant tumors of the female reproductive system are a serious health and social problem, as they are the second most common cause of death among women, after breast cancer. Their incidence has increased dramatically during recent years, probably due to the different sexual habits and changes in the prevalence of HIV/ AIDS and HPV virus carriers, among other factors. Vulvar tumors represent only 4% of all gynecological neoplasms, and they are fourth in frequency after tumors of the cervix, uterus, and ovary. Ninety eight percent of all vulvar tumors are benign and only 2% are malignant. The overall incidence of tumors with vulvar location is between two and seven cases per 100,000 women, and it increases with age, while the death rate is estimated at 0.7 per 100,000 women. Sarcomas of the vulva comprise approximately 1-3% of all vulvar cancers, with leiomyosarcomas, epithelioid sarcomas, and rhabdomyosarcomas being the most common among them. They are characterized by rapid growth, high metastatic potential, frequent recurrences, aggressive behavior, and high mortality rate. In this paper, we present the most common forms of sarcomas of the vulva (leiomyosarcoma, epithelioid sarcoma, malignant rhabdoid tumor, rhabdomyosarcoma) in order to emphasize the broad differential diagnosis, rare appearance, non-specific clinical picture, aggressive course, and high mortality.

Penile pseudomyogenic hemangioendothelioma/epithelioid sarcoma-like hemangioendothelioma with a novel pattern of SERPINE1-FOSB fusion detected by RT-PCR--report of a case

We experienced a rare case of penile mesenchymal tumor in a 43-year-old Japanese man. At least three nodules were observed around the penis. The tumors were composed of spindle- to oval-shaped atypical cells with and without prominent nucleoli. These cells were like myogenic cells, but negative for myogenic markers. They were positive for endothelial markers, such as ERG, Fli1 and CD31. They were also positive for nuclear and cytoplasmic FOSB which are not expressed in epithelioid hemangioendothelioma or epithelioid sarcoma. These pathological and immunohistochemical findings strongly suggested pseudomyogenic hemangioendothelioma/epithelioid sarcoma-like hemangioendothelioma (PHE/ES-HE). Since a recent report directly proved that two cases of PHE/ES-HE have SERPINE1-FOSB fusion gene by reverse transcription-polymerase chain reaction (RT-PCR), we examined whether the fusion gene is present or not in the present case by RT-PCR using fresh frozen surgical material. Sequencing of the PCR product revealed that this case has SERPINE1-FOSB fusion. The fusion pattern of our case was different from those of two previously reported cases. In our case, 86 nucleotides of SERPINE1 intron 1 were inserted between SERPINE1 exon 1 and the middle portion of FOSB exon 1, and a putative translation start codon was identified in SERPINE1 intron 1. Thus, this is the third case of PHE/ES-HE with SERPINE1-FOSB fusion proved by RT-PCR.

Extraskeletal myxoid chondrosarcoma presenting as an intradural spinal mass: report of a rare clinical presentation with an emphasis on differential diagnostic considerations

Extraskeletal myxoid chondrosarcoma is a rare soft tissue neoplasm that occurs predominantly in the soft tissues of the lower extremities. Herein we present a case of a 29 year old male who presented with bilateral femoral numbness believed to be the result of prior injury to his back. A magnetic resonance imaging revealed a mass in the T4-T5 epidural space compressing the spinal cord. Laminectomy was performed and the lesion removed piecemeal. The pathology specimen consisted of multiple fragments of dura involved by a myxoid neoplasm with a nodular growth pattern. The tumor cells were arranged in anastomosing cords and strands. Individual tumor cells were small, of uniform size and shape, with small hyperchromatic nuclei and scant eosinophilic cytoplasm. Immunohistochemical stains were performed which showed the tumor cells were diffusely positive for vimentin and focally positive for EMA, S-100 protein and cytokeratin, whereas they were negative for CD34 and CD99. Fluorescence in situ hybridization (FISH) studies showed a clonal population of cells with re-arrangement of the EWSR1 locus, confirming the histologic impression of extraskeletal myxoid chondrosarcoma. This is the first report of a case of an extraskeletal myxoid chondrosarcoma arising from the dura, confirmed to have rearrangement of the EWSR1 gene by FISH. There have only been two other cases of dural based extraskeletal myxoid chondrosarcoma reported prior to our case. We also briefly review the published literature and discuss differential diagnostic considerations for this rare tumor.

The expanding family of SMARCB1(INI1)-deficient neoplasia: implications of phenotypic, biological, and molecular heterogeneity

Since the description of atypical teratoid/rhabdoid tumors of the central nervous system and renal/extrarenal malignant rhabdoid tumors in children, the clinicopathologic spectrum of neoplasms having in common a highly variable rhabdoid cell component (0% to 100%) and consistent loss of nuclear SMARCB1 (INI1) expression has been steadily expanding to include cribriform neuroepithelial tumor of the ventricle, renal medullary carcinoma and a subset of collecting duct carcinoma, epithelioid sarcoma, subsets of miscellaneous benign and malignant soft tissue tumors, and rare rhabdoid carcinoma variants of gastroenteropancreatic, sinonasal, and genitourinary tract origin. Although a majority of SMARCB1-deficient neoplasms arise de novo, the origin of SMARCB1-deficient neoplasia in the background of a phenotypically or genetically definable differentiated SMARCB1-intact "parent neoplasm" has been convincingly demonstrated, highlighting the rare occurrence of rhabdoid tumors as "double-hit neoplasia." As a group, SMARCB1-deficient neoplasms occur over a wide age range (0 to 80 y), may be devoid of rhabdoid cells or display uniform rhabdoid morphology, and follow a clinical course that varies from benign to highly aggressive causing death within a few months irrespective of aggressive multimodality therapy. Generally applicable criteria that would permit easy recognition of these uncommon neoplasms do not exist. Diagnosis is based on site-specific and entity-specific sets of clinicopathologic, immunophenotypic, and/or molecular criteria. SMARCB1 immunohistochemistry has emerged as a valuable tool in confirming or screening for SMARCB1-deficient neoplasms. This review summarizes the different phenotypic and topographic subgroups of SMARCB1-deficient neoplasms including sporadic and familial, benign and malignant, and rhabdoid and nonrhabdoid variants, highlighting their phenotypic heterogeneity and molecular complexity.

Differential SALL4 immunoexpression in malignant rhabdoid tumours and epithelioid sarcomas

AIMS

Malignant rhabdoid tumours (MRTs) and epithelioid sarcomas (ESs) are distinctive malignant neoplasms with characteristic clinicopathological features. However, these two tumour types share some phenotypic features, such as epithelioid/rhabdoid cytology, expression of epithelial markers, and immunohistochemical loss of INI1. The distinction can be problematic in atypical clinical settings, and ancillary diagnostic tools are needed. The expression of CD34 is widely cited as favouring the diagnosis of ES, but no formal comparative study has been performed in the post-INI1 era. Here, we evaluated the utility of SALL4 for differentiating MRTs from ESs, and compared its performance with that of CD34.

METHODS AND RESULTS

Fifteen MRTs and 36 ESs were retrieved. All MRTs and ESs lacked INI1 reactivity, except for one MRT that lacked BRG1. A representative slide from each case was stained using antibodies against SALL4 and CD34. Ten (67%) of the 15 MRTs expressed SALL4. In contrast, only one (3%) of the 36 ESs expressed SALL4. CD34 staining was observed in nine (60%) of the MRTs and 29 (81%) of the ESs.

CONCLUSIONS

Despite moderate sensitivity, SALL4 expression may aid in distinguishing MRTs from ESs. CD34 was found to have questionable utility in making such distinctions.

SWI/SNF chromatin remodeling and human malignancies

The SWI/SNF complexes, initially identified in yeast 20 years ago, are a family of multi-subunit complexes that use the energy of adenosine triphosphate (ATP) hydrolysis to remodel nucleosomes. Chromatin remodeling processes mediated by the SWI/SNF complexes are critical to the modulation of gene expression across a variety of cellular processes, including stemness, differentiation, and proliferation. The first evidence of the involvement of these complexes in carcinogenesis was provided by the identification of biallelic, truncating mutations of the SMARCB1 gene in malignant rhabdoid tumors, a highly aggressive childhood cancer. Subsequently, genome-wide sequencing technologies have identified mutations in genes encoding different subunits of the SWI/SNF complexes in a large number of tumors. SWI/SNF mutations, and the subsequent abnormal function of SWI/SNF complexes, are among the most frequent gene alterations in cancer. The mechanisms by which perturbation of the SWI/SNF complexes promote oncogenesis are not fully elucidated; however, alterations of SWI/SNF genes obviously play a major part in cancer development, progression, and/or resistance to therapy.

Malignant extra renal rhabdoid tumour presenting as central airway obstruction

Rhabdoid tumours are one of the most aggressive childhood neoplasms associated with high mortality. The commonest age group affected is children less than five years of age. Rhabdoid tumour presenting as an endoluminal tracheal mass leading to central airway obstruction has not been previously reported. We describe the case of a 17-year-old male patient where malignant rhabdoid tumour masqueraded as bronchial asthma leading to a delayed diagnosis of upper airway obstruction by tracheal growth. Histopathological examination and immunohistochemistry confirmed the diagnosis of malignant rhabdoid tumour.

Differential microRNA expression profiles between malignant rhabdoid tumor and epithelioid sarcoma: miR193a-5p is suggested to downregulate SMARCB1 mRNA expression

Malignant rhabdoid tumor and epithelioid sarcoma are classified as tumors of uncertain differentiation. However, it is controversial whether these tumors are distinct entities because they share similar histological and immunohistochemical features such as the existence of rhabdoid cells or complete loss of SMARCB1 protein expression. MicroRNAs are small non-coding RNAs, and it is suggested that knowledge of microRNA expression profiles in cancer may have substantial value for diagnostics. We first analyzed microRNA expression profiles in 13 frozen materials (five malignant rhabdoid tumors, two proximal type epithelioid sarcomas, and six conventional type epithelioid sarcomas) and subsequently examined the specific microRNA expressions in 29 paraffin-embedded materials (8 malignant rhabdoid tumors, 13 proximal type epithelioid sarcomas, and 8 conventional type epithelioid sarcomas) and 13 previously described frozen materials by quantitative RT-PCR. According to the unsupervised hierarchical clustering of microRNA, proximal type epithelioid sarcoma and conventional type epithelioid sarcoma were classified into the same category, whereas malignant rhabdoid tumor was a distinct category from both types of epithelioid sarcoma. In addition, when malignant rhabdoid tumor with SMARCB1 gene alterations and proximal type and conventional type epithelioid sarcoma with no SMARCB1 gene alterations were compared, 56 microRNAs were isolated as being significantly different (ANOVA, P<0.05). Among them, quantitative RT-PCR using frozen and paraffin-embedded materials demonstrated that expression levels of miR193a-5p (P=0.002), which has been suggested to downregulate SMARCB1 mRNA expression, showed statistically different expression levels between malignant rhabdoid tumor and epithelioid sarcoma with no SMARCB1 gene alterations. These results suggest that epithelioid sarcoma, especially proximal type epithelioid sarcoma, and malignant rhabdoid tumor are distinct tumors with respect to the microRNA expression profiles and that miR193a-5p may have an important role in the inhibition of SMARCB1 mRNA expression.

Role of epigenetic modulation for the treatment of sarcoma

OPINION STATEMENT

Sarcoma is a disease that includes many different subtypes that can present with a wide range of differing clinical findings, prognosis, and treatment options. For certain subsets (e.g., Ewing sarcoma, osteosarcoma, rhabdomyosarcoma, gastrointestinal stromal tumor [GIST]), extensive clinical trials have delineated effective treatment regimens often involving combination therapy, including surgery, radiation, systemic chemotherapy, and small molecular inhibitors of tyrosine kinases (as in the case of GIST). For nearly all patients with sarcoma who have relapsed or developed metastasis, the therapeutic benefit of chemotherapy has reached a plateau and as such new treatment approaches are needed to move this field forward. We recommend that all patients have the opportunity to participate in clinical trials where available. Recently, in our clinic we have started to increase our use of molecular testing and DNA sequencing studies to help identify potential treatment options for patients. One area of evolving basic and clinical research in sarcomas is the field of epigenetic therapeutics. The enclosed article reviews the basics of epigenetics and highlights some completed and ongoing clinical trials of epigenetic treatments in sarcoma. We anticipate in the future that diagnostic platforms will be developed to help clinicians determine if an epigenetic therapy could be effective for an individual patient with sarcoma.

Consistent SMARCB1 homozygous deletions in epithelioid sarcoma and in a subset of myoepithelial carcinomas can be reliably detected by FISH in archival material

Epithelioid sarcomas (ES) are mesenchymal neoplasms subclassified into distal and proximal subtypes based on their distinct clinical presentations and histologic features. Consistent loss of SMARCB1 nuclear expression has been considered as the hallmark abnormality for both subtypes, a feature shared with atypical teratoid/rhabdoid tumor of infancy (ATRT). While virtually all ATRTs harbor underlying SMARCB1 somatic or germline alterations, mechanisms of SMARCB1 inactivation in ES are less well defined. To further define mechanisms of SMARCB1 inactivation a detailed molecular analysis was performed on 40 ES (25 proximal and 15 distal ES, with classic morphology and negative SMARCB1 expression) for their genomic status of SMARCB1 and related genes encoding the SWI/SNF subunits (PBRM1, BRG1, BRM, SMARCC1/2 and ARID1A) by FISH using custom BAC probes. An additional control group was included spanning a variety of 41 soft tissue neoplasms with either rhabdoid/epithelioid features or selected histotypes previously shown to lack SMARCB1 by IHC. Furthermore, 12 ES were studied by array CGH (aCGH) and an independent TMA containing 50 additional ES cases was screened for Aurora Kinase A (AURKA) and cyclin D1 immunoexpression. Homozygous SMARCB1 deletions were found by FISH in 36/40 ES (21/25 proximal-type). One of the distal-type ES displayed homozygous SMARCB1 deletion in the tumor cells, along with a heterozygous deletion within normal tissue, finding confirmed by array CGH. None of the proximal ES lacking homozygous SMARCB1 deletions displayed alterations in other SWI/SNF subunits gene members. Among controls, only the SMARCB1-immunonegative myoepithelial carcinomas displayed SMARCB1 homozygous deletions in 3/5 cases, while no gene specific abnormalities were seen among all other histologic subtypes of sarcomas tested regardless of the SMARCB1 protein status. There was no consistent pattern of AURKA and Cyclin D1 expression. The array CGH was successful in 9/12 ES, confirming the SMARCB1 and other SWI/SNF genes copy numbers detected by FISH. Our study confirms the shared pathogenesis of proximal and distal ES, showing consistent SMARCB1 homozygous deletions. Additionally we report the first ES case associated with a SMARCB1 constitutional deletion, establishing a previously undocumented link with ATRT. Alternative mechanisms of SMARCB1 inactivation in SMARCB1-disomic ES remain to be identified, but appear unrelated to large genomic abnormalities in other SWI/SNF subunits.

Selected topics in the pathology of epithelioid soft tissue tumors

Epithelioid morphology, mimicking carcinoma, is a key or defining feature of several soft tissue tumors and may be seen in a wide variety of other tumors. This review will focus on those tumors defined at least in part by their epithelioid morphology, in particular epithelioid sarcoma, epithelioid malignant peripheral nerve sheath tumor, and sclerosing epithelioid fibrosarcoma. The role of loss of the SMARCB1 tumor-suppressor gene in the pathogenesis of these epithelioid soft tissue tumors will be discussed, as will their differential diagnosis with non-mesenchymal tumors, in particular carcinoma and melanoma.

Prognostic value of MIB-1, p53, epidermal growth factor receptor, and INI1 in childhood chordomas

BACKGROUND

Chordomas are slow-growing tumors and most commonly involve the sacrum and clivus. Multiple recurrences are frequent. Childhood chordomas are rare and often show exceptionally aggressive behavior, resulting in short survival and a high incidence of metastatic spread.

OBJECTIVE

This study examined the histologic features and immunohistochemical profile of pediatric chordomas and compared them with their adult counterparts.

METHODS

Nine pediatric and 13 adult cases were included in the study. Childhood chordomas were classified into conventional, atypical, and poorly differentiated types. Immunohistochemistry was performed for cytokeratin, epithelial membrane antigen, vimentin, S100, brachyury, p53, INI1, epidermal growth factor receptor (EGFR), and CD117. Cytogenetic analyses were performed in a subset of tumors for SMARCB1/INI1 locus on 22q chromosome by fluorescent in situ hybridization (FISH) and analysis of the SMARCB1/INI1 gene sequence.

RESULTS

All tumors showed expression of cytokeratin, epithelial membrane antigen, S100, vimentin, brachyury, and EGFR. Atypical morphology, p53 expression, higher MIB-1 labelling index (LI), and INI1 loss were more frequently seen in pediatric chordomas as compared with adults. None of the tumors showed CD117 expression. No point mutation in the SMARCB1/INI1 gene was noted in the tumors examined; however, 4 pediatric and 1 adult chordoma showed loss of this locus on FISH analysis.

CONCLUSIONS

A subset of pediatric chordomas with atypical histomorphologic features needs to be identified, as they behave in an aggressive manner and require adjuvant therapy. Pediatric chordomas more frequently show p53 expression, INI1 loss, and higher MIB-1 LI as compared with adults, whereas EGFR expression is common to both.

SMARCB1 expression in epithelioid sarcoma is regulated by miR-206, miR-381, and miR-671-5p on Both mRNA and protein levels

Proximal type epithelioid sarcoma shares similarities with malignant rhabdoid tumor, including the lack of nuclear immunoreactivity of SMARCB1. Biallelic mutation of SMARCB1 has been convincingly established as the cause of loss of protein expression in rhabdoid tumor, but the cause in epithelioid sarcoma remains unknown. In our previous work, we demonstrated that DNA hypermethylation and post-translational modification mechanisms were not involved. In this current work, we explored the hypothesis that miRNAs regulate SMARCB1 gene expression in epithelioid sarcomas. In silico target prediction analysis revealed eight candidate miRNAs, and quantitative PCR-in 32 formalin-fixed, paraffin-embedded tumor samples comprising 30 epithelioid sarcomas and two malignant rhabdoid tumors-demonstrated significant (P < 0.001) overexpression of four miRNAs in epithelioid sarcomas: miR-206, miR-381, miR-671-5p, and miR-765. Two human tumors (fibrosarcoma and colon adenocarcinoma) and a normal cell line (human dermal fibroblast) with retained SMARCB1 expression were cultured for miRNA transient transfection (electroporation) experiments. SMARCB1 mRNA expression was analyzed by quantitative real-time PCR and immunostaining of SMARCB1 was performed to examine the effect of miRNAs transfections on both RNA and protein levels. Only three of the overexpressed miRNAs (miR-206, miR-381, and miR-671-5p) could silence the SMARCB1 mRNA expression in cell cultures; most effectively miR-206. Transfection of miR-206, miR-381, miR-671-5p, and some combination of them also eliminated SMARCB1 nuclear staining, demonstrating a strong effect on not only mRNA but also protein levels. Our results suggest loss of SMARCB1 protein expression in epithelioid sarcoma is due to the epigenetic mechanism of gene silencing by oncomiRs.