"Proximal-type" epithelioid sarcoma, a distinctive aggressive neoplasm showing rhabdoid features. Clinicopathologic, immunohistochemical, and ultrastructural study of a series

Proximal-type epithelioid sarcoma: a new case report and literature review

Proximal-type epithelioid sarcoma is a rare soft tissue neoplasm which arises from the more proximal part of body and occurs more often in young people; the definite diagnosis depends mainly on the pathological examination; early detection and complete excision remain the foundation of treatment. Due to its aggressive behavior, high capacity of recurrence and the great ability to metastasize, a careful clinical long-term monitoring is required. We report a new case of a 20 years old girl, presented with proximal-type epithelioid sarcoma in her right scapular region, confirmed by pathological examination and removed surgically without recurrence or metastasis at eighteen months of follow-up.

Diagnostically Challenging Epithelioid Soft Tissue Tumors

In this article, we focus on the histologic features, differential diagnosis, and potential pitfalls in the diagnosis of epithelioid sarcoma, alveolar soft part sarcoma, clear-cell sarcoma, ossifying fibromyxoid tumor, and malignant extrarenal rhabdoid tumor. Numerous other soft tissue tumors also may have epithelioid variants or epithelioid features. Examples include epithelioid angiosarcoma, epithelioid malignant peripheral nerve sheath tumor, epithelioid gastrointestinal stromal tumor, and perivascular epithelioid cell tumor, among others.

Primary proximal epithelioid sarcoma of the lung successfully treated with pneumonectomy and adjuvant chemotherapy

Primary sarcomas of the lung and proximal epithelial sarcomas (PESs) are extremely rare. Inactivation of INI1 has been found in the majority of epithelioid sarcoma (ES). We report the third known case of a primary PES of the lung along with immunohistochemical data. A 41-year-old man with HIV infection, on highly active antiretroviral therapy, presented with haemoptysis, shortness of breath and progressive weight loss for 2 months. He was eventually diagnosed with stage IIA cT2bN0M0 grade-2 primary PES of the lung. This patient underwent pneumonectomy and adjuvant chemotherapy with ifosfamide and doxorubicin. He remains in remission 36 months since diagnosis. Our case stands to help other clinicians as treatment of such rare cases is often reliant on case reports. We also posit a possible pathogenic mechanism given a history of HIV infection in this patient. The association of INI1 mutation with other atypical sarcomas in patients with HIV infection merits further evaluation.

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.

Myoepithelioma-like Tumors of the Vulvar Region: A Distinctive Group of SMARCB1-deficient Neoplasms

We describe 9 tumors that resemble soft tissue myoepitheliomas but possess certain traits that do not fit perfectly into this category. These tumors, herein referred to as "myoepithelioma-like tumors of the vulvar region," occurred in the subcutis of the vulva and surrounding regions of adult women aged 24 to 65 years. Histologically, the tumors measured 2 to 7.7 cm and were well circumscribed, focally encapsulated, and lobulated. Tumor cells had an epithelioid to spindled shape, with fine amphophilic cytoplasm, and uniform nuclei with vesicular chromatin and nucleoli. The tumor stroma was relatively hypervascular, and comprised a mixture of myxoid and nonmyxoid components. Myxoid areas accounted for <5% to 95% of the tumor volume, wherein cells proliferated singly or in a loosely cohesive manner. In nonmyxoid areas, tumors cells grew in diffuse sheets or storiform arrangements. Immunohistochemically, all tested tumors were positive for vimentin, epithelial membrane antigen, and estrogen receptor; most tumors expressed actin. All tumors were negative for S100 protein, glial fibrillary acidic protein, and CD34. Cytokeratin expression was absent in all but 2 tumors, which showed rare positivity. SMARCB1 expression was deficient in all cases. EWSR1, FUS, and NR4A3 rearrangements were absent. All tumors were treated through surgery. Although 3 tumors regrew or recurred after intralesional excision, all 9 patients were alive without metastases at a mean follow-up of 66 months. Myoepithelioma-like tumors of the vulvar region constitute a distinct group of tumors, although future research is required to determine whether they are an unusual subtype of soft tissue myoepitheliomas or a separate disease.

HDAC Inhibition for the Treatment of Epithelioid Sarcoma: Novel Cross Talk Between Epigenetic Components

Epithelioid sarcoma is a rare neoplasm uniquely comprised of cells exhibiting both mesenchymal and epithelial features. Having propensity for local and distant recurrence, it poses a diagnostic dilemma secondary to pathologic complexity. Patients have dismal prognosis due to lack of effective therapy. HDAC inhibitors (HDACi) exhibit marked antitumor effects in various malignancies. The studies here demonstrate that pan-HDAC inhibitors constitute novel therapeutics versus epithelioid sarcoma. Human ES cells (VAESBJ, HS-ES, Epi-544) were studied in preclinical models to evaluate HDACi effects. Immunoblot and RT-PCR were used to evaluate expression of acetylated tubulin, histones H3/H4, EZH2 upon HDACi. MTS and clonogenic assays were used to assess the impact of HDACi on cell growth. Cell culture assays were used to evaluate the impact of HDACi and EZH2-specific siRNA inhibition on cell-cycle progression and survival. Unbiased gene array analysis was used to identify the impact of HDACi on epithelioid sarcoma gene expression. Xenografts were used to evaluate epithelioid sarcoma tumor growth in response to HDACi. HDAC inhibition increased target protein acetylation and abrogated cell growth and colony formation in epithelioid sarcoma cells. HDACi induced G(2) cell-cycle arrest and marked apoptosis, and reduced tumor growth in xenograft models. HDACi induced widespread gene expression changes, and EZH2 was significantly downregulated. EZH2 knockdown resulted in abrogated cell growth in vitro.

IMPLICATIONS

The current study suggests a clinical role for HDACi in human epithelioid sarcoma, which, when combined with EZH2 inhibitors, could serve as a novel therapeutic strategy for epithelioid sarcoma patients. Future investigations targeting specific HDAC isoforms along with EZH2 may potentially maximizing treatment efficacy.

SMARCA4 inactivation defines a group of undifferentiated thoracic malignancies transcriptionally related to BAF-deficient sarcomas

While investigating cohorts of unclassified sarcomas by RNA sequencing, we identified 19 cases with inactivation of SMARCA4, which encodes an ATPase subunit of BAF chromatin-remodeling complexes. Clinically, the cases were all strikingly similar, presenting as compressive mediastino-pulmonary masses in 30- to 35-year-old adults with a median survival time of 7 months. To help define the nosological relationships of these tumors, we compared their transcriptomic profiles with those of SMARCA4-mutated small-cell carcinomas of the ovary, hypercalcemic type (SCCOHTs), SMARCB1-inactivated malignant rhabdoid tumors (MRTs) and lung carcinomas (of which 10% display SMARCA4 mutations). Gene profiling analyses demonstrated that these tumors were distinct from lung carcinomas but related to MRTs and SCCOHTs. Transcriptome analyses, further validated by immunohistochemistry, highlighted strong expression of SOX2, a marker that supports the differential diagnosis of these tumors from SMARCA4-deficient lung carcinomas. The prospective recruitment of cases confirmed this new category of 'SMARCA4-deficient thoracic sarcomas' as readily recognizable in clinical practice, providing opportunities to tailor their therapeutic management.

Successful Treatment with Pazopanib for Multiple Lung Metastases of Inguinal Epithelioid Sarcoma: A Case Report

Epithelioid sarcoma is a rare soft tissue sarcoma and usually resistant to chemotherapy. It has high rates of local recurrence and distant metastasis, and the prognosis after metastasis is poor. We report a case of multiple lung metastases of an epithelioid sarcoma originating in the inguinal area that we treated with the multikinase inhibitor pazopanib. The patient was a 38-year-old male who began to experience discomfort in his left inguinal area. Magnetic resonance imaging showed a tumor extended from the medial aspect of the wing of the left ilium along the iliopsoas muscle to its site of insertion on the femur. The histopathological diagnosis with a biopsy was proximal-type epithelioid sarcoma. Although a positron emission tomography examination showed fluorodeoxyglucose accumulation in the left inguinal tumor, there was no distant metastasis. Wide resection by a combined iliac resection procedure was performed. Twelve months after surgery, computed tomography revealed multiple nodules and a diagnosis of bilateral multiple lung metastases was made. Treatment with pazopanib 800 mg was started. After 2.5 months of treatment, a clear reduction in the size of the pulmonary metastases was shown. Thirty months after the start of pazopanib treatment, most of the metastases have disappeared, and no development of new lesions has been seen. Therefore, it appeared that pazopanib was capable of serving as one of the choices of therapeutic agents that should be taken into consideration for the treatment of advanced epithelioid sarcoma.

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.

Cutaneous epithelioid malignant peripheral nerve sheath tumour: a clinicopathological analysis of 11 cases

AIMS

Epithelioid malignant peripheral nerve sheath tumour (E-MPNST) is a distinctive variant of malignant peripheral nerve sheath tumour characterized by the predominance of epithelioid cells, diffuse S100 positivity and infrequent association with neurofibromatosis type 1. The aim of this study was to further delineate clinicopathological features of cutaneous E-MPNST, correlate them with disease outcome and discuss differential diagnosis.

METHODS AND RESULTS

We analysed 11 cutaneous E-MPNSTs (six males, five females, median age 49 years, median size 1.6 cm). Tumours showed a predilection for lower extremities (45%) and trunk (45%), followed by upper extremity (9%). Follow-up was available for nine of 11 patients (range 24-100 months, median 52 months). Four patients had an uneventful clinical course (44%), two developed local recurrence(s) (22%) and three died due to disseminated disease (33%). No histological parameters were found to predict local recurrence(s), development of distant metastases or disease outcome, including size, percentage of epithelioid component, number of mitoses per 10 high-power fields, degree of nuclear atypia or site of occurrence (dermis, dermis/subcutis, subcutis) (P > 0.05). Immunohistochemically, all tumours were diffusely S100-positive, with a subset displaying loss of integrase interactor 1 (INI1) expression (50%).

CONCLUSIONS

Cutaneous E-MPNST has the potential to pursue an aggressive clinical course, associated with wide dissemination and unfavourable disease outcome.

Epithelioid malignant peripheral nerve sheath tumor: clinicopathologic analysis of 63 cases

Epithelioid malignant peripheral nerve sheath tumor (EMPNST) is rare and differs from conventional malignant peripheral nerve sheath tumor by showing diffuse S-100 protein positivity, infrequent association with NF1, and occasional origin in a schwannoma. Loss of INI1 expression is seen in a subset of tumors. The purpose of this study was to further define clinicopathologic features and outcome data in a large series of EMPNST. Sixty-three cases were identified in consultation files. The patient group consisted of 33 men and 30 women; the median age was 44 years (range, 6 to 80 y). One patient was reported to have NF1. One patient had 3 seemingly separate primary EMPNSTs during his 12-year clinical course. The median tumor size was 3.0 cm (range, 0.4 to 20 cm), and tumors were located most frequently on the lower extremity (30/63; 48%) and trunk (16/63; 25%). Most tumors were superficial (5 dermal, 38 subcutaneous); 15 were subfascial, and 5 were visceral. Microscopically, tumors comprised a relatively uniform but clearly atypical population of epithelioid cells. The majority of tumors demonstrated a multilobular growth pattern, with lobules and nests surrounded by myxoid and/or fibrous stroma. Tumor cells were round, polygonal, or ovoid and had round vesicular nuclei and abundant amphophilic to palely eosinophilic cytoplasm. Focal spindled morphology was seen in one third of cases. Most tumors (55/63; 87%) showed marked cytologic atypia with irregular vesicular nuclei and prominent nucleoli. Mitotic rate ranged from 1 to 46/10 HPF (median, 5/10 HPF); atypical mitotic figures were seen in 7 cases. Necrosis was present in 17 tumors. Twelve tumors were associated with a nerve. Nine tumors arose in a schwannoma (6 conventional type, 3 epithelioid) and 1 in a neurofibroma (in the NF1 patient). All tumors expressed S-100 protein, and the majority showed strong and diffuse staining (87%; 55/63). There was no expression of the melanocytic markers Mart-1/Melan-A (0/58), HMB-45 (0/57), and MiTF (0/9). Other immunohistochemical results included variable staining for GFAP (24/40; 60%) and EMA (4/29; 14%), whereas keratin was consistently negative (0/33). INI1 expression was lost in 67% of tumors examined (35/52). Most tumors were treated by surgical resection; 13 also received chemotherapy and/or radiation. Follow-up data were available for 31 cases and ranged in duration from 3 months to 20 years (median, 36 mo). Twenty-two patients have no evidence of disease at the time of follow-up. Nine patients developed local recurrence, 3 of whom were reported to be disease-free at the time of latest follow-up (44 mo, 19 y, and 20 y). Five patients developed distant metastases, and 4 patients died of disease (including 2 with unresectable recurrent tumors). Recurrence, metastasis, and disease-related death were observed independent of anatomic site or depth. In summary, EMPNST is a morphologically distinct variant that most commonly affects adults on the lower extremity or trunk, although a wide age range and site distribution are seen. Most tumors arise in superficial soft tissue, are diffusely S-100 positive, and two thirds show INI1 loss. On the basis of available follow-up information there is a comparatively low risk for recurrence and metastasis, irrespective of tumor depth.

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.

Fine-needle aspiration cytology of recurrent epithelioid sarcoma of the foot: Role of immonocytochemistry in definitive diagnosis

Fine-needle aspirations (FNA) have played a crucial role in the diagnosis and follow-up of malignancies including sarcomas. However, relatively low specificity in the classification of sarcoma is the main limitation of FNA. Epithelioid sarcoma is a rare tumor of soft tissues. Very few individual case reports describing cytological features of epithelioid sarcoma have been documented in the literature. Here, we describe cytological features of epithelioid sarcoma with immunocytohistological correlation.

Extremely rare case of vulvar myxoid epithelioid sarcoma

Epithelioid sarcoma is a distinct sarcoma type with specific morphology and immunophenotype. An epithelioid sarcoma of the vulva is an extremely rare and aggressive tumor and most commonly occurs on the labia majora in women of reproductive age. Only few cases have been reported, especially with the presence of focal myxoid changes. Early diagnosis is difficult because of its benign appearance as a painless subcutaneous nodule. Optimal treatment is not well established due to its rarity. We report a successfully approached case of vulvar epithelioid sarcoma that occurred in a 34-year-old female patient, treated with wide local excision, and review of the current medical literature.

Prognostic Value of Relevant Clinicopathologic Variables in Epithelioid Sarcoma: A Multi-Institutional Retrospective Study of 44 Patients

Background

Epithelioid sarcoma (ES) is an extremely rare soft tissue sarcoma. Recently, the proximal variant has been reported to be a more aggressive subtype; however, as most reports of ES have involved small case series, the actual prognostic implications remain unclear. We investigated the clinicopathological features of patients with ES to identify the prognostic factors that influence survival.

Methods

We retrospectively analyzed the clinicopathological features of 44 patients with ES who had been treated at our institutions between 1991 and 2011. Among these patients, 26 were diagnosed histologically as having classic-type ES, whereas the remaining 18 had proximal-type ES. Thirty-three of the patients, all without distant metastases, underwent curative surgery, and the remaining 11 with distant metastases (M1) received palliative treatment.

Results

The proximal subtype was significantly correlated with a proximal tumor location, distant metastases at presentation, presence of rhabdoid cells, a higher tumor grade, and vascular invasion. The overall survival (OS) rate at 5 years for the 44 patients was 45 %. A superficial tumor location and lymph node metastases (N1) at presentation were independently predictive of local recurrence-free survival (LRFS), and N1 and M1 tumors were independently predictive of distant metastasis-free survival and OS, respectively. The proximal subtype was associated with unfavorable LRFS and OS, although not to a statistically significant degree.

Conclusions

Proximal-type ES has significantly more aggressive clinicopathological features than classic-type ES, and lymph node or distant metastasis has the most critical impact on prognosis.

Pancreatic undifferentiated rhabdoid carcinoma: KRAS alterations and SMARCB1 expression status define two subtypes

Pancreatic undifferentiated carcinoma is a heterogeneous group of neoplasms, including pleomorphic giant cell, sarcomatoid, round cell, and rhabdoid carcinomas, the molecular profiles of which have so far been insufficiently characterized. We studied 14 undifferentiated carcinomas with prominent rhabdoid cells, occurring as advanced tumors in seven females and seven males aged 44-96 years (mean: 65 years). Histologically, 10 tumors qualified as pleomorphic giant cell and 4 as monomorphic anaplastic carcinomas. A glandular component, either in the primary or in the metastases, was seen in 5 out of 14 tumors (4 out of 10 pleomorphic giant cell and 1 out of 4 monomorphic anaplastic subtypes, respectively). Osteoclast-like giant cells were absent. Immunohistochemistry revealed coexpression of cytokeratin and vimentin, and loss of membranous β-catenin and E-cadherin staining in the majority of cases. Nuclear SMARCB1 (INI1) expression was lost in 4 out of 14 cases (28%), representing all 4 tumors of the monomorphic anaplastic subtype. FISH and mutation testing of KRAS revealed KRAS amplification in 5 out of 13 (38%) and exon 2 mutations in 6 out of 11 (54%) successfully analyzed cases. A strong correlation was found between KRAS alterations (mutation and/or copy number changes) and intact SMARCB1 expression (7 out of 8; 87%). On the other hand, loss of SMARCB1 expression correlated with the absence of KRAS alterations (3 out of 5 cases; 60%). The results suggest that rhabdoid phenotype in pancreatic undifferentiated rhabdoid carcinomas has a heterogeneous genetic background. SMARCB1 loss is restricted to the anaplastic monomorphic subtype and correlates with the absence of KRAS alterations, whereas the pleomorphic giant cell subtype is characterized by KRAS alterations and intact SMARCB1 expression. Recognition and appropriate subtyping of these rare variants might become necessary for future therapeutic strategies.

Rhabdoid tumor predisposition syndrome

Rhabdoid tumors (RT), or malignant rhabdoid tumors, are among the most aggressive and lethal forms of human cancer. They can arise in any location in the body but are most commonly observed in the brain, where they are called atypical teratoid/rhabdoid tumors (AT/RT), and in the kidneys, where they are called rhabdoid tumors of the kidney. The vast majority of rhabdoid tumors present with a loss of function in the SMARCB1 gene, also known as INI1, BAF47, and hSNF5, a core member of the SWI/SNF chromatin-remodeling complex. Recently, mutations in a 2nd locus of the SWI/SNF complex, the SMARCA4 gene, also known as BRG1, were found in rhabdoid tumors with retention of SMARCB1 expression. Familial cases may occur in a condition known as rhabdoid tumor predisposition syndrome (RTPS). In RTPS, germline inactivation of 1 allele of a gene occurs. When the mutation occurs in the SMARCB1 gene, the syndrome is called RTPS1, and when the mutation occurs in the SMARCA4 gene it is called RTPS2. Children presenting with RTPS tend to develop tumors at a younger age, but the impact that germline mutation has on survival remains unclear. Adults who carry the mutation tend to develop multiple schwannomas. The diagnosis of RTPS should be considered in patients with RT, especially if they have multiple primary tumors, and/or in individuals with a family history of RT. Because germline mutations result in an increased risk of carriers developing RT, genetic counseling for families with this condition is recommended.

[Epithelioid sarcoma of the orbit]

BACKGROUND

Sarcomas count among the very rare malignancies of the orbit. Epithelioid sarcomas typically occur in the subcutaneous tissue of younger patients; an affected orbit constitutes a rarity.

OBJECTIVES

Only three cases of this extremely rare disease of the orbit, which is associated with marked aggressiveness and a very poor prognosis, have been analysed in the worldwide current literature.

PATIENT AND METHODS

We present a case report together with a literature review. A rapidly progressing painful proptosis with visual loss occurred in a 30-year-old patient. Imaging and invasive diagnostic procedures were initiated as a consequence of this.

RESULTS

Diagnostic imaging revealed an infiltrative process of the right orbit. Following endonasal decompression of the orbit and probe acquisition, histological and immunohistochemical tests showed the presence of a proximal type epithelioid sarcoma. Therapy consisted of orbit exenteration together with implantation of titanium miniplates for orbital prosthesis. During the course of disease, osseous metastases developed. The patient died during palliative chemotherapy, 14 months after the initial diagnosis.

CONCLUSION

Epithelioid sarcomas are extremely rare, difficult to treat tumours in the head and neck region. The associated mortality rates are high. Aggressive surgical therapy with intensive follow-up is recommended. The prognosis depends upon the resection status.

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.

Myoepithelial tumor of soft tissue: histology and genetics of an evolving entity

Myoepithelial neoplasms represent a heterogeneous group of tumors of which classification is incomplete and evolving. Those of the soft tissues often form genetically distinct subgroups that differ from those arising within salivary glands. Soft-tissue myoepithelial tumors (including mixed tumors that show true glandular or ductal differentiation) exhibit a spectrum of different morphologic patterns, making them difficult to distinguish from a variety of other neoplasms. They have been increasingly shown to harbor genetic fusions involving EWSR1 and partner genes that are not seen in the well-characterized tumor classes involving EWSR1 translocations. We review the spectrum of soft-tissue myoepithelial tumors, discussing recent immunohistochemical and genetic findings and the differential diagnosis.

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.

Synovial sarcoma: defining features and diagnostic evolution

Synovial sarcoma (SS) is a malignant mesenchymal neoplasm with variable epithelial differentiation, with a propensity to occur in young adults and which can arise at almost any site. It is generally viewed and treated as a high-grade sarcoma. As one of the first sarcomas to be defined by the presence of a specific chromosomal translocation leading to the production of the SS18-SSX fusion oncogene, it is perhaps the archetypal "translocation-associated sarcoma," and its translocation remains unique to this tumor type. Synovial sarcoma has a variety of morphologic patterns, but its chief forms are the classic biphasic pattern, of glandular or solid epithelial structures with monomorphic spindle cells and the monophasic pattern, of fascicles of spindle cells with only immunohistochemical or ultrastructural evidence of epithelial differentiation. However, there is significant morphologic heterogeneity and overlap with a variety of other neoplasms, which can cause diagnostic challenge, particularly as the immunoprofile is varied, SS18-SSX is not detected in 100% of SSs, and they may occur at unusual sites. Correct diagnosis is clinically important, due to the relative chemosensitivity of SS in relation to other sarcomas, for prognostication and because of the potential for treatment with specific targeted therapies in the near future. We review SS, with emphasis on the diagnostic spectrum, recent immunohistochemical and genetic findings, and the differential diagnosis.

SMARCB1(INI1)-deficient sinonasal basaloid carcinoma: a novel member of the expanding family of SMARCB1-deficient neoplasms

Poorly differentiated sinonasal carcinomas are a heterogenous group of aggressive neoplasms that encompasses squamous cell carcinoma including basaloid variant, lymphoepithelial carcinoma, sinonasal undifferentiated carcinoma, and neuroendocrine-type small cell carcinoma. We herein describe 3 cases of a hitherto unreported variant combining features of basaloid carcinoma with variable intermingled rhabdoid cells. Patients were 2 women (aged 28 and 35) and a man (52 y) who presented with sinonasal masses. All had advanced local disease with bone involvement (pT4). None had a history of irradiation or a family history of rhabdoid tumors. Treatment was surgery and adjuvant chemoradiation. One patient developed liver, lung, pleural, and pericardial metastases (63 mo) and is currently (70 mo) alive under palliative treatment. Another developed recurrent cervical lymph node metastases and died of disease 8.5 years later. The youngest patient was disease-free at last follow-up 7 years later. Histologic features were very similar in all 3 cases and showed intimate admixture of compact basaloid cell nests with peripheral palisading, perivascular pseudorosettes, and a few scattered rhabdoid cells. Rhabdoid cells were more extensive in the metastasis in 1 case but formed a minor inconspicuous component in the primary tumors in all cases. Striking features common to all cases were (1) basaloid “blue” appearance at low power, (2) papilloma-like exophytic component, (3) extensive pagetoid surface growth with prominent denuding features, and (4) replacement of underlying mucous glands mimicking an inverted papilloma. Clear-cut origin from benign papilloma and overt squamous differentiation were lacking. Diffuse (2) or partial (1) p16 expression was noted, but all cases lacked human papillomavirus DNA by molecular tests. In situ hybridization was negative for Epstein-Barr virus. Immunohistochemistry showed diffuse expression of pancytokeratin. CK5 and vimentin showed intermingling of CK5⁺/vimentin⁻ basaloid and CK5⁻/vimentin⁺ rhabdoid cells. Complete loss of nuclear SMARCB1 expression was seen in all cases including also the denuding carcinoma in situ–like surface lesions. To our knowledge, this variant of sinonasal carcinoma has not been reported before. The identical features in all 3 cases suggest a specific disease rather than a nonspecific dedifferentiated phenotype. Awareness of this rare variant and thus reporting of additional cases is necessary for defining its full morphologic and biological spectrum.

Challenging epithelioid mesenchymal neoplasms: mimics and traps

Epithelioid mesenchymal malignancies represent a major diagnostic challenge. Epithelioid morphology can be observed in a variety of soft tissue neoplasms, however there exist specific subtypes in which an epithelioid apperance constitutes the most distinctive morphological feature. Moving from epithelioid sarcoma of Enzinger (the prototype of sarcoma with epithelioid morphology), this review will focus on the most relevant entities: namely epithelioid haemangioendothelioma and angiosarcoma, pseudomyogenic haemangioendothelioma, epithelioid malignant peripheral nerve sheath tumour, epithelioid sclerosing fibrosarcoma, epithelioid pleomorphic liposarcoma, alveolar soft part sarcoma, and undifferentiated soft tissue sarcoma with epithelioid morphology. Differential diagnoses and major pitfalls will be discussed in detail.

Concurrent loss of INI1, PBRM1, and BRM expression in epithelioid sarcoma: implications for the cocontributions of multiple SWI/SNF complex members to pathogenesis

The loss of INI1 (SMARCB1) expression, caused by SMARCB1 (INI1, SNF5L4, BAF47) inactivation, frequently occurs in epithelioid sarcoma (ES) and could aid in confirming the diagnosis. Except for INI1, the expression of switch in mating type/sucrose nonfermentation complex members in ES has never been examined. In this study, the expression of key subunits of this complex-INI1, BRG1 (SMARCA4), BRM (SNF2L2, SMARCA2), PBRM1 (hPB1, BAF180), and BAF155 (SMARCC1)-was analyzed in 23 ES cases: 15 conventional and 8 proximal type. All of the cases were reviewed and reclassified by hematoxylin-eosin staining and immunostaining for cytokeratin AE1/3, epithelial membrane antigen, CD34, vimentin, and INI1 expression. Of the 23 ES cases, 19 (82.6%) showed a loss of PBRM1, and 18 (78.3%), a loss of INI1. In most cases (17, 73.9%), loss of INI1 and PBRM1 expression was observed. The pattern of PBRM1 expression was similar to that of INI1, that is, not correlated with changes in cellular morphology. The concurrent loss of BRM, PBRM1, and INI1expression was detected in 2 cases with pure rhabdoid tumor features. The frequent observation of concurrent loss of INI1 and PBRM1 suggests that certain switch in mating type/sucrose nonfermentation complex components might act synergistically in the pathogenesis of ES by unknown mechanisms and that these components could provide new targets for therapy. The usefulness of PBRM1 as a biomarker of ES and its mechanism in ES require further investigation. Loss of BRM in ES with pure rhabdoid features suggests that BRM might be involved in the underlying mechanisms of this type of ES.

Rhabdoid Variant of Myoepithelial Carcinoma, with EWSR1 Rearrangement: Expanding the Spectrum of EWSR1-Rearranged Myoepithelial Tumors

Myoepithelial and mixed tumors represent a heterogeneous group of neoplasms for which classification is incomplete and continues to evolve. Those arising in the soft tissues appear to represent subgroups that are genetically distinct from those that occur within salivary glands. We describe a case of soft tissue myoepithelial carcinoma with rhabdoid morphology, which presented as an enlarging neck mass in a 40 year old male, and in which EWSR1 rearrangement was demonstrated by fluorescence in situ hybridization. This neoplasm showed diffuse INI1 loss, making distinction from other INI1-negative rhabdoid tumors difficult. This expands the range of reported histologic features of EWSR1-rearranged myoepithelial neoplasms, and highlights the significant morphologic and immunohistochemical overlap between this and other INI1-negative malignant rhabdoid neoplasms.

Primary sinonasal mucosal melanoma with aberrant diffuse and strong desmin reactivity: a potential diagnostic pitfall!

The broad morphologic spectrum, inherent immunophenotypic heterogeneity of malignant melanoma and its rarity in the sinonasal tract are major challenges in eliciting the correct diagnosis, which may lead to misclassification and inadequate medical management. Herein, we describe a single case of a 70 year-old male with sinonasal mucosal melanoma, exhibiting varying histologic phenotypes including small round blue cell morphology, epithelioid and focal rhabdoid morphology and strong, diffuse desmin immunoreactivity. These constellation of features initially prompted the diagnosis of rhabdomyosarcoma. The differential diagnosis in this anatomic area includes other malignant small round blue cell tumors of the sinonasal mucosa such as rhabdomyosarcoma, olfactory neuroblastoma, sinonasal undifferentiated carcinoma, and lymphoma. We reviewed precedent literature and further discuss the potential pitfalls to which pathologists may be prone.

Proximal-type epithelioid sarcoma -- case report

Epithelioid sarcoma, first described by Enzinger in 1970, is a rare soft-tissue sarcoma typically presenting as a subcutaneous or deep dermal mass in distal portions of the extremities of adolescents and young adults. In 1997, Guillou et al. described a different type of epithelioid sarcoma, called proximal-type epithelioid sarcoma, which is found mostly in the pelvic and perineal regions and genital tracts of young to middle-aged adults. It is characterized by a proliferation of epithelioid-like cells with rhabdoid features and the absence of a granuloma-like pattern. In this paper we present a case of proximal-type epithelioid sarcoma with an aggressive clinical course, including distant metastasis and death nine months after diagnosis.

Epidermotropic metastatic epithelioid sarcoma: a potential diagnostic pitfall

Epithelioid sarcoma (ES) represents an aggressive soft tissue tumor with varied morphologic and histopathologic presentations that typically elicits a broad differential diagnosis, including granuloma annulare, necrobiotic granuloma, fibrous histiocytoma, synovial sarcoma, amelanotic melanoma and poorly differentiated primary cutaneous and metastatic adenocarcinoma. ES is characterized microscopically by a nodular arrangement of abundant, deeply eosinophilic, polygonal tumor cells with frequent central necrosis and hemorrhage, rare mitotic figures and minimal pleomorphism. At the periphery, tumor cells are spindle shaped and may exhibit frequent local infiltration along tendons, fascial planes and neurovascular bundles. Immunohistochemistry typically reveals expression of both epithelial and mesenchymal antigens, such as cytokeratin and vimentin, respectively. The absence of a connection between tumor cells and the overlying epidermis, with or without an in situ carcinoma component, typically rules out a primary cutaneous squamous cell carcinoma. We report a case of stage IV proximal-type ES that mimicked molluscum contagiosum clinically and was histopathologically reminiscent of invasive squamous cell carcinoma because of attachment and colonization of the overlying epidermis. The case represents an unusual pathologic presentation of ES and highlights potential pitfalls in establishing the diagnosis.

Epithelioid sarcoma of the spine: case report and literature review

Epithelioid sarcomas are rare mesenchymal neoplasms mainly arising in the limbs of young adults. We report the case of a 24-year-old male presenting low back pain radiating to both lower limbs, constipation and urinary retention. The MRI scan showed an intraspinal lesion extending from L4 to S2. Surgery resulted in gross total removal of the extradural lesion and partial removal of the intradural component. The immunohistological study of the lesion was consistent with an epithelioid sarcoma. The patient was submitted to radiotherapy and chemotherapy, but a local recurrence of the lesion and dissemination along the neuraxis were observed 3 months after surgery. Despite treatment, the patient died 4 months after the surgical procedure due to multiorgan failure. Despite there being isolated reports of epithelioid sarcomas appearing in the spine, this is, to our knowledge, the first case with intradural extension.

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.

Dilemmas in the management of patients with vulval epithelioid sarcoma: a literature review

Vulval sarcomas are an extremely rare type of soft tissue tumor, the principal properties of which are unpredictable symptoms and frequent recurrences. This review discusses the management options specific for cases of vulval epithelioid sarcoma. The PubMed, Scopus and Cochrane databases were systematically searched and 28 studies met the inclusion criteria for our narrative review. The mean age of the 31 included patients was 31 years (range: 17-84). Local excision (19 out of 31, 61.3%), radical vulvectomy (8 out of 31, 25.8%) and hemivulvectomy (4 out of 31, 12.9%) were the principal surgical treatments. Radiotherapy and chemotherapy were performed in 8 and 5 patients, respectively. Recurrence of the disease was present in 13 out of 31 (42%). The interval to recurrence ranged from 1 to 48 months. The main location of recurrences was the local tissues, the lymph nodes and the lung. The mean period of follow-up was 38.5 months (range: 2-146 months). Cure was considered to have taken place in 19 out of 31 (61.3%) patients; 10 out of 31 (32.6%) died, and 2 out of 31 (6.4%) at the end of follow-up were alive but not considered cured. The first and principal step for the proper treatment of vulval epithelioid sarcomas is awareness of their existence by the specialist involved. Extensive imaging is proposed for staging, while the creation of a national or international register of patients with this malignancy would enable a more consistent approach to its management.

Superficial CD34-positive fibroblastic tumor: report of 18 cases of a distinctive low-grade mesenchymal neoplasm of intermediate (borderline) malignancy

Fibroblastic mesenchymal tumors show a spectrum of biological behavior, from benign to fully malignant. We report our experience of two decades with a distinctive, previously undescribed low-grade fibroblastic tumor of the superficial soft tissues. Eighteen cases were identified within our consultation files, previously coded as 'low-grade sarcoma, not further classified' and 'malignant fibrous histiocytoma, low grade'. The tumors occurred in adults (median age 38 years, range 20-76 years) of either sex (10 males and 8 females), ranged in size from 1.5 to 10 cm (mean 4.1 cm), and were confined to the superficial soft tissues of the thigh (N=5), knee (N=2), and other sites. Histological features included a fascicular growth pattern of the neoplastic spindled cells with striking, often bizarre cellular pleomorphism and variably prominent nucleoli. Necrosis was seen in one case. All cases showed strong, diffuse CD34 positivity and 68% of tested cases demonstrated focal cytokeratin expression. Desmin, ERG, FLI-1, smooth muscle actin, and S100 protein were negative. TP53 overexpression was absent. Fluorescence in-situ hybridization studies for TGFBR3 and/or MGEA5 rearrangements were negative in all tested cases. Clinical follow-up was available in 13 patients (median duration of 24 months; range 1-104 months). Twelve of 13 patients had no disease recurrence. One patient had regional lymph node metastases, 7 years after incomplete excision of the primary tumor. All patients are currently alive and disease free. The unique clinicopathological features of superficial CD34-positive fibroblastic tumor define them as a novel subset of low-grade fibroblastic neoplasms, best considered to be of borderline malignancy.

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.

Soft tissue sarcomas--new approaches to diagnosis and classification

The study of sarcoma pathology is a rapidly evolving field. The continued refinement of classic diagnostic techniques in conjunction with the molecular diagnostics has resulted in an abundance of data regarding this diverse and rare group of tumors. We anticipate that cutting edge technology including next generation sequencing will continue to further our understanding of saromagenesis and enable more precise classification and diagnosis of sarcomas in the future.

[Reconstruction of the thumb for an epithelioid sarcoma using a kite flap. A case report]

Epithelioid sarcoma is a rare lesion usually involving extremities. We report the case of a patient presenting with an epithelioid sarcoma of the dorsal aspect of the thumb. Surgical treatment consisted in a wide resection, arthrodesis of the metacarpophalangeal joint of the thumb and skin coverage with a kite flap. This case report illustrates a rare diagnosis potentially encountered by hand surgeons and the possible use of a kite flap in a non-traumatic context.

A novel angiomatoid epithelioid sarcoma cell line, Asra-EPS, forming tumors with large cysts containing hemorrhagic fluid in vivo

BACKGROUND

Whereas we can use several human epithelioid sarcoma (ES) cell lines for basic and preclinical research, an angiomatoid ES cell line has not been reported to date. We have treated a case of an angiomatoid ES developing in the right upper extremity of a 67-year-old man.

METHODS

An angiomatoid ES cell line, Asra-EPS was newly established and characterized for its morphology, growth rate and chromosomal analysis. Tumorigenicity of Asra-EPS cells was also analyzed in athymic nude mice.

RESULTS

Asra-EPS cells were round, polygonal or spindle-shaped with an abundant cytoplasm and have been maintained continuously in vitro for over 150 passages during more than 15 months. These cells secreted cancer antigen 125 (CA 125), interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) into the culture medium. Asra-EPS cells were tumorigenic when implanted in nude mice with tumors reaching a volume of 1000 mm3 at around 50 days. Histological features of tumors formed in mice were essentially the same as those of the original tumor, exhibiting a multinodular proliferation of eosinophilic epithelioid and spindle-shaped cells with prominent areas of hemorrhage and blood-filled cystic spaces strikingly corresponding to the potential of hemorrhagic cyst formation in the original tumor. They showed immunopositive staining for cytokeratins (AE1/AE3 and CAM5.2), epithelial membrane antigen (EMA), vimentin, CD31, CD34 and CA 125, but negative for integrase interactor 1 (INI-1) and factor VIII-related antigen.

CONCLUSIONS

The established cell line represents a biologically relevant new tool to investigate the molecular pathology of human angiomatoid ES and to evaluate the efficacy of novel therapeutics both in vitro and in vivo.