Primary Epithelioid Sarcoma of Bone: Report of a Unique Case, With Immunohistochemical and Fluorescent In Situ Hybridization Confirmation of INI1 Deletion

A unique case of epithelioid sarcoma involving the mandibular alveolar mucosa

Epithelioid sarcoma (ES) is an infrequent, malignant, mesenchymal, soft-tissue neoplasm of uncertain histogenesis characterized by epithelioid cytomorphology. The lack of SMARCB1/INI1 (Integrase interactor 1) expression typifies this pathology. It usually presents as a painless, indolent, slowly enlarging lesion or rarely as an aggressive growth. Epithelioid sarcoma affects mostly pediatric patients or young adults. It recurs quite frequently and possesses a high degree of metastatic potential. Two predominant histomorphologic patterns include classic/conventional type and proximal types. Epithelioid sarcoma immunohistochemically shows vimentin, cytokeratin, epithelial membrane antigen, CD34 positivity, and negative staining with S100 and desmin. Management is generally multimodal, including wide surgical resection, radiotherapy, and chemotherapy. To date, to our knowledge, only 11 instances of head and neck ES have been reported in the literature. Our case deals with the diagnosis of intraoral ES in a 55-year-old female patient, probably the first one to involve the mandibular mucosa, based on relevant clinical-radiologic-pathologic-immunohistochemical findings.

Vascular Tumors of Bone: Updates and Diagnostic Pitfall

Vascular tumors of bone can be diagnostically challenging because of their rarity and histologic overlap with diverse mimics. Vascular tumors of bone can be categorized as benign (hemangioma), intermediate-locally aggressive (epithelioid hemangioma), intermediate-rarely metastasizing (pseudomyogenic hemangioendothelioma), and malignant (epithelioid hemangioendothelioma and angiosarcoma). Recurrent genetic alterations have been described, such as FOSB rearrangements in pseudomyogenic hemangioendothelioma and a subset of epithelioid hemangiomas; CAMTA1 or TFE3 rearrangements in epithelioid hemangioendothelioma. This review discusses the clinical, histologic, and molecular features of vascular tumors of bone, along with diagnostic pitfalls and strategies for avoidance.

SMARCB1/INI1-deficient tumors of adulthood

The SMARCB1/INI1 gene was first discovered in the mid-1990s, and since then it has been revealed that loss of function mutations in this gene result in aggressive rhabdoid tumors. Recently, the term "rhabdoid tumor" has become synonymous with decreased SMARCB1/INI1 expression. When genetic aberrations in the SMARCB1/INI1 gene occur, the result can cause complete loss of expression, decreased expression, and mosaic expression. Although SMARCB1/INI1-deficient tumors are predominantly sarcomas, this is a diverse group of tumors with mixed phenotypes, which can often make the diagnosis challenging. Prognosis for these aggressive tumors is often poor. Moreover, refractory and relapsing progressive disease is common. As a result, accurate and timely diagnosis is imperative. Despite the SMARCB1/INI1 gene itself and its implications in tumorigenesis being discovered over two decades ago, there is a paucity of rhabdoid tumor cases reported in the literature that detail SMARCB1/INI1 expression. Much work remains if we hope to provide additional therapeutic strategies for patients with aggressive SMARCB1/INI1-deficient tumors.

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.

Two Cases of Intraosseous Pseudomyogenic (Epithelioid Sarcoma-Like) Hemangioendothelioma With Unusual Features, Expanding the Clinicopathological Spectrum

Pseudomyogenic (epithelioid sarcoma-like) hemangioendothelioma (PMHE) is a distinct vascular neoplasm mostly observed in the lower extremities of young adults with characteristic histopathological features. In this article, we present 2 unusual cases of PMHE. Case 1: A 28-year-old male presented with pain and stiffness in his left shoulder. Radiologic examination revealed an expansile, lytic, heterogeneously enhancing, destructive lesion in his left scapula, along with multiple avid marrow lesions in his other bones. Biopsy revealed a cellular tumor composed of plump spindly and epithelioid cells arranged in fascicles and focally, in clusters, admixed with neutrophils and histiocytes, with interspersed many osteoclast-like giant cells and reactive bone. Case 2: A 63-year-old male presented pain and swelling in his right middle finger, with no other lesion elsewhere in his body. Radiologic imaging disclosed a 1.5-cm-sized lobulated, expansile, lytic, destructive lesion in the distal end of the third metacarpal bone of his right hand. Biopsy examination revealed a cellular spindle cell tumor, composed of plump spindly cells, arranged in fascicles, including "tadpole-like" or "strap-like" cells and interspersed inflammatory cells. Immunohistochemically, tumor cells in both cases were positive for AE1/AE3, CD31, and Fli1, while negative for desmin and CD34. INI11 was retained. The presented cases of PMHE, occurring at unusual locations, in an older individual in the second case, along with variable histopathological features, noted in the first case, seem to expand the clinicopathological spectrum of these uncommon neoplasms. Differential diagnoses and review of similar cases are presented.

Primary rhabdoid epithelioid sarcoma of the left thigh mimicking epithelioid rhabdomyosarcoma: A diagnostic pitfall

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The diagnosis of epithelioid sarcoma based on only the clinical manifestation has proven to be difficult.

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Thus, the histopathology examination followed by immunohistochemistry is considered as the main modality for the diagnosis.

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Better understanding of clinical properties of epithelioid sarcoma will aid in deciding the best treatment for the patient.

Introduction

Epithelioid sarcoma (ES) is a rare mesenchymal tumor, accounting for less than 1% of all adult soft-tissue sarcomas. The diagnosis of such malignancy is challenging. We reported a 31-year-old male diagnosed with rhabdoid ES that histologically mimicked epithelioid rhabdomyosarcoma in a 31-year-old male.

Case presentation

A 39-year-old male presented with pain in the left thigh. He had planned for open reduction internal fixation due to left femur fracture. During the surgery, the surgeon found abnormal appearance of the bone and the surrounding tissue. The histopathology examination showed spindle-to-polygonal epithelioid cells arranged in nodular pattern with necrotic areas. Immunohistochemistry examination revealed vimentin and CK positive expression, while myogenin was negative. Further immunostaining using CD34 and HMB45 were also negative.

Discussion

The diagnosis of ES based on only the clinical manifestation has proven to be difficult. Thus, the histopathology examination followed by immunohistochemistry is considered as the main modality for the diagnosis. Better understanding of clinical properties of ES will aid in deciding the best treatment for the patient.

Update on selected advances in the immunohistochemical and molecular genetic analysis of soft tissue tumors

Although traditional morphological evaluation remains the cornerstone for the diagnosis of soft tissue tumors, ancillary diagnostic modalities such as immunohistochemistry and molecular genetic analysis are of ever-increasing importance in this field. New insights into the molecular pathogenesis of soft tissue tumors, often obtained from high-throughput sequencing technologies, has enabled significant progress in the characterization and biologic stratification of mesenchymal neoplasms, expanding the spectrum of immunohistochemical tests (often aimed towards recently discovered genetic events) and molecular genetic assays (most often fluorescence in situ hybridization and reverse transcription-polymerase chain reaction). This review discusses selected novel molecular and immunohistochemical assays with diagnostic applicability in mesenchymal neoplasms, with emphasis on diagnosis, refinement of tumor classification, and treatment stratification.

Primary Epithelioid Sarcoma of the Zygomatic Bone

Primary epithelioid sarcoma (ES) of bone is extremely rare with only 2 reported cases in the English literature. A previously healthy 18-year-old man presented with a 6-month history of right facial numbness and tingling and right eye diplopia. A computerized tomography scan revealed an ill-defined mass with dense osseous matrix centered in the right zygomatic bone. An outside biopsy was read as osteosarcoma. The resection specimen revealed large epithelioid and spindle cells embedded in a prominent hyalinized matrix with focal metaplastic bone formation. The tumor cells were strongly and diffusely positive for AE1/AE3 and epithelial membrane antigen, but a definitive diagnosis of ES was not immediately reached due to the presence of dense hyalinized matrix and weak expression of SAT2B by tumor cells. Deficient INI1 protein expression by immunohistochemistry and homozygous loss of the SMARCB1 gene by chromosomal microarray analysis ultimately justified this tumor's designation as ES.

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.

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.

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.

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.

Loss of INI1 protein expression defines a subgroup of aggressive central nervous system primitive neuroectodermal tumors

Pediatric embryonal brain tumors can be difficult to classify. Atypical teratoid rhabdoid tumors (ATRT) contain rhabdoid cells, while primitive neuroectodermal tumors (PNETs) are composed of "small round blue cells." Loss of INI1 is a common event in ATRT; therefore, we investigated if the loss of INI1 protein expression was also observed in central nervous system (CNS) PNET and pineoblastoma. A histological review of 42 CNS PNETs and six pineoblastomas was performed. INI1 expression was assessed by immunohistochemistry. Sequencing was performed on the mutational hotspots of INI1. INI1-immunonegative tumors were further investigated using fluorescence in situ hybridization. Epithelial membrane antigen (EMA) protein expression was assessed in six CNS PNETs to further define the phenotype. Five CNS PNETs without rhabdoid cell morphology were immuno-negative for both INI1 and EMA. Of these primary CNS PNET patients, three died <11 months postdiagnosis, which was dissimilar to the INI1-immunopositive primary CNS PNETs where 18/24 (75%) patients were alive 1 year postdiagnosis. We have identified a small subgroup of CNS PNETs which lack INI1 protein expression, but have no evidence of rhabdoid cell morphology. INI1 protein loss may occur through mechanisms other than gene deletion. INI1 immunohistochemistry should be performed for all CNS PNET cases.

Prognostic determinants in epithelioid sarcoma

BACKGROUND

Epithelioid sarcoma (ES) is a rare soft tissue neoplasm that usually arises in the distal extremities of young adults, presents a high rate of recurrences and metastases and frequently poses diagnostic dilemmas. In order to identify markers useful for patient stratification purposes, we investigated the prognostic impact of clinical and molecular patient characteristics, including the status of SMARCB1 tumour suppressor gene, in a consecutive series of ES cases.

METHODS

Kaplan-Meier survival curves were compared by the log-rank test. Immunophenotyping and SMARCB1 protein expression were analysed by immunohistochemistry or western blotting in 40 ES patients for which tumour material was available. Cases lacking SMARCB1 protein expression were investigated for the presence of gene mutations and gene deletions by exon sequencing, fluorescent in situ hybridization and quantitative PCR.

RESULTS

FNCLCC tumour grade 3 and proximal-type histology significantly correlated with shorter overall survival (log-rank p=0.0046 and p=0.0001, respectively). We identified loss of SMARCB1 protein expression in the majority of ES cases (25/40, 62.5%), including 24/34 (71%) adult cases but only 1/6 (17%) paediatric/adolescent cases (p=0.02, two-tailed Fisher's exact test). The absence of protein is strongly correlated with SMARCB1 gene deletion (p=0.003, two-tailed Fisher's exact test). We observed a trend towards the correlation between SMARCB1 inactivation and both higher tumour grading and a clinical course of the disease characterised by the occurrence of multiple relapses/metastasis.

CONCLUSION

These data show that both tumour grading and subtype are prognostic factors in ES. Loss of SMARCB1 protein expression in ES is a frequent occurrence mediated by gene deletion events, thus pointing to a crucial role of SMARCB1 in ES genesis. Analysis of SMARCB1 status in ES warrants prospective investigation as a prognostic marker and therapeutic target.