Selected topics in the pathology of epithelioid soft tissue tumors

Abstract

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.

Mammalian SWI/SNF complexes in cancer: emerging therapeutic opportunities

“…myoepithelial carcinomas, sinonasal basaloid carcinoma), schwannomas, and very rare cases of multiple meningiomas [61–65]. Whether the loss of SMARCB1 is universally concomitant with elevated expression of EZH2 in every SMARCB1-deficient neoplasm remains to be determined as new studies emerge.…”

Differential SALL4 immunoexpression in malignant rhabdoid tumours and epithelioid sarcomas

“…Histologically, a multinodular growth pattern and pleomorphic nuclei are more commonly associated with ESs, whereas cells with relatively uniform nuclei often grow in a diffuse sheet in MRTs . Although both tumour types can express epithelial markers, cytokeratin expression tends to be more limited in MRTs than in ESs . Therefore, in most classic cases, the distinction between these two entities poses little challenge.…”

Diagnostically Challenging Epithelioid Soft Tissue Tumors

“…As well, MPNST does not feature neoplastic giant cells, generally shows focal rather than diffuse expression of S100 protein, does not express other melanocytic markers, and lacks the cytogenetic aberrations of CCS. 13 Leiomyosarcoma typically shows increased eosinophilic cytoplasm and smooth muscle marker immunoreactivity, whereas CCS does not. Monophasic synovial sarcoma lacks the characteristic clear cytoplasm seen in CCS, and shows immunoreactivity to cytokeratins and EMA.…”

“…Additionally, the presence of tumor cell necrosis rather than necrobiosis is a helpful feature. 13 Other epithelioid mesenchymal malignancies demonstrate histologic overlap with ES, although most are readily distinguished based on a combination of histopathologic appearance and immunohistochemical markers. These include epithelioid MPNST, epithelioid angiosarcoma, ES-like hemangioendothelioma, and MERT.…”

“…15 MERT shares many features with proximal-type ES, including rhabdoid tumor cell morphology, cytokeratin expression, and loss of INI1 immunoreactivity. 13 However, MERT occurs primarily in children, with a wide range of anatomic sites, and uniform CD34 negativity. In fact, most diagnoses of MERT made in adults more likely represent other tumors with rhabdoid-type morphology.…”