Primary epithelioid sarcoma of the kidney and adrenal gland: report of 2 cases with immunohistochemical and molecular cytogenetic studies.

Epithelioid sarcoma (ES) is a malignant mesenchymal neoplasm with some morphologic or immunophenotypic evidence of epithelial differentiation. The "classic" subtype occurs in younger patients, often in distal extremities as compared with the "proximal" type. Tumors of the proximal type primarily arising in solid organs are rare with only few case reports in the literature. We report 2 cases of primary ES in the kidney of a 27-year-old woman and the adrenal gland of a 73-year-old man. Clinical examination and imaging, including computed tomography and positron-emission tomography, did not reveal tumor elsewhere in both cases. Histologic features were those of ES, proximal type with epithelioid/rhabdoid phenotype. Immunohistochemical study in both cases showed strong, diffuse expression of epithelial markers, CD34, and CD31. Nuclear expression of SMARCB1 protein was lost, but fluorescence in situ hybridization analysis was negative for SMARCB1 deletion. We believe that these are the first reports of primary kidney and adrenal gland ES.