Primary Sclerosing Epithelioid Fibrosarcoma of the Kidney: A Case Report and Review of the Literature

Abstract Sclerosing epithelioid fibrosarcoma (SEF) is a rare fibrosarcoma variant that features rounded carcinoma-like epithelioid cells arranged into compact nests, cords, and single-cell patterns within a highly sclerotic stroma and has a consistent translocation (EWSR1-CREB3L1/2). To our knowledge, there are 110 cases of pure SEF reported, to date, with 15 occurring at intra-abdominal sites. Primary SEF of the kidney is exceptionally rare. We present a case of SEF that arose in the kidney. Histological examination revealed densely hyalinized epithelioid tumor suggestive of SEF. The diffuse immunohistochemical staining of MUC4 by neoplastic cells and the presence of EWSR1 gene rearrangement by fluorescence in situ hybridization analysis confirmed the histological diagnosis.