Epithelioid sarcoma resembling benign fibrous histiocytoma.

Epithelioid sarcoma (ES) is a rare malignancy notorious for its tendency to histologically mimic granuloma annulare and other palisading granulomatous processes. We report a case of ES on the right hand of a 23-year-old man that histopathologically resembled a benign fibrous histiocytoma. Superficial portions of the tumor were well differentiated, exhibiting spindled and ovoid cells with scant cytoplasm that surrounded sclerotic collagen bundles. More obvious atypia including greater cellularity, nuclear pleomorphism, and mitotic activity were mostly confined to the deep-seated regions of the tumor. In addition to palisading granulomatous processes, ES can mimic benign fibrous histiocytoma, and the superficial portions of ES may appear deceptively benign.