A 54-year-old woman presented with a firm, exophytic cutaneous nodule on the thigh which had been present for 5 years. A punch biopsy was performed.

Pathologic Findings Present within the dermis there is a sheet-like proliferation of relatively plump and quite monomorphic epithelioid or more ovoid cells with palely eosinophilic cytoplasm and plump but uniform vesicular nuclei. There are numerous rounded stromal blood vessels, some of which show perivascular fibrosis. In areas, the cells appear to be arranged in whorls. A notable subset of the neoplastic cells is binucleate. There is no atypia or pleomorphism and there is no evident epidermal origin. Immunostains show that S-100 protein and HMB45 are negative but there is multifocal positivity for EMA and diffuse cytoplasmic positivity for ALK.

EPITHELIOID BENIGN FIBROUS HISTIOCYTOMA