Solitary epithelioid histiocytoma (reticulohistiocytoma) of the glans penis.

Solitary epithelioid histiocytoma (previously called reticulohistiocytoma) is a rare benign dermal histiocytic proliferation characterized by the presence of large, eosinophilic histiocytes with 'glassy' cytoplasm. This entity assumes importance because of its close histologic resemblance to several benign as well as malignant cutaneous lesions. Involvement of the penis is extremely rare, and to our knowledge, only one case has been previously described in the literature. We report a case of solitary epithelioid histiocytoma in a 34-year-old man who presented with a nodule in the glans penis. Microscopy showed proliferation of large epithelioid histiocytes with abundant eosinophilic cytoplasm, which expressed CD68, CD163 and vimentin. This case highlights the significance of recognizing this unusual lesion and differentiating it from its histologic mimics.