Amelanotic Malignant Melanoma of the Male Urethra: A Potential Diagnostic Pitfall.

A rare disease in an unusual site can closely mimic a typical presentation of a common disease, sometimes with devastating consequences. We present a case of primary amelanotic malignant melanoma of the urethra in a male, with clinical and histological characteristics that could have led to a mistaken diagnosis of high-grade urothelial carcinoma. Amelanotic mucosal melanoma should be suspected in all cases of high-grade mucosal tumors with practically any appearance (epithelioid, sarcomatoid, anaplastic, mixed). Morphological hints pointing toward melanoma-such as the presence of sparse melanin pigment or melanoma in situ-should be sought, and if absent, an immunohistochemical panel comprising S100 and HMB45 should be performed.