Pigmented sweat gland tumor mimicking melanoma.

Eccrine poroma, a common adnexal neoplasm, usually presents as a solitary, smooth, flesh-colored nodule on the foot or hand. Eccrine porocarcinoma is extremely rare and much more variable in its morphology and location. Both tumors can contain melanocytes and melanin. We describe a patient with an enlarging, eroded brownish black nodule on his shoulder. Examination of a biopsy specimen showed it to be derived from acrosyringium and to contain abundant melanin and scattered dendritic melanocytes. Eccrine poroma and porocarcinoma should be considered in the clinical differential diagnosis of pigmented tumors.