In five benign nodular sweat gland tumors, areas of melanin pigmentation were found within the tumor parenchyma. Active melanogenesis was confirmed by the presence of 3,4 dihydroxyphenylalanine (DOPA) positive cells within two of the tumors, and details of other standard enzyme histochemical reactions are described. Pigmentation was extensive in one tumor and occurred in the greater part of the lesion. In the other tumors, the melanocytic activity was confined to relatively small areas in the upper parts of the lesions only. The significance of these findings in relationship to the histogenesis of sweat gland tumors is briefly discussed.
Wilson-Jones E. Pigmented Nodular Hidradenoma. Arch Dermatol. 1971;104(2):117-123. doi:10.1001/archderm.1971.04000200005002