Squamomelanocytic tumor: an unusual and distinctive entity of uncertain biological potential

We report a case of a squamomelanocytic tumor of the skin. Clinically, the lesion was felt to be a melanocytic or vascular tumor but histologically was characterized by epithelioid cells with focal squamous differentiation. Immunohistochemical staining showed that half of cells stained with MNF116 and a smaller proportion stained with S100 and Melan A. A third population did not stain with either set of antigens. The lesion has some similarities to a melanocytic matricoma but no evidence of matrical differentiation. The biological potential of this distinctive tumor is not known because so few have been reported.