Perforating pilomatricoma.

A case of "perforating pilomatricoma" is reported. A cutaneous horn-like tumor, the size of a grain of rice, developed on the left upper arm of a 51-year-old man. Histological examination revealed typical microscopic features of pilomatricoma. In addition, however, an interesting phenomenon was observed: a small portion of the mass had extruded from the upper dermis to the skin surface through the perforated epidermal channel. It might have been possible in this case for all of the tumor mass to be extruded by transepithelial elimination.