Carcinomatous transformation in a pilomatrixoma.

A case of a pilomatrixoma with exceptional features in an 18-year-old man is described. The lesion presented itself as a mass in a supraclavicular fossa. Four attempts at extirpation by conservative local excisions were failures. It recurred each time but was finally ablated by a radically wide excision and closure by a deltopectoral flap. Histology of the surgical specimen revealed it to consist of hyperchromatic, vesicular basaloid cells, many in mitosis and infiltrating adjacent tissue or invading blood vessels. The authors believe that these features qualify the lesion as a carcinomatous.