Multiple hereditary trichoepitheliomas and basal cell carcinomas.

A 45-year-old man with multiple hereditary trichoepitheliomas developed 2 tumors which showed malignant behavior. These tumors contained some undifferentiated basal cell carcinoma-like areas, but also some regions with a high degree of follicular differentiation. In addition he had several small tumors with predominantly undifferentiated features interspersed with the trichoepitheliomas. The relationship between multiple hereditary trichoepitheliomas and basal cell carcinomas is reviewed.