Trichoepithelioma: A small benign tumor derived from basal cells in the hair follicle. Trichoepithelioma may occur sporadically or as the cardinal feature of a uncommon genetic disorder called multiple familial trichoepithelioma characterized by the presence of many small tumors predominantly on the face, inherited in an autosomal dominant pattern. A trichoepithelioma can undergo malignant transformation into a basal cell carcinoma.
