What exactly is trichoepithelioma?

Skin neoplasm: Trichoepithelioma is a benign adnexal skin neoplasm It is derived from basal cells in the hair follicle and frequently presents as a basal cell Ca.. It 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. At times the trichoepithelioma can undergo malignant transformation into a basal cell carcinoma. The gene involved in the familial form of trichoepithelioma is located on band 9p21.