Trichilemmoma: Analysis of 40 New Cases

Clinical and histopathologic features of 40 new examples of trichilemmoma were analyzed. Lesions were almost invariably solitary, asymptomatic, and located on the face. Two-thirds of the patients were men; median age was 59 years; median duration was a few months; and clinical impression was frequently basal cell carcinoma or verruca. Histopathologic examination frequently disclosed lobular acanthosis of glycogenrich clear cells oriented about a follicle. At the edge of the lesion, a palisade of columnar cells, that resembled the outer root sheath of a hair follicle, rested on a wellformed basement membrane. Trichilemmoma must be differentiated from other clear cell tumors of skin, including Degos acanthoma, clear cell hidradenoma, basal cell carcinoma, sebaceous neoplasms, other follicular tumors such as inverted follicular keratosis and tumor of follicular infundibulum, and metastatic renal carcinoma.