Trichilemmal carcinoma: review of 8 cases.

Clinical and histological data from 8 trichilemmal carcinomas are reviewed. The tumors occurred mainly on sun-exposed skin of the face of elderly people as small solitary, frequently ulcerated nodules. Histologically, they consisted of multilobulate, infiltrative growths, connected to the epidermis and pilosebaceous structures and showing features reminiscent of the outer root sheath of the hair follicle. The presence of lobules of clear, glycogen-rich cells with peripheral palisading, hyaline basement membranes, trichilemmal keratinization, and abortive follicular sheaths and the absence of ductal or acinar differentiation allow distinction from other clear cell tumors of the skin. Although the histological picture suggests a high-grade malignant neoplasm, trichilemmal carcinoma has an indolent course. No recurrence or metastases have been observed.