Trichilemmal carcinoma associated with xeroderma pigmentosa: report of a rare case.

Trichilemmal carcinoma is a rare malignant skin adnexal tumor derived from the outer root sheath epithelium of the hair follicle. We describe a rare case of trichilemmal carcinoma of the upper lip associated with xeroderma pigmentosa in a young patient. We demonstrate that this tumor, as well as the more frequently reported squamous cell carcinoma and basal cell carcinoma can occur in association with xeroderma pigmentosa. Making this diagnosis is imperative as the biological behavior of Trichilemmal carcinoma is less aggressive than that of other epithelial malignancies, requiring a different approach to treatment planning.