Trichilemmal carcinoma is a rare malignant neoplasm arising from the outer root sheath of the hair follicle, in the fourth and ninth decades of life, in sun-exposed skin. This tumor pressents as plaques, papules, or nodules, with or without ulceration, grow rapidly, and are locally aggressive.

Two cases of long-standing tumors are presented, one previously diagnosed as clear cell hidradenoma and the second with a history of multiple resections with continuous recurrence.

Histologically, tumors display polygonal clear cells (PAS positive, diastase sensitive), solid/lobular/trabecular infiltration, peripheral nuclear palisading, trichilemmal keratinization, high mitotic index and ulcerations. The cells are CK17, CD34and KRT15 positiv. The Immunohistochemistry is an important tool for differentiating it from other simulators.