Desmoplastic trichilemmoma arising in a nevus sebaceous: a case report.

Nevus sebaceous is a congenital hamartoma of cutaneous structures, commonly associated with the development of secondary neoplasms. Desmoplastic trichilemmoma is characterized by the typical features of trichilemmoma (proliferation of columnar clear cells surrounded by cells forming a palisade resting on a thickened eosinophilic basement membrane) but contains a fibrous stroma with bands of epithelial cells, generally in the central zone. To the best of our knowledge, only 5 cases of desmoplastic trichilemmoma arising in a nevus sebaceous have been reported previously. Herein we report an unusual case of desmoplastic trichilemmoma arising in a nevus sebaceous and review the literature.