Trichoblastoma: management of a rare skin lesion.

A 15-year-old girl presented with a 2-year history of an enlarging parietal scalp lesion. Excisional biopsy revealed trichoblastoma, a benign secondary tumor arising from a nevus sebaceous. There is no consensus in the literature about the surgical management of nevus sebaceous in children owing to the low incidence of secondary malignancy. There is a 20% lifetime risk of transformation to a soft tissue neoplasm, most of which are benign; but malignant neoplasms have also been reported. At minimum, these lesions need to be followed clinically over the patient's lifetime if left in situ. Recurrence after excision is rare.