Nevus Sebaceous

Nevus sebaceous, a hamartoma of the skin and its adnexa, is characterized by epidermal, follicular, sebaceous, and apocrine gland abnormalities. Nevus sebaceous occurs in approximately 0.3% of all newborns. Both sexes are equally affected. The early infantile stage is characterized by papillomatous epithelial hyperplasia. The hair follicles are underdeveloped and the sebaceous glands are not prominent. During puberty, sebaceous glands become numerous and hyperplastic, apocrine glands become hyperplastic and cystic, and the epidermis becomes verrucous. The hair follicles remain small and primordial and may disappear altogether. During adulthood, epidermal hyperplasia, large sebaceous glands, and ectopic apocrine glands are characteristic histological findings. At birth, nevus sebaceous typically presents as a solitary, wellcircumscribed, smooth to velvety, yellow to orange, round or oval, minimally raised plaque. The scalp and face are sites of predilection. Lesions on the scalp are typically hairless. At or just before puberty, the lesion grows more rapidly, becomes more thickened and protuberant, and at times acquires a verrucous or even a nodular appearance. Nevus sebaceous may be complicated by the development of benign and malignant nevoid tumors in the original nevus. Neoplasms occur mostly in the fourth decade of life in approximately 10 to 30% of lesions. The majority of these tumors are benign; less than 1% of nevus sebaceous is complicated by malignant tumors. Because of the potential of malignant transformation, prophylactic full–thickness, complete excision of the lesion with 2 to 3 mm margins or ongoing observation is recommended.