A nevus sebaceus is a solitary, well-circumscribed, yellow-orange hairless plaque located on the face or scalp that is a hamartoma of follicular, sebaceous, and apocrine origin.
SYNONYMS Nevus sebaceus of Jadassohn, organoid nevus.
AGE Usually present near birth. May appear in childhood or adulthood. Increase in prominence at onset of puberty.
GENETICS Usually sporadic, rare familial forms reported. Mutations in the HRAS and KRAS genes have been identified in sebaceus nevi.
A nevus sebaceus is typically present near birth and has two stages: a prepubertal/infantile stage (Fig. 10-1) and pubertal/adolescent phase (Fig. 10-2).
Nevus sebaceous, infant
A pebbly, hairless flesh-colored plaque on the scalp of an infant.
Nevus sebaceus, prepubertal child
An elevated orange, hairless plaque with pebbly surface in a prepubertal child.
TYPE Hairless plaque surface may be velvety, verrucous, or papillomatous.
COLOR Yellow, yellow-brown, orange, pink.
SIZE Few millimeters to several centimeters.
SHAPE Round, oval, or linear.
DISTRIBUTION Head and neck.
ARRANGEMENT Solitary lesion; rarely, multiple lesions have been reported.
Typically there are no systemic symptoms. In the scalp, the lesion remains hairless. Rarely, extensive lesions can be associated with ocular, CNS, or skeletal abnormalities. This constellation of extensive sebaceus nevi and associated abnormalities is termed nevus sebaceus syndrome (also known as Schimmelpenning syndrome). The association of nevus sebaceus, CNS malformations, aplasia cutis congenita, ocular limbal dermoid, and pigmented nevus has also been rarely reported and termed SCALP syndrome.
The differential diagnosis includes other appendageal tumors; smaller lesions can resemble warts. Juvenile xanthogranuloma is another benign proliferation with a yellowish-hue also presenting in infancy.
DERMATOPATHOLOGY Infancy: numerous immature sebaceous glands with irregular morphology and cords or buds of undifferentiated hair follicles. Adult: papillomatous hyperplasia of the epidermis with hyperkeratosis and hypergranulosis. There are also typically ectopic apocrine glands located deep in the dermis.
Nevus sebaceus tends to grow slowly and become thicker and more papillomatous with age. Approximately 10% may have benign or, rarely, malignant neoplastic changes that manifest as nodules or ulcers within the lesion: trichoblastoma, trichilemmoma, syringocystadenoma papilliferum (Fig. 10-3) are the most common neoplasms. Other possible growths include sebaceous adenoma, ...