Nevus Sebaceous

Nevus sebaceous (NS) is a common congenital hamartoma (benign tumor) composed of malformed sebaceous glands (large and not associated with follicular units), apocrine glands, and follicular units that typically present on the scalp.

NS represents at defect in cutaneous embryologic development; its exact etiology is unknown.
NS occurs sporadically.

NS can occur anywhere on the body, but >97% of lesions occur on the head or neck, most often on the scalp.
NS initially presents as a solitary, well-circumscribed, oval or linear, hairless, pink or yellow-orange/tan, finely papulated plaque (Fig. 1.5).
Occasionally, NS can be thicker or have papillomatous projections, simulating a wart; or present as a large pedunculated lesion at birth (Fig. 1.6).
After infancy, lesions flatten and grow proportionately with child.
At puberty, under the influence of androgens, NS thicken, become darker yellow or brown, more papular or verrucous, and can be friable or pruritic (Fig. 1.7).
Warty growths, representing secondary adnexal neoplasms, may develop within an NS during adolescence or later.

Diagnosis is clinical.
Dermatoscopy showing bright yellow dots, and an absence of hair follicles can help make the definitive diagnosis, before the characteristic features become apparent.

* This consists of a hand-held magnifier that allows inspection of skin lesions unobstructed by skin surface reflections.

Differential Diagnosis

Aplasia Cutis Congenita

Congenital Triangular Alopecia (see Chapter 9: Hair and Nail Disorders)

Skin-colored, flat, lancet-shaped, alopecic patch that remains stable over time.

Other Congenital Hamartomas (i.e., Epidermal Nevus)

Management

A complete physical examination should be performed to rule out other congenital defects and determine extent of NS.
Complete surgical removal remains the treatment of choice for NS given the concern for warty proliferation, permanent alopecia, and the development of secondary tumors at puberty.
More recent investigations have shown that the risk of developing a malignant neoplasm within an NS is quite low.
Recommendations for timing of excision vary. Advantages of removing the lesions in infancy are greater laxity of tissues, smaller size of lesion, and removal of any cosmetic impact on a developing child; the main disadvantage to early removal is the need for general anesthesia.
Most often, a NS is removed in late childhood, prior to the onset of puberty, when the patient is able to cooperate with excision under local anesthesia and the lesion has not yet thickened under the influence of androgens.
In cases of an extensive or widespread NS, a thorough medical history and physical examination should be performed with special attention to the ocular, neurologic, and musculoskeletal systems. Radiologic evaluation and further workup should be symptom-directed.
Various ablative treatments including cryotherapy and electrodessication have been used to treat NS, but these do not remove risk of neoplasia and can still leave areas of alopecia.