A nevus sebaceous is an unusual lesion or patch of hairless skin that most commonly appears on the scalp or face. In most cases, lesions are benign and do not cause health problems, though there is a very small chance that a nevus can become cancerous late in life. Patches are typically noticed at birth or in early childhood and tend to be soft, smooth, and more orange or yellow than surrounding skin. By puberty, they may become bumpy or rough to the touch. Treatment in the form of excision surgery is only needed if a nevus sebaceous turns malignant or becomes a major aesthetic concern for a patient.

It is thought that a nevus sebaceous arises during prenatal development as the outer layers of skin are first formed. Research suggests that a minor genetic defect is responsible for abnormalities in the formation of sebaceous glands within the skin of the scalp and face. At birth, a lesion typically appears as a round, slightly raised bald patch that is velvety to the touch. There may be only a single lesion or a close cluster of raised patches surrounded by normal hair.

Hormonal changes at the time of puberty can cause a nevus sebaceous to grow larger and develop a wart-like appearance. A lesion typically has an orange, brown, or yellow tint. If the condition is left untreated, there is very small risk of a nevus sebaceous becoming malignant. A hard, rough tumor can develop and potentially grow very large on the head. It is unlikely for the cancer to spread quickly to other areas of skin or elsewhere in the body, however.

Doctors often notice nevus sebaceous symptoms shortly after an infant is born. Very small lesions may go unnoticed until later in childhood or occasionally after puberty when the patches start to change in appearance. Skin biopsies are usually collected and analyzed to confirm a nevus sebaceous and to make sure the lesion is not cancerous. After diagnosing the condition, the doctor can explain different treatment options.

Most patients with small, noncancerous lesions do not need aggressive treatment. Patches on the scalp can usually be concealed with a hat or by parting the hair a certain way. If a nevus sebaceous is malignant or causes appearance concerns, it can be cut out during a fairly simple outpatient surgical procedure. Photodynamic therapy, which involves eroding a lesion with a combination of acid and laser light, is a new and promising nonsurgical option for some patients.