Nevus Sebaceus Appearance
Nevus sebaceus is usually a solitary, yellowish to flesh-colored plaque and occurs most commonly on the scalp, forehead, or postauricular areas. It tends to be linear or oval shaped, measuring 1 to 3 cm in diameter.
The lesion evolves in three stages corresponding to sebaceous gland maturation through childhood, puberty, and adulthood.
In the first few months of life, the sebaceous glands are well developed as a result of maternal hormonal stimulation, although surrounding hair structures are incompletely differentiated.
In childhood, the lesion is a barely raised, pink to tan, velvety surfaced hairless plaque and is asymptomatic. The sebaceous glands are small in size and number; incompletely developed hair structures may be seen.
With puberty, hormonal influences bring about diagnostic changes. Sebaceous glands mature and increase in size and density. Hair structures remain undifferentiated, and papillomatous epidermal hyperplasia develops. Ectopic apocrine glands may also be found deep within the underlying dermis. The plaque tends to thicken, becomes larger and more verrucous, and has a yellow-white and pink speckled appearance. Lesions at this stage are easily traumatized and may be tender.
The third stage of evolution occurs during adulthood. Appendageal tumors may develop within nevus sebaceus. Each such tumor has its own histologic pattern. The most common tumor is a syringocystadenoma papilliferum, a benign apocrine tumor seen in up to 20% of lesions.
Basal cell carcinoma is the second most common tumor and most common malignancy that develops in nevus sebaceus. It occurs in roughly 7% of lesions.
A nevus sebaceus may be confused with linear epidermal nevus or other variants of nevi clinically.