This congenital lesion is composed of hamartomatous sebaceous glands and abortive hair follicles. It usually presents at birth as a yellow nodule or pebbled, hairless plaque on the scalp, forehead, or neck. Figure 22-1 shows the color and shape of the congenital lesion. With the loss of the effect of maternal hormones during the first few months of life, the lesion may quickly flatten and lose its distinctive color. During puberty, the nevus sebaceus again becomes raised, yellow, and verrucous. After this change, and usually during adulthood, nevus sebaceus may give rise to a wide variety of benign and malignant neoplasms. These include basal cell hamartomas, keratoacanthomas, syringocystadenoma papilliferum, basal cell epitheliomas, and, rarely, squamous cell carcinomas.