Nevus sebaceous is a lesion of the epidermis (upper layers of the skin), sebaceous glands, hair follicles, apocrine glands and connective tissue.  They appear as a yellow-orange plaque-like lesion at birth.  They are typically located in the scalp or on the head and neck.  During puberty they often change in color and shape.  Later in life, basal cell and squamous cell cancers may arise in the nevi sebaceous.  Resection of this lesion is recommended before puberty.