Nevus sebaceus, also known as organoid nevus or nevus sebaceus of Jadasshon, is a benign tumor that manifests in infancy or early childhood. This tumor has a risk of malignant transformation after puberty, and basal cell carcinoma is the malignant tumor that most frequently develops within these lesions.
Clinical Findings: Most of these growths are very small, and some escape detection for years. Others can be obvious at birth. They show a large range in dimensions. Most are solitary. The most common location in which to find a nevus sebaceus is within the scalp. Together, the scalp and face are overwhelmingly the areas of involvement, and it is rare to find a lesion any other place on the body. At or soon after birth, an area of the scalp is seen to be obviously affected. Nevus sebaceus typically start off as a thin, yellowish-brown patch or plaque. The area is almost universally devoid of terminal hair shafts. With time, the area becomes more cobblestoned in appearance. These nevi are usually asymptomatic but can be a cosmetic problem depending on their size and exact location. They occur in males and females with equal frequency. The lesions enlarge in proportion to the growing child. Before puberty, the risk of malignant transformation is very low. After puberty, approximately one third of these lesions develop a secondary growth, which usually manifests as a new nodule within the nevus sebaceus. The nodule can vary in color, but a light, translucent purple color is not infrequently seen. It is also common for a bleeding nodule or papule to develop within the underlying nevus sebaceus.
Most commonly, these growths that occur within the nevus sebaceus are benign in nature. The syringocystadenoma papilliferum is the most common benign tumor to develop within a nevus sebaceus. Because of the connection to the epidermis, these growths usually manifest as a draining or bleeding nodule that is slowly enlarging. The most common malignant growth to develop in a nevus sebaceus is a basal cell carcinoma. These usually manifest as a pearl-colored papule with a central ulceration and varying amounts of bleeding or crusting. The transformation to malignancy has been shown to increase with the age of the patient. It is estimated that about 1% of nevus sebaceus lesions will develop a malignant growth over the patient’s lifetime. There have been multiple reports of various tumors arising within a nevus sebaceus, and there have also been reports of multiple tumors arising within the same nevus sebaceus.
The nevus sebaceus syndrome is a very rare finding. It is similar in nature to the epidermal nevus syndrome. This syndrome can have a varying phenotype. The neurological system, including the eye, and the musculoskeletal, cardiovascular, and genitourinary systems can all be involved to varying degrees. Patients with this syndrome usually have abnormally large areas of cutaneous involvement. The lesions can be found anywhere on the body and are often multiple.
Pathogenesis: Nevus sebaceus is considered to be a hamartomatous process of the epidermis and adnexal structures of the skin. The exact mechanism and cause have not been discovered.
Histology: The histological picture is dependent on the age of the patient. Before puberty, the findings are more subtle than after puberty. Prepubertal lesions most commonly show undeveloped adnexal structures. After puberty, the lack of terminal hair follicles is a universal finding. Fine vellus hair follicles are often present but in reduced numbers. Prominent sebaceous glands are seen. Many of the sebaceous glands empty directly onto the surface of the epidermis. The overlying epidermis shows acanthosis and papillomatosis. The presence of apocrine glands is often appreciated.
Treatment: If treatment is undertaken, complete surgical excision is the treatment of choice. This not only removes the lesion but also removes the risk of malignant potential. Another approach is to watch and wait, with routine observation. If the nevus sebaceus develops any areas of change, a prompt biopsy is warranted. The timing of the surgical removal is controversial, and because the risk of malignancy is low, it is acceptable to wait until the patient is old enough to make the decision. The size and location of the nevus sebaceus dictates the type of surgical excision and repair required. Treatment of the rare nevus sebaceu syndrome requires a multidisciplinary team approach.