Nevus Lipomatosus Superficialis
Nevus lipomatosus superficialis is a not-uncommon benign skin growth that is considered to be a hamartomatous proliferation of adipose tissue located in the dermis. It was originally named nevus lipomatosus cutaneous superficialis of Hoffman-Zurhelle. There are no known systemic associations with this benign skin growth, and no inheritance pattern has been described.
Clinical Findings: These nevi are most commonly found along the pelvic girdle. They have no sex or race predilection. They may occur at any age but are most common before the third decade of life. The lesions usually have a soft, bag-like appearance, often mimicking a large skin tag, and are flesh colored to yellow-tan. They are soft, nontender, easily moveable papules with a sessile base or pedunculated plaques with a thick stalk-like projection. The main differential diagnosis includes a skin tag, a compound nevus, and a connective tissue nevus. However, these lesions are much larger on average than the common skin tag.
Although the diagnosis can be considered clinically, the definitive diagnosis can be ascertained only after pathological evaluation. These lesions are often solitary, but reports of multiple lesions have been described in the literature. In the case of multiple tumors, the lesions are typically described as flesh-colored to slightly red dermal nodules that tend to coalesce into larger plaques. Some of the tumors have a cerebriform appearance to their surface. They can become very large (>10 cm in diameter) if left untreated. However, most never grow larger than 1 to 2 cm in diameter. A generalized variety of this condition has been described, but it is exceedingly uncharacteristic.
Children present after their parents notice the growth or growths, and a skin biopsy is often used to determine the diagnosis. Adults often present because of a slowly enlarging plaque that has an unsightly appearance or has become eroded or ulcerated due to trauma from the size of the lesion.
Pathogenesis: This condition is believed to be a hamartomatous process of adipose tissue located in the dermis. For some unknown reason, this normal-appearing adipose tissue proliferates within the dermis, often causing an outward herniation of the overlying epidermis, which ultimately leads to the distinctive clinical findings. The exact mechanism has not been elucidated. No genetic abnormalities of the adipose tissue have been established, and there is no known malignant potential.
Histology: Nevus lipomatosus superficialis has a characteristic pathology. It shows mature normal adipose tissue within the dermis. The one key finding is lack of connection of the abnormally located dermal adipose tissue with the normally located subcutaneous adipose tissue. Variable amounts of fat tissue make up the individual lesions. No definitive percentage has been established to make the diagnosis, but as little as 10% to more than 50% of each lesion is made up of adipose tissue. The overlying epidermis can be normal or can exhibit acanthosis and papillomatosis. The more cerebriform appearing the lesion is clinically, the more likely it is that epidermal changes will be seen on pathological examination. Skin tags do not have adipose tissue present, and this is a key discrimi- nating factor.
Treatment: These solitary lesions are best excised surgically; this gives the best cosmetic result and the best cure rate. Multiple lesions can be left alone after a diag- nosis is made. If the group of lesions is amenable to surgical excision without the potential for disfiguring scarring, or if the scarring would result in a better cosmetic outcome, surgical excision can be undertaken.