Answers to Self-Assessment examination of the American Academy of Dermatology

Abstract

DISCUSSION OF QUESTIONS 1-6 Nevus lipomatosus superficialis (NLS) is a rare benign lesion characterized by skin-colored or yellowish single or multiple soft papules or nodules with a smooth or wrinkled surface. Two clinical types have been described. The solitary nodular lesion of NLS resembles a skin tag with fatty herniation and appears in adulthood, most frequently on the knees, arms, axillae, ears, and scalp. The multiple lesions of NLS are characteristically distributed in a linear array, most commonly on the hip or buttock, and usually do not cross the midline. Other reported locations include the abdomen or thorax and, rarely, the face. The multiple lesions are usually present at birth or may arise in infancy, but have also been reported to appear later in life, as late as the third to sixth decade. There is no sex predilection or familial incidence. Histopathologic examination reveals groups and strands of fat cells embedded among the collagen bundles of the dermis, comprising 10% to 50% of the dermis. The dermis may be entirely normal, but may also show an increased number of fibroblasts, increased vascularity, and increased density of the collagen bundles. The fat cells are usually all mature, but occasionally incompletely lipidized cells may be observed. The ectopic fat cells are thought to be derived from perivascular mesenchymal tissue. The main histologic differential diagnosis is focal dermal hypoplasia, which differs from nevus lipomatosus superficialis in that there is extreme attenuation of the collagen in the former. The clinical differential diagnosis includes connective tissue nevus, focal dermal hypoplasia, lipoma, epidermal nevus, juvenile elastosis, lipoblastomatosis, and Michelin tire syndrome. The treatment of choice for NLS is surgical excision because the single and multiple variants of NLS persist throughout life. This patient was treated with carbon dioxide laser vaporization with good results. No malignant transformation within NLS has been reported.