Naevus superficialis lipomatosus. A clinicopathological report of twenty cases.

Naevus superficialis lipomatosus (NSL) is a rare malformation consisting of multiple or solitary papules usually occurring on the lower trunk or gluteal regions. In this study the clinical features of twenty new cases are described with a detailed account of the histopathology. Notable were the marked variability in the amount of ectopic fat found in the lesions, and the presence of associated abnormalities of the connective tissue, the vessels, and the skin appendages. In early lesions, mononuclear cells differentiating into lipoblasts could be identified around proliferating capillaries. Two clinical types were distinguished. First, the classical type (7 cases) consisting of multiple lesions occurring in a zonal distribution, and secondly the solitary papule or nodule (13 cases). The latter type can be difficult to distinguish from a skin tag with fatty herniation.