To the Editor.—
The infiltration of mature fat cells among intradermal nevus cells in melanocytic nevi is a relatively common event and correlates with age.1 Nonetheless, the origin of these cells is uncertain. Various hypotheses for this fatty infiltration have included (1) presence of nevus lipomatosus in melanocytic nevi,1 (2) fatty metamorphosis of nevus cells,2,3 and (3) development of fat cells from mesenchymal elements.1 Since nevus lipomatosus is usually a congenital lesion and the age of patients with melanocytic nevi that contain fat is usually greater than 50 year s,1 the first explanation is unlikely. With regard to the second possibility, Maize and Foster2 could find no evidence histologically of transition from nevus cells to lipocytes, making this interpretation less credible.S100 protein is an acidic calcium-binding protein that is found in neuroepithelium. In the skin, this substance is found within melanocytes, Schwann's cells, Langerhans'
Barnhill RL, Penneys NS, Landau-Price D, Nadji M, Ziegels-Weissman J, Matsuo S. Fat Cells in Intradermal Nevus Do Not Contain S100 Protein. Arch Dermatol. 1985;121(2):169-170. doi:10.1001/archderm.1985.01660020027006