Lipomatous metaplasia of superficial dermis.

Lipomatous metaplasia is an uncommon phenomenon. After identifying the presence of a band of adipocytes in the superficial reticular dermis underlying two excisions for basal cell carcinoma, we prospectively reviewed all skin specimens accessioned in our laboratory over a 6-month period and identified eight additional cases. In each example there was a band of adipocytes in the upper dermis, at the level of solar elastosis that was widely separated from the subcutaneous fat by a normal appearing reticular dermis. The cells were positive for S100 and negative for CD163. No connection between the superficial band of adipocytes and the subcutaneous or periappendageal fat was seen. The alterations were flat in configuration without polypoid changes. Eyerich et al. reported lipomatous metaplasia in the dermis of a patient with acute generalized exanthematic pustulosis and psoriasis, and postulated this to be a postinflammatory phenomenon. Fatty metaplasia occurs within a variety of cutaneous neoplasms including nevi, adnexal tumors and peripheral nerve sheath tumors. However, superficial dermal fatty metaplasia beneath cutaneous neoplasms is a newly described phenomenon and we suspect this process represents fatty metaplasia within solar elastosis and that it may occur more frequently than recognized.