A red papule with a yellowish hue

A 35-year-old man had an asymptomatic, 5 mm papule on his left shoulder which had persisted for six months. Close examination showed a sharply circumscribed, elevated red papule with a yellowish hue (Figure 1). No similar lesions were found on general examination of his skin. Excision biopsy showed an elevated epidermis under which there was a diffuse infiltrate of histiocytes (Figure 2). Many of the histiocytes were multinucleated and had a central wreath of nuclei with a foamy periphery (Touton giant cells). There was a background of lymphocytes, eosinophils and plasma cells between the histiocytes.