Cutaneous lymphoid hyperplasia on a preexistent melanocytic nevus.

Case Report An 83-year-old man had had a painful growth on his back for a month. He did not remember any trauma, insect bites or preexistent lesions at the site. His medical history was significant for type II diabetes, hypercholesterolemia, myocardial infarction and coronary bypass surgery. He had been taking gliclazide for 2 months, and sotalol, potassium, furosemide, aspirin and simvastatin for several years. Clinically, there was a 5-cm inflammatory, erythematous nodule on the back. The nodule was homogenous, and no pigmented lesion was noticed clinically. Incisional biopsy showed a normal epidermis, a dermal cell population made of small nests of pigmented cells, and a dense dermal infiltrate composed of small lymphocytes ( fig. 1 , 2 ). The pigmented cells were S-100 protein positive, and the lymphocytes were predominantly CD20-positive (B) cells. There were also a few small, CD3-positive lymphocytes at the periphery. The lymphocytic infiltrate did not dissociate nevus nests. The nevus had been completely excised with the biopsy. Borrelia burgdorferispecific antibodies were negative. Nevertheless, in the hypothesis of borrelial lymphocytoma, a 15-day course of doxycycline was prescribed. The remaining nodule disappeared within 2 months.