Multinucleate cell angiohistiocytoma with hypertrophic nerves

Multinucleate cell angiohistiocytoma (MCAH) represents a rare benign skin lesion characterized by multiple papules that are usually found on the distal extremities or face of middle-aged women. We report on a 60-year-old male with a history of monoclonal gammopathy and severe rheumatoid arthritis who had several asymptomatic red-to-livid papules grouped on the right side of his trunk. The lesions had been present for a few years and were gradually enlarging. Biopsies from three lesions showed a spectrum of changes consisting of a proliferation of small venules together with thickened collagen bundles and increased numbers of interstitial cells including bizarre, multinucleated giant cells. Immunohistochemically, the multinucleated cells were positive for vimentin and lysozyme while the interstitial cells expressed CD68, factor XIIIa and lysozyme. Interestingly, strikingly enlarged dermal nerves were seen in all the three biopsies and two of the biopsies showed an accompanying infiltrate of lymphocytes and plasma cells.