Five cases of cutaneous Rosai-Dorfman disease.

Rosai-Dorfman disease (RDD), previously known as sinus histiocytosis with massive lymphadenopathy, is a benign, idiopathic histiocytic proliferative disorder. It commonly affects lymph nodes, but any organ of the body may be involved. Histological findings include characteristic large, pale, histiocytic cells (Rosai-Dorfman cells) exhibiting cytophagocytosis. Immunohistochemically, these histiocytes are positive for S-100 protein and CD68, but stain negatively for CD1a. On electron microscopy, Birbeck granules are absent. RDD limited to the skin is rare, less than 30 cases having been reported to date. We present five further cases of purely cutaneous RDD. Three presented as solitary nodules and one as a large, well-circumscribed plaque. The fifth patient, who was HIV positive, had a rosacea-like facial eruption.