[Cutaneous sinus histiocytosis (Rosai-Dorfman disease)]

Sinus histiocytosis is as a rule a benign disease of lymph nodes, infiltrated by large histiocytes. These cells show typical cytophagocytosis, particularly lymphophagocytosis. Other organs may be also involved by this disease, often including the skin. Exclusive cutaneous sinus histiocytosis without infiltration of lymph nodes seems to be very rare. To exclude other non-X histiocytoses or histiocytosis-X, it is advisable to use immunohistochemistry. We report on a patient with sinus histiocytosis and discuss the problems of differential diagnosis.