Reticulohistiocytoma of the dorsum.

To clarify the nature of reticulohistiocytoma of the dorsum, 19 cases, including three of the seven original cases described by Crosti, were evaluated clinically, histologically, and immunologically. In seven cases gene rearrangement analysis was also performed. Results indicate that reticulohistiocytoma of the dorsum must be considered a primary cutaneous B cell lymphoma of follicular center cell origin. This localized skin disease has a very slowly progressive course, with many patients showing no systemic involvement even after prolonged follow-up.