[Multicenter skin tumor of the interdigitating dendritic cell].

This report concerns a multicentric skin tumor of dendritic cells. Skin-colored to reddish-brown papules and nodules erupted on the right arm of a 68-year-old man and, during the following years, spread to the upper extremities, shoulders, legs and face. Immunohistochemically the large, histiocyte-like tumor cells are Leu-6 (CD1), Leu-3a (CD4), HLA-DR/DQ and S-100 protein positive, but on thorough ultrastructural investigation were found to lack Birbeck granules. Thus, this disease represents a skin tumor of the interdigitating dendritic cell, an accessory cell which, in this case, was associated with a high content of T-lymphocytes within the cutaneous cellular infiltrate. The clinical course is characterized by periodic progression with intermittent, spontaneous regression. During a 7-year follow-up it was not possible to ascertain involvement of either lymph nodes or internal organs.