[Primary cutaneous histiocytosarcoma. Incidence, characterization, course].

A case of true cutaneous histiocytosarcoma --or Crosti's reticulosis--is reported, and provides the basis for a discussion of the techniques at present used in defining the histiocytic origin of lymphomas, criteria for assessing the malignancy of histiocytic infiltrates, and clinical data and course of histiocytic sarcomas. Particular emphasis is laid on the characteristics of Crosti's reticulosis, which the authors consider to be a form of histiocytic sarcoma, usually with a favorable outcome. They also attempt to isolate pathological criteria for assessing the prognosis of the disease, which appears to vary substantially from case to case. Setting aside cases which had not been studied by both ultrastructural and enzymo-immunological techniques, the authors found only the twenty-two cases of primary cutaneous histiocytosarcoma in dermatological literature, including their own.