[Cutaneous histiocytosarcoma: clinical, immunohistochemical and ultrastructural aspects; difficulties of study and problems of nosology (author's transl)].

Reporting a case of cutaneous tumor of the back of recent occurrence and rapid increase in a 79-years-old woman, according to Crosti's "reticulosis", the authors discuss the following points:--the histiocytic nature of the tumor cells particularly based on immunohistochemical studies (peroxidase activity, anti-HTLA serum) and on electron microscopy with special reference to the multivesicular bodies found in their cytoplasm;--the tests for correct identification of the histiocyte (including electron microscopy, tests for HTLA and HBLA antigens, peroxidatic reaction, acid phosphatase activity, and in vivo or in vitro phagocytosis);--the out of date character of the concept of malignant "reticulosis" in the hematologica and dermatologic classifications, the recent advances in the knowledge of the nature of the so-called "reticulum" (or "reticular") cell which seems to be a distinct entity derived from the mesenchymal cell (as the fibroblast);--the clinical and evolutive characteristics of histiocytic tumors (no hematologic involvement, slow evolution, high radiosensitivity), the difficulties in defining their malignancy and, above all, in finding comparable references in the literature with complete cellular study;--the nosologic place of this affection among the group of haematodermas and in the pathology of the mononuclear phagocyte system. The generic term of cutaneous histiocytosarcoma (stage I or II) is suggested, including the whole malignant and isolated tumoral proliferations developing from the dermic histiocyte.