Pleiomorphous histiocytic sarcoma arising in a patient with histiocytosis X.

An adult woman was followed up for the occurrence of multiple successive cutaneous and mucosal tumors of small size and classical histiocytosis X structure (histiocytoeosinophilic granuloma). In the second phase of the patient's clinical history there were successively appearing nodular or infiltrative cutaneous and subcutaneous tumors histologically resembling polymorphocellular sarcoma close either to malignant lymphogranuloma or to recently described "regressing atypical histiocytosis". Despite the marked cellular atypia and polymorphism the tumors exhibited a relatively favorable clinical course. Beside clearly sarcomatous structures, some of them displayed also transitional structures to histiocytosis X. Immunohistologically the atypical cells showed features of both the Langerhans' line and non-specific histiocytes. Ia-like antigen was positive in most of the elements. Quite occasional cells contained detectable amount of S-100 protein. Electronmicroscopy revealed quite sporadic structures resembling Langerhans granules.