RESUMEN
Malignant histiocytosis is a rare, usually fatal malignant neoplasm of reticuloendothelial systems. The disease is associated with fever, malaise, weight loss, hepatosplenomegaly, lymphadenopathy, pancytopenia, jaundice, and purpura. A 44-year-old female patient is described who had multiple, purple crusted nodules and plaques in the skin. In the laboratory study, pancytopenia was noted on the peripheral blood. In addition many atypical histiocytes were seen on the bone marrow aspiration. A lesional biopsy showed nodular infiltrations of atypical histiocytes in the dermis and some erythrophagocytosis was seen. Immunohistochemically, the histiocytes were weakly stained for lysozyme and α-l-antichymotrypsin, but were unstained for S-100 protein, cytokeratin, CEA(carcinoembryonic antigen), pan T/B marker CD30(ki-1), UCHL-1 LCA(leukocyte common antigen), and α-l-antitrypsin.