[An autopsy case of malignant histiocytosis showing a phenotype of S100 +lysozyme].

A 37-year-old Japanese man was admitted to our hospital because of high fever. The peripheral blood showed pancytopenia with a few erythrophagocytic histiocytes. A bone marrow aspirate revealed 12% immature histiocytes and 7% leukoerythrophagocytic histiocytes. A postmortem examination showed an infiltrative proliferation of immature histiocytes and erythrophagocytic histiocytes in the sinusoid of the liver, the urinary bladder, etc. These findings were consistent with malignant histiocytosis. In addition, these abnormal histiocytes showed a phenotype of S 100 protein +lysozyme.- In agreement with Watanabe's report, our findings suggest that malignant histiocytosis is the neoplasm of T-zone histiocytes.