Malignant histiocytosis showing ascites and recurrent meningeal infiltration

Report is made of a case of malignant histiocytosis (MH) in which abdominal effusion and recurrent meningeal symptoms due to tumor cell infiltration appeared. The diagnosis of malignant histiocytosis was made by histologic examination of biopsy materials from the right submandibular mass. The specimens from the ascites and the liquor from a lumbar puncture showed three types of cells: normal-appearing histiocytes, large, atypical histiocytic cells and bi-and multinucleated cells. Phagocytosis was observed in the normal-appearing histiocytes and the large atypical cells; similar findings were observed in the specimens from marrow. The autopsy findings showed a systemic, diffuse, nontumorous proliferation of morphologically atypical histiocytes. Although ascites or meningeal symptoms caused by infiltration of neoplastic histiocytes are extremely rare, the possibility of MH should be considered in diagnosing conditions such as observed in this case.