[Acute myelomonocytic leukemia with mastocytosis in bone marrow]

A 22-year-old female was admitted to our hospital because of general fatigue. The lymph nodes, liver and spleen were not palpable. She was without cutaneous lesions. Haematological examinations revealed leukocytes 3,200/microliters with 44% blasts of myelomonocytic origin, and platelets 15,000/microliters. Bone marrow smears were hypercellular marrow with 51% blasts of myelomonocytic origin and focal involvement of mast cells. Serum histamine and vitamin B12 level was high. Mast cells were round with rounded or segmented nuclei. The nucleoli were inconspicuous and the cytoplasm contained a number of metachromatic granules. Cytochemically, mast cells stained positive for alpha-naphthol-AS.D-chloroacetate esterase and acid phosphatase, and negative for peroxidase, Sudan black B and alpha-naphthyl butylate esterase. In toluidine blue staining, mast cells had stained similarly with pH values from 2.5 to 6.5. She was diagnosed as acute myelomonocytic leukemia with benign mastocytosis, and treated with BH.AC-DNP. A complete remission was obtained, but mast cells in the marrow did not decrease. Relationship between leukemia and mastocytosis was not known, but it was suggested that mast cells responded to the proliferation of the leukemic cells.