[Essential thrombocythemia transformed to minimally differentiated acute myeloid leukemia]

A 64-year-old female diagnosed for essential thrombocythemia was treated with MCNU 50 mg four times in the course of the disease. Six months after the last administration, in May 1991, she was admitted because of decreasing thrombocyte count and appearance of blasts in the peripheral blood. On admission, laboratory findings were as follows: WBC 700/microliters with 5% of blasts, RBC 331 x 10(4)/microliters, and PLT 17.9 x 10(4)/microliters. Bone marrow aspiration revealed hypocellular marrow with 39% blasts. About 5% of the blasts were positive for myeloperoxidase by electron microscopy analysis. Leukemic cells were positive for CD 7, 13, 33 and 34, negative for other lymphoid lineage markers, and demonstrated no rearrangement of TCR-beta, gamma and IgH genes. Although she was treated with low-dose cytosine arabinoside, no response was observed. Subdural hematoma and sequential pneumonia developed and the patient died eight months after leukemic transformation. In conclusion, we think that the leukemic transformation might have been developed in the natural course of essential thrombocythemia in the present case. However, we cannot exclude the influence of MCNU.