A 50-year, old patient tSCIILS wnn n1 ea i-,ess and bleeding episodes. His leukocyte count was 48 x 109 cells/L and platelet count was 50 x 109 cells/L. There was dysplasia of neutrophils with a differential count showing 76% neutrophils, 8% blast cells, 12% myelocytes and metamyelocytes and 4% other cells Bonemarrow examination showed 14% blasts. Cytogenetics showed t(8, 21). The most likely diagnosis is: