A phase of chronic myelogenous leukemia characterized by one or more of the following: 1) Myeloblasts accounting for 10-19% of the peripheral blood white cells or of the nucleated cells in the bone marrow, 2) peripheral blood basophils at least 20%, 3) persistent thrombocytopenia that is unrelated to therapy, 4) persistent thrombocytosis despite adequate therapy, 5) increasing white blood cell count and increasing spleen size unresponsive to therapy, and/or evidence of clonal evolution. (WHO, 2001) [from
NCI]