Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder resulting from the neoplastic transformation of the primitive hematopoietic stem cell. The disease is monoclonal in origin, affecting myeloid, monocytic, erythroid, megakaryocytic, B-cell, and, sometimes, T-cell lineages. Bone marrow stromal cells are not involved.

CML accounts for 15% of all leukemias in adults. Approximately 8,220 new cases of CML will be diagnosed in 2016, with an estimated 1,070 deaths. The age-adjusted incidence is 1.6 per 100,000 population. With imatinib therapy, the annual mortality has been reduced significantly (to less than 2% to 3% per year, with further mortality reductions after the first 2 to 3 years). This has resulted in an increase in prevalence from approximately 70,000 patients in the US in 2010 to a projected 144,000 in 2030.