Chronic myeloid leukemia (CML) is estimated at approximately 1 to 2 cases per 100,000 individuals and accounts for approximately 15% to 20% of all patients with leukemia. CML is a clonal disease characterized by balanced translocation between chromosomes 9 and 22 (Philadelphia chromosome). The resulting BCR-ABL gene has abnormal tyrosine kinase activity which stimulates cell growth and is responsible for the transformed phenotype of CML cells. The disease is characterized by a triphasic course that includes a chronic phase (CP), an accelerated phase (AP) and an acute or blastic phase (BP). Unless the disease is controlled or eliminated, patients progress to AP and BF in variable periods of time. Several staging classification systems are used for CML all of which were designed in the pre-imatinib era. In this article we discuss the natural history of CML and phase definitions according to the most useful criteria.
CML; classification; staging; prognostic factors; disease progression
