BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm that accounts for approximately 15% of the incidence of adult leukemia.[1] One out of every 500 to 600 individuals is diagnosed with CML in his or her lifetime.[1, 2] In almost all cases, CML is caused by a BCR-ABL gene translocation (i.e., Philadelphia chromosome positive).