BCR and chronic myelogenous leukemia, BCR-ABL1 positive: CML is characterized by a well-known chromosomal translocation, the Philadelphia chromosome or t(9; 22) (q34; q11), during which, a large part of the Abelson (ABL1) oncogene on chromosome 9 is translocated to the breakpoint cluster region (BCR) of the long arm of chromosome 22, resulting in a BCR-ABL1 fusion gene.