BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Most cases of CML are caused by a chromosomal translocation, called the Philadelphia chromosome, in which the break point cluster (BCR) gene on chromosome 22 and the Abelson (ABL) non‐receptor type tyrosine kinase gene on chromosome 9 are fused, resulting in the chimeric oncogene, BCR‐ABL (Faderl et al, 1999).