BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myeloid leukaemia (CML) is clonal stem cell disorder driven by the BCR-ABL1 fusion gene resulting from a reciprocal translocation between chromosomes 9 and 22 (the Philadelphia (Ph) chromosome) that gives rise to an aberrant chimeric tyrosine kinase (TK) (reviewed in1).