ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myeloid leukaemia (CML) is a myeloid stem cell neoplasm characterized by uncontrolled accumulation and expansion of myelopoietic stem and progenitor cells and the reciprocal chromosomal translocation t(9;22) that creates the fusion oncogene BCR‐ABL1.