ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myeloid leukemia (CML) is a clonal hematopoietic stem cell disorder caused by a reciprocal balanced translocation between the ABL1 locus and the BCR regions in the long arms of chromosome 9 and 22, respectively, which results in the formation of the BCR‐ABL1 fusion gene.