ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myeloid leukemia (CML) is a malignant disease of a primitive hematopoietic cell, characterized by a reciprocal translocation between chromosomes 9 and 22, and creates the fusion gene BCR-ABL1, which is a deregulated tyrosine kinase that drives the leukemia.1 CML treatment has been significantly improved.