ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myelogenous leukemia (CML) is a hematopoietic stem cell disorder characterized by the Philadelphia chromosome, the result of a gene mutation of translocation between chromosomes 9 and 22, which fuses the BCR gene with the ABL1 gene and produces the constitutively active BCR-ABL1 (Bcr-Abl) tyrosine kinase, directly leading to the proliferation of leukemia cells.1