ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the Philadelphia (Ph) chromosome arising from a reciprocal translocation of genes between chromosomes 9 and 22, which generates the breakpoint cluster region–Abelson tyrosine kinase 1 (BCR-ABL1) fusion gene that encodes a constitutively active tyrosine kinase driving uncontrolled myeloid proliferation [1,2,3,4].