Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by the Philadelphia chromosome, a translocation of chromosomes 9q34 and 22q11, that creates the fusion oncogene BCR::ABL1 encoding a constitutively activated tyrosine kinase (TK) mutant1. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.