Chronic myeloid leukemia (CML) is a myeloid neoplasia characterized by the mutual translocation between chromosome 9 and 22 (Philadelphia chromosome) and by the BCR-ABL1 rearrangement, with a consequent synthesis of an uncontrolled tyrosine-kinase that induces increased proliferation, reduces apoptosis, and causes the entry of myeloid immature cells into the bloodstream (Rowley, 1973). The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.