The molecular hallmark of CML is the Philadelphia chromosome (Ph) that originates from the reciprocal translocation t (9; 22) (q34; q11), between the breakpoint cluster region (BCR) and the Abelson tyrosine kinase (ABL), which produces a fusion gene BCR-ABL[23]. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.