The diagnosis of CML is made by histopathology, cytogenetics, and the detection of the BCR-ABL1 fusion transcript by reverse transcriptase-polymerase chain reaction (RT-PCR) or of the Philadelphia chromosome translocation (9;22) by fluorescence in situ hybridization (FISH) [3]. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.