BCR and chronic myelogenous leukemia, BCR-ABL1 positive: The ABL kinases were initially identified as oncogenes in the context of patients with chronic myelogenous leukemia (CML) and acute lymphocytic leukemia (ALL) who presented with BCR-ABL1 fusion proteins due to a chromosomal translocation of ABL1 to the Breakpoint Cluster Region (BCR) gene sequences [9].