BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic Myeloid Leukemia (CML) is characterized by a balanced translocation, fusing the Abelson oncogene (ABL1) on chromosome 9q34 with the breakpoint cluster region (BCR) on chromosome 22q11.2, t(9;22)(q34;q11.2), more commonly known as the Philadelphia chromosome.