BCR and chronic myelogenous leukemia, BCR-ABL1 positive: For example, on the cellular level, CML is associated with a specific chromosomal abnormality, T (9;22) is reciprocally transposed to form the Philadelphia (PH) chromosome, and the C−ABL proto-oncogene on chromosome 9 and the BCR (breakpoint cluster region) gene on chromosome 22 lead to the PH chromosome.