BCR and chronic myelogenous leukemia, BCR-ABL1 positive: In chronic myelogenous leukaemia (CML), a reciprocal translocation (9; 22) (q34; q11), known as the ‘Philadelphia chromosome’ (Ph), results in the formation of a mutated tyrosine kinase protein, called Abelson‐Breakpoint Cluster Region (BCR/ABL).