BCR and chronic myelogenous leukemia, BCR-ABL1 positive: In the context of leukemogenic translocations, the breakpoint in KMT2A invariably occurs within an 8.3 kb region known as the breakpoint cluster region (BCR) (a specific region within the KMT2A gene, not to be confused with the BCR gene on chromosome 22 involved in CML), which separates the N-terminal portion (containing the CXXC domain) from the C-terminal portion (containing the SET domain) [2].