BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Depending on the breakpoint on chromosome 22 at the BCR (break point cluster) gene, three major isoforms of BCR-ABL1 can be produced: the 185kDa, 210kDa, and 230kDa proteins found in acute lymphocytic leukemia (ALL), chronic myeloid leukemia (CML), and chronic neutrophilic leukemia (CNL), respectively [2,3,4].