BCR and chronic myelogenous leukemia, BCR-ABL1 positive: The breakpoints in the ABL gene usually occur at exon a2, but in the BCR gene, there are three main types has been observed: the M-bcr which breakpoints cluster region usually located in exons e12-e16(also known as b1-b5), e13a2(b2a2) and e14a2(-b3a2), encoding a 210-KDa protein and mainly seen in CML; the m-bcr, ela2, encoding a 190-KDa protein and usually associating with B-ALL; the u-bcr, e19a2, encoding a 230-KDa protein and mainly causes mature neutrophils hyperplasia3,4.