In 60 to 80% of all patients with Ph-positive ALL, the breakpoint occurs in the first intron of the BCR gene, in a region referred to as the minor breakpoint cluster region (m-bcr), thereby producing the shorter isotype p190 BCR-ABL1 from the e1a2 type mRNA (Deininger et al., 2000). Here, BCR is linked to acute lymphoblastic leukemia.