This chromosome forms the BCR/ABL1 fusion gene.     ///    "We observed a rare case of adult Ph-positive (Ph(+)) ALL, in which the BCR/ABL1 fusion transcript was not detected using the ABL1 exon a2 region primer. "    ///    Adult acute lymphoblastic leukemia with a rare b3a3 type BCR/ABL1 fusion transcript..     ///    "If the BCR/ABL1 fusion transcript is undetected with the ABL1 exon a2 region primer in Ph(+) ALL cases, an RT-PCR analysis that can detect the b3a3 type BCR/ABL1 fusion transcript should be considered to improve diagnosis. "