Our understanding of the pathogenesis of Ph+ leukemias has improved, but several key features remain unexplained, such as the association of the m-BCR with Ph+ ALL and different responses of (m-BCR) p185BCR/ABL and (M-BCR) p210BCR/ABL-positive leukemia to TKIs. The gene discussed is BCR; the disease is acute lymphoblastic leukemia.