KMT2A and acute lymphoblastic leukemia: The presence of early bipotential B-macrophage progenitors in the bone marrow and the fact that MLL-positive B-ALL show gene expression profiles consistent with early hematopoietic progenitors have raised the possibility that early bipotential or oligopotential progenitor cells are target for leukemogenic translocations, and constitute the origin of lineage switching events [65] (Figure 2, upper panel).