BCR and acute lymphoblastic leukemia: In addition to the above referred genetic predisposition to childhood BCP-ALL, other recent studies also provide further evidence about the potential involvement of the residual hematopoiesis in BCP-ALL; thus, the presence of genetic alterations which are typical of leukemic blast cells (e.g. MLL and BCR-ABL1 gene rearrangements) have been also detected in mesenchymal stem cells [13] and residual neutrophils [14].