BCR and acute lymphoblastic leukemia: The well-known subgroups of pediatric ALL based on expressed fusion genes include BCR-ABL1, ETV6-RUNX1, TCF3-PBX1, and 11q23/MLL rearrangements, such as KMT2A-AFF1, KMT2A-MLLT3, KMT2A-MLLT1, and KMT2A-MLLT10.