AFF1 and acute lymphoblastic leukemia: Among them, the fusion MLL-AF9 is associated more commonly with acute myeloid leukemia, whereas the translocation t(4;11)(q21;q23), which produces the fusion of the MLL and AF4 genes, has been documented in up to 80% of infant ALL cases and in near to 2% of children older than 1 year of age [62].