KMT2A and precursor B-cell acute lymphoblastic leukemia: The most significant genetic diagnostic and prognostic factors for adult and paediatric B-ALL are: t(9;22)(q34;q11.2);BCR-ABL1;t(v11q23);KMT2A (MLL) rearrangements; t(12;21)(p13;q22);ETV6-RUNX1; high hyperdiploidy; near haploidy; low hypodiploidy; t(1;19)(q23;p13.3);TCF3-PBX1; intrachromosomal amplification of chromosome 21 (iAMP21) and t(17;19)(q22;p13.3);TCF3-HLF.