KMT2A and acute myeloid leukemia: The most problematic issue of molecular MRD is its limited applicability in children, i.e., major fusions (e.g., RUNX1::RUNX1T1, CBFB::MYH11, PML::RARA, KMT2A::MLLT3) are found in less than 40% of children with AML and major gene mutations found in adults (e.g., NPM1c, FLT3-ITD) are far less prevalent in children.