MLLT3 and acute myeloid leukemia: Given that KMT2A/MLLT3 AML may be initiated in utero [202], it would be of interest to define the human fetal or embryonic cell of origin in which the KMT2A/MLLT3 preleukemic event occurs and determine if additional mutations and/or the fetal or early neonatal hematopoietic microenvironment differentially influence progression to AML in infants as opposed to older children.