NUP98 and acute myeloid leukemia: Unbalanced cytogenetic abnormalities, like del(5q), have emerged as secondary mutations in two AML subtypes with pre-existing cryptic abnormalities: t(5;11)(q35;p15)/NUP98-NSD1 and the infrequent t(7;21)(p22;q22)/RUNX1-USP42.