The stability of NPM1 mutation, a consensus recommended MRD marker for AML, was reported to be 99%–100% in large cohorts [14,42], but the loss of NPM1 mutation at relapse has been observed in 7% to 25% of AML patients in smaller series [17,43,44,45,46,47]. This evidence concerns the gene NPM1 and acute myeloid leukemia.