However, after the first observation by Papadaki et al. that two among 21 (9.5%) NPM1-mutated AML patients experiencing relapse, lost NPM1 mutation at leukemia recurrence [32], many groups investigating NPM1-mutated molecular MRD provided further information on stability of NPM1 mutation at relapse, as summarized in Table 2. This evidence concerns the gene NPM1 and acute myeloid leukemia.