NPM1 and acute myeloid leukemia: Additionally, NPM1 has been shown to be a reliable molecular biomarker of disease, which is retained in > 90% of relapsed patients who initially had mutated NPM1 at AML diagnosis (9, 14, 15); thus, interrogation of mutant NPM1 can be used to identify minimal/measurable residual disease (MRD) and/or early relapse, post-therapy.