The ubiquitously expressed and evolutionarily conserved gene encoding NPM, NPM1 (Gene ID 4869, mapped at 5q35.1, genomic NCBI Reference Sequence NG_016018.1, Ensembl ENSG00000181163), is mutated in 25–35% of adult patients with primary acute myeloid leukemia (AML) and 46–64% of adult patients with normal karyotype AML (NK-AML) [3–5]. The gene discussed is NPM1; the disease is acute myeloid leukemia.