Regardless of the precise frequency, the identification of these patients is important from a clinical point of view in 2 aspects: first, in regard to the classification as AML-MRC (applying the WHO morphologic criteria) or as AML with NPM1 mutation (using the WHO genetic criteria), and second, because multilineage dysplasia has no impact on the biologic, clinicopathologic, and prognostic features of AML with mutated nucleophosmin [37]. The gene discussed is NPM1; the disease is acute myeloid leukemia.