NPM1 and acute myeloid leukemia: However, the occurrence of cytogenetic abnormalities as well as genetic mutations identifying specific WHO entities (e.g., NPM1, FLT3, CEBPA mutations) is lower in pediatric than in adult AML, and a high percentage of pediatric patients (>40%) fall in the “AML not otherwise specified” (AML-NOS) category, thus limiting the applicability of WHO classification in children with AML (5).