NPM1 and acute myeloid leukemia: NPM1-rearrangements (cases 212–215), such as NPM1::OSCP1 (n = 1; case 215), NPM1::MLF1 (n = 1; case 214) and NPM1::CCDC28A (n = 2; cases 212 and 213) exclusively occurred in AML subtype M4 (n = 4/4) and preferably in infant patients (n = 3/4; cases 212, 213 and 215).