CBFB and acute myeloid leukemia: In conclusion, prospective multicenter studies on larger patient cohorts are warranted to further assess biological and clinical features of NPM1-mutated MNs with blast count <20%, and to definitely investigate whether the observation of NPM1 gene mutations may become sufficient to define AML, irrespective of blast percentage found in PB or BM samples, as already established in the cases of core-binding factor AML harboring either RUNX1-RUNX1T1 or CBFbeta-MYH11 fusion transcripts [5,10,21,69].