NPM1 and acute myeloid leukemia: However, our present study did not reveal any sequence variation in the 120 MPN patients and 9 MDS/MPN patients we studied, as shown in Figures 2(a) and 2(c), while Figures 2(b) and 2(d) showed the chromatograms of positive controls (samples from AML patients with FLT3-ITD or NPM1 mutation; Figure 2(b) showed the FLT3 internal tandem duplications mutation in exons 11 and 12; Figure 2(d) showed the insertion of a TCTG tetra nucleotide at positions 956 to 959 of the reference sequence).