NRAS and leukemia: The three patients who progressed to leukemia (MPN02 and MPN04) or to an accelerated phase (MPN18) showed a higher number of mutations compared to the other patients (mean = 19.3 + /− 7.2 vs. 11.8 + /− 4.6; p = 0.17 two-sided Mann–Whitney test), and all of these three cases developed mutations in KRAS or NRAS over time.