In two patients in whom serial samples during the conversion from MPN to CMML were available, it was shown that the JAK2 V617F variant allele frequency (VAF) in both patients markedly dropped, whereas the VAF in other genes that are commonly found in CMML concomitantly increased, suggesting that the CMML-like phenotype in these patients was driven by a genotype without the contribution of the JAK2 mutation (Figure 2). Here, JAK2 is linked to chronic myelomonocytic leukemia.