TET2 is one of the epigenetic regulator genes and frequently mutated in hematological malignancies, including CML.24 Wang et al. performed systematic mutation analysis by WES of PV and found recurrent somatic mutations in ASXL1, DNMT3A, TET2 and SF3B1.25 Ortmann et al.26 reported TET2 mutations in JAK2 mutation-positive MPN patients to clarify the effect of mutation order on disease phenotype and progression. The gene discussed is TET2; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.