TET2 and chronic myelomonocytic leukemia: TET2 mutations (chromosome 4q24) are frequent and are thought to be the driver mutations in CMML.7 TET2 catalyzes the conversion of 5-methyl-cytosine to 5-hydroxymethyl-cytosine, regulating methylation and transcription.8 The prognostic relevance of TET2 mutations remains unclear with some studies demonstrating favorable,9 unfavorable10 and no impact1 on overall survival (OS).