Impairment through epigenetic silencing or missense and frameshift mutations (see Table 1) of the TET1 enzyme has also been observed in myeloid malignancies, such as MDS, MPN, or AML [41, 42, 43], and is associated with lymphoid (B lineage) bias and increased HSC self‐renewal (see Fig. 1B). Here, TET1 is linked to acute myeloid leukemia.