DNA hypomethylation is mediated by TET family, which oxidized 5‐methylcytosine (5mC) iteratively, followed by TDG excision.[27] We first analyzed the correlation between TET1, TET2, TET3, TDG and POU4F1 in breast cancer patients in TCGA cohort. The gene discussed is TET2; the disease is breast carcinoma.