Among breast carcinoma subgroups, low TET2 expression was associated with poorer OS in estrogen receptor (ER)‐negative (HR [95% CI] = 2 [1.25–3.125], p = 0.0027), human epithelial growth factor receptor 2 (HER2)‐negative (HR [95% CI] = 1.59 [1.15–2.17], p = 0.0044), progesterone receptor (PR)‐negative (HR [95% CI] = 1.22 [0.64–2.33], p = 0.55), grade 1 (HR [95% CI] = 1.37 [0.12–16.6], p = 0.8), and grade 3 (HR [95% CI] = 1.72 [1.03–2.86], p = 0.025) breast carcinomas, and breast carcinoma with lymph node involvement (HR [95% CI] = 0.47 [0.29–0.77], p = 0.0023) (Table 3). This evidence concerns the gene ERBB2 and breast carcinoma.