Univariate analysis in molecular subgroups emphasized that elevated TGIF expression was prognostic for both DFS and OS in ER-positive BC patients (DFS: HR 0.68 [95%CI 0.51–0.91]; log-rank p = 0.009, interaction p = 0.130; OS: HR 0.60 [95%CI 0.41–0.88], log-rank p = 0.008, interaction p = 0.107) and in the HER2-negative subgroup (DFS:HR 0.67 [95%CI 0.50–0.88], log-rank p = 0.004, interaction p = 0.034; OS: HR 0.57 [95%CI 0.40–0.81], log-rank p = 0.002, interaction p = 0.015). This evidence concerns the gene ESR1 and breast cancer.