ESR1 and breast cancer: Denkert et al. [2] showed that stratifying ER+, HER2 normal breast cancers in high/low Ki67 did not change the overall prognostic effect of TILs, whereas Fujimoto et al. [20] demonstrated that high TILs were associated with favourable DFS in Ki67-high, but not in Ki67-low ER+, HER2 normal breast cancer.