In a phase III trial, researchers examined the clinical relevance of tumour‐infiltrating lymphocytes (TILs) and breast cancer and found that TILs were lower in the ER‐positive/HER2‐negative subgroups compared with ER‐negative/HER2‐negative and HER2‐positive breast cancer subgroups (2.9% vs 10.6% and 11.1%).74 Here, ESR1 is linked to breast cancer.