ESR1 and breast cancer: This study aimed to investigate the association between TILs and Oncotype DX single gene scores for estrogen receptor (ER), progesterone receptor (PgR), and HER2 in HR+/HER2- breast cancer.<h4>Methods</h4>We retrospectively analyzed 260 patients with HR+/HER2- breast cancer who underwent surgery and Oncotype DX testing at Saitama Medical University International Medical Center between January 2022 and October 2024.