In primary breast cancer (BC), TILs are predictive of response to neoadjuvant chemotherapy and improved survival in triple-negative breast cancer (TNBC) and human epidermal growth factor receptor 2-positive (HER2+) BC, but their impact in hormone receptor-positive (HR+) BC remains unclear and may depend on distinct states of malignant cells or TILs3. This evidence concerns the gene ERBB2 and breast cancer.