It has been found that PD-L1 is significantly more expressed in breast cancer tissues, especially in triple-negative breast cancer than in normal breast tissue, and the safety and efficacy of PD-L1 inhibitor pembrolizumab in triple-negative breast cancer, hormone receptor positive, HER2-negative, local recurrence or metastatic breast cancer are significantly enhanced64,65. This evidence concerns the gene ERBB2 and triple-negative breast carcinoma.