PD-1/PD-L1 inhibitors are widely recommended for a variety of solid tumors, and pembrolizumab, with/without chemotherapy, is recommended for HER2-negative or immune biomarker positive (for example, microsatellite instability-high and mismatch repair deficient) patients with breast cancer, according to current breast cancer guidelines (7). The gene discussed is PDCD1; the disease is breast cancer.