PDCD1 and breast cancer: Primary breast cancer (PBC) with axillary lymph node metastasis (ALNM+) is associated with distinct clinical outcomes, including reduced survival (The Cancer Genome Atlas/Foshan cohorts, P < 0.05) and an attenuated response to anti-programmed cell death protein 1 antibody/anti-programmed death-ligand 1 antibody (anti-PD-1/anti-PD-L1) therapy.