According to the preset thresholds of GS and MM, 25 DEGs in the black module had the strongest correlation with the PD-1/PD-L1 pathway in breast cancer, and it suggested that these 25 genes were closely related to cytokines and T cell function (KEGG analysis) in the PD-1/PD-L1 pathway and might be the essential genes related to the PD-1/PD-L1 pathway in breast cancer. This evidence concerns the gene PDCD1 and breast cancer.