CD274 and breast carcinoma: Firstly, the overexpression of PD-L1 is associated with a more aggressive phenotype and a poorer prognosis in some cancers, such as gastric cancer, hepatocellular carcinoma, renal-cell carcinoma, esophageal cancer, pancreatic cancer, ovarian cancer, bladder cancer, and breast cancer [44,45,46,47,48,49,50,51].