CD274 and breast carcinoma: Recent studies have confirmed that M2 macrophages, which exist in large numbers in the tumor microenvironment, can evade T-cell-mediated immune surveillance by inducing the upregulation of PD-L1 and promote the progression of breast cancer by promoting angiogenesis, immune escape, and immunosuppression37,38, while M0 macrophages are closely associated with distal metastasis of tumor cells and poor prognosis39.