CD274 and breast cancer: Further detailed mechanisms of sEVs in the metastasis development of BC were explored by bioinformatics analysis, RT-qPCR, WB and luciferase reporter assay.<h4>Results</h4>In this study, we identified that the immunosuppressive molecule PD-L1 was more abundant in TAMs than in BC cells, and a specific PD-L1 + CD163 + TAM subpopulation was found to be associated with metastasis BC.