CD274 and neoplasm: Tumor-associated macrophages (TAMs), which could be major population in MPE, often increase chemo-resistance and regulate immunity by reducing T cell activation, potentially through the interaction of programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) or through the release of immunosuppressive molecules, such as transforming growth factor-β (TGF-β) and interleukin (IL)-10 [5, 7, 8].