CD274 and neoplasm: Recent evidences suggested two different pathways modulating the PD-L1 expression on the tumor cell surface: the “inflammation-driven”, INF-gamma-mediated, PD-L1 expression, which is localized at sites of inflammation and is usually associated with a baseline tumor T-cell infiltration; and the “oncogene-driven”, PD-L1 expression, which is constitutive, not increased by the inflammation process and associated with neither an immune response nor a T-cell tumor infiltration [39, 40].