CD274 and neoplasm: Monoclonal antibodies targeting the co-inhibitor T cell receptors Programmed Death-1 (PD-1) or its ligand (PD-L1)—and, more recently, Cytotoxic T Lymphocyte Antigen-4 (CTLA-4)—have proven successful in terms of survival benefit, and are now widely used as monotherapy or in combination [6].For treatment of LC, PD-L1 expression assessed with immunohistochemistry using the tumor proportion score (TPS), is the only licensed predictive biomarker of response to checkpoint inhibitors available so far—although encumbered by several limitations [7,8].