One such candidate biomarker is the expression of PD-L1, an immune check point ligand, expressed by tumors cells or tumor-associated immune cells, acting as an effective tumor mechanism to evade immune-mediated destruction [10]; positive immunostaining correlates with response to anti-PD-1 agents in non-small cell lung cancer (NSCLC) but is not a universal marker in other tumor types [11]. This evidence concerns the gene PDCD1 and neoplasm.