PDCD1 and non-small cell lung carcinoma: The use of immune checkpoint inhibitors (ICIs) targeting programmed cell death protein 1 (PD-1) as single-agent or in combination with chemotherapy is conditioned by ligand (PD-L1) expression; indeed, in Europe the use of single-agent ICI (such as pembrolizumab, atezolizumab, cemiplimab) is reserved to patients whose NSCLC harbors high PD-L1 expression (≥ 50%), while combinations (such as chemotherapy plus pembrolizumab or chemotherapy plus ipilimumab plus nivolumab) are employed in case of PD-L1 between 0–49%.