In terms of biomarkers, it is worth noting that, although some studies suggest that PD-L1 is more frequently expressed by tumor cells in NECs than in NETs [17, 18], there are only few investigations exploring PD-L1 expression in association with the evaluation of TILs and microsatellite instability or mismatch repair (MMR) deficiency status, which are all associated with potential effectiveness of ICIs in re-activating anti-cancer immune response [19–22]. The gene discussed is CD274; the disease is cancer.