only validated biomarker in many prospective trialspositivity for PD-L1 expression was defined using different values of PD-L positive tumor cells percentageevaluation of percentage of tumor area infiltrated with immune cells expressing PD-L1 is extremely difficult and uselessexpression was tested with different platformstumor tissue could demonstrate heterogenicity for PD-L1 expressionPD-L1 expression could depend on the histological type of tumor cells and patients’ history of treatment. The gene discussed is CD274; the disease is neoplasm.