Several reasons can be appointed for the presence of this heterogeneity: (1) clinical trials used different PD-L1 immunohistochemistry scoring assays [137]; (2) the scoring compartment differs for each specific therapy, namely pembrolizumab and nivolumab use PD-L1 tumor cell expression, whereas atezolizumab uses PD-L1 immune cell expression; (3) intratumoral heterogeneity; and (4) the sample available may not represent the full intratumoral heterogeneity [139]. The gene discussed is CD274; the disease is neoplasm.