CD274 and neoplasm: Tumor and/or immune cell PD-L1 expression by immunohistochemical assays was first approved by the US Food and Drug Administration (FDA) as a companion diagnostic to pembrolizumab for advanced non-small-cell lung cancer, upper gastrointestinal cancers, cervical cancer, and urothelial cancer, based on convincing evidence for these malignancies (Herbst et al., 2016; Muro et al., 2016; Reck et al., 2016; Bellmunt et al., 2017; Chung et al., 2018; Fuchs et al., 2018).