CD274 and cancer: Uncertainty arises from the different antibody kits used [60], but also from the examined tissue: besides differences in PD-L1 expression in different types of cancer tissue, dynamic expression varying in intensity depending on location, prior treatments, and inhomogeneous expression inside tumor tissue [61], it has been suggested that PD-L-1 expression should be assessed in the immune and stromal cells of the tumor microenvironment [59], as well as extratumoral sites such as lymph nodes, blood, and bone marrow [62].