CD274 and renal cell carcinoma: PD-L1 is also expressed on tumor cells in several cancer types and its expression implies a weakened host immune response and consequent poor prognosis in several malignancies as malignant melanoma, lung cancer (NSCLC), thymoma, bladder, ovarian, renal cell carcinomas (RCC) [15, 16], and GEP-NEN [17].