Regardless of its physiological role in preventing autoimmunity, the expression of PD-L1 has been observed in tumor cells and tumor stroma, in particular cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), and vascular endothelial cells (ECs) [65–67]. This evidence concerns the gene CD274 and neoplasm.