In this regard, the activation of the PD-1/PD-L1 pathway has a central role, witnessed by the expression of PD-L1 by multiple cell types within the OPMD microenvironment (tumour-associated macrophages, fibroblasts, lymphocytes), and by the fact that PD-L1 expression in epithelial and subepithelial cells is associated with malignant transformation [10]. The gene discussed is CD274; the disease is neoplasm.