CD274 and carcinoma: In this series, carcinoma cells expressed programmed death-ligand 1 (PD-L1) in all cases of CCA derived from IPNB were frequently associated with PD-L1-positive mononuclear cells, PD-1-positive lymphocytes and CD8-positive lymphocytes infiltrating within the tumor, suggesting that the PD-1/PD-L1 axis was aberrantly activated and favorable response to immune checkpoint inhibitor therapy could be promising [147,148].