CD274 and hepatocellular carcinoma: Taking the research by Gao et al. as an example [14], mouse anti-PD-L1 antibody was used for the IHC analysis; however, they did not distinguish the PD-L1 staining of HCC tumor cells in cell membrane and cytoplasm, and differentiated the ‘high’ and ‘low’ PD-L1 expression according to the density of staining.