NK cells can account for up to 50% of total intrahepatic lymphocytes.4 Tissue microarray experiments using anti-TM4SF5 antibody showed that more than half of HCC tissues from patients had TM4SF5-positive immunostaining, whereas their normal liver tissue counterparts, cholangiocarcinoma tissues, and liver adenocarcinoma tissues metastasized from the rectum were TM4SF5-negative, suggesting that TM4SF5 is relevant in HCC but not in other types of liver cancer (Fig. 1e). Here, TM4SF5 is linked to hepatocellular carcinoma.