A number of studies confirm that increased CD4+ and CD8+ TILs in CCA and extrahepatic biliary tract cancers (BTCs) are correlated with reduced lymph node metastases, decreased venous and perineural invasion and better overall survival [137,138,139]; consistently low CD8+ TILs are correlated with poor overall survival [140]. Here, CD4 is linked to cholangiocarcinoma.