Goeppert et al. [36] analysed the impact of tumour-infiltrating immune cells on CCA outcomes, suggesting that intraepithelial infiltrating CD4+ and CD8+ T lymphocytes resulted in better overall survival, which was also seen in patients having a higher total regulatory T lymphocytes; the conclusion of this study was that the adaptive immune system plays a role in fighting tumour cells, potentially leading to longer survival. Here, CD4 is linked to neoplasm.