Aim: Previous studies have focused on the subpopulations of tumor-infiltrating lymphocytes (TILs) in tumors. This study focuses only on the concentration of TILs in the tumor irrespective of type and elucidates its prognostic value.

Methods: We used 315 HCC patients as the discovery phase and another 343 HCC patients as the validation phase. By following the standardized guideline, density of TILs were categorized into low (TILs < 10%), intermediate (10% ≦ TILs < 50%), and high (TILs ≧ 50%) levels. Associations of TILs with prognostic, immune-related, and genetic variables were examined.

Results: We observed a dose-response relation of TILs with overall survival (intermediate: HR, 0.58; 95% confidence interval (CI), 0.36-0.93; high: HR, 0.37; 95% CI, 0.15-0.93) and disease-free survival (intermediate: HR, 0.35; 95% CI, 0.22-0.58; high: HR, 0.23; 95% CI, 0.09-0.58). The prognostic value of TILs was validated in the TCGA set. Mutation burden or the number of neoantigens were not associated with TILs intensity. However, hepatitis B or C virus infection patients had higher TILs intensity in the para-tumor tissue.

Conclusions: The TILs intensity was associated with patients' survival. If confirmed, this would suggest that clinical routine assessment of TILs could provide prognostic information in HCC.