To explore the relationship between the tertiary lymphoid structures (TLSs) and tumor-infiltrating lymphocytes (TILs), and their distribution characteristics as well as the prognostic value in gastric cancer (GC).

Material and methods:
The TLSs and four subtypes of TILs were assessed by immunohistochemistry (IHC) staining. The presence of MECA-79 positive high endothelial venules (HEVs) identified among the ectopic lymphocyte aggregation area in the GC tissue was defined as a valid TLSs.The number of labeled TILs were observed in 5 fields of the most positive cells in tumor center, invasive edge and within the TLSs, respectively, at a field of vision×40.

The TLSs distributed significantly higher in the tumor invasive edge than the tumor center (P <0.001). Similarly, the infiltrating density of CD8+T cells and GrB+T cells were highly distributed in the tumor infiltrating edge than the tumor center. While the total number of TILs and the FOXP3+T cells were on the contrary. There was a positive correlation between the density of TLSs and TILs either in the location or the immune phenotype. And a higher frequency of TILs and TLSs often associated with the favorable clinicopathologic parameters. Multivariate analysis revealed that the density of TILs (P= 0.019) and TLSs (P= 0.037) were the independent prognostic predictor for GC patients.

The formation of TLSs predicts an advantageous immune system function and can be considered as a novel biomarker to stratify the overall survival risk of untreated GC patients and as a marker of efficient immunotherapies.