Poor prognosis in Epstein–Barr virus-negative gastric cancer with lymphoid stroma is associated with immune phenotype

Background Gastric cancer with lymphoid stroma (GCLS) is pathologically characterized by poorly developed tubular structures with a prominent lymphocytic infiltration. Its clinical and prognostic features differ in patients positive and negative for Epstein–Barr virus (EBV) infection. This study analyzed the expression of programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), and the density of tumor-infiltrating lymphocytes (TILs) including CD3+ and CD8+ T cells, as well as their prognostic significance in patients with GCLS. Methods The study included 58 patients with GCLS (29 EBV+ and 29 EBV−) who underwent curative resection. Expression of CD3, CD8, PD-1, and PD-L1 in tumor cells and TILs was analyzed using a quantitative multispectral imaging system (Opal™), with these results validated by immuno-histochemical assays for PD-L1 on whole slide sections. Results The proportion of tumors overexpressing PD-L1 (31.0 vs. 0%, P = 0.002), TIL density (4548 vs. 2631/mm 2 , P < 0.001), and intra-tumoral CD8+ T-cell density (2650 vs. 1060/mm 2 , P < 0.001) were significantly higher in EBV+ than in EBV− GCLS. In addition, CD8+/CD3+ T-cell ratio was higher in EBV+ than in EBV− GCLS (55.3 vs. 35.8%, P < 0.001). Lower TIL density, defined as < 1350/mm 2 , was a significant negative factor of survival. Conclusions Despite histopathological similarity, quantitative multispectral imaging revealed differences in the tumor immune micro-environment between EBV+ and EBV− GCLS, indicating that the underlying pathogenesis differs in these two disease entities. TIL density may be a prognostic marker in patients with GCLS.