Prognostic Effect of Tertiary Lymphoid Structures in Epstein–Barr Virus–associated Gastric Carcinomas measured by Digital Image Analysis

Epstein–Barr virus–associated gastric carcinoma (EBVaGC) is characterized by prominent tumor-infiltrating lymphocytes (TIL) and has a favorable prognosis. Tertiary lymphoid structures (TLS), characterized by ectopic aggregated lymphocytes with high endothelial venules (HEV), are associated with favorable outcomes in various solid tumors. We hypothesized that EBVaGC, characterized by intense TIL, may be closely associated with TLS or HEV. To test this hypothesis, we digitally analyzed the TLS, HEV, and TIL in 73 surgically resected advanced EBVaGCs. For HEV, dual MECA-79 and CD31 dual immunohistochemistry were performed, and the ectopic expression of MECA-79 in tumor cells was measured.In 73 patients with EBVaGC, a high TLS ratio was found in 29 (39.7%) cases, high tumor-associated HEV density in 44 (60.3%) cases, and high CD8+ TIL density in 38 (52.1%) cases. Ectopic tumor expression of MECA-79 was observed in 36 patients (49.3%) cases. A low TLS ratio and tumor-associated HEV density were significantly associated with lymph node metastasis (p=0.005 and 0.042, respectively). Ectopic MECA-79 expression was significantly associated with lymph node metastasis (p=0.003). Patients with a low TLS ratio (p=0.038), low HEV density (p=0.042), and ectopic tumor MECA-79 expression (p=0.032) had significantly worse prognoses.In conclusion, the TLS ratio and HEV density affect the survival of patients with EBVaGC and may be related to the immune response that interrupts lymph node metastasis.