Spatial specificity of Epstein-Barr virus infection in gastric cancer: A 44-case clinicopathological analysis

Epstein-Barr virus (EBV) is detected in ~10% of gastric cancer (GC) cases, but whether it directly drives carcinogenesis or merely colonizes established tumors remains unclear. The present study aimed to characterize the clinicopathological features and infection patterns of EBV-positive GC (EBVaGC) and to explore their translational implications. EBV-encoded RNA in situ hybridization was performed to identify EBVaGC cases among 456 patients with GC. Immunohistochemistry was used to assess Ki-67, proliferating cell nuclear antigen (PCNA) and claudin 18.2 (CLDN18.2) expression. Clinicopathological characteristics and survival data were analyzed. Of the 456 patients, 44 (9.6%) were EBV-positive. EBVaGC predominantly occurred in men and often presented as focal ulcerative masses with diverse histologies. No significant differences were observed in terms of age, tumor size, tumor/node stage, or long-term prognosis between EBV-positive and -negative groups (P>0.05), although EBV-positive patients showed better short-term outcomes (defined as 12-month survival rate; P=0.046). Notably, EBV infection was spatially restricted, being detected in cancer cells and in a subset of adjacent high-grade intraepithelial neoplasia (HGIN) tissues (25%), but absent in all non-neoplastic gastric mucosal cells examined, including chronic gastritis, low-grade intraepithelial neoplasia without concurrent GC and high-grade intraepithelial neoplasia (HGIN) without concurrent GC. Ki-67, PCNA and CLDN18.2 expression did not differ by EBV status. In conclusion, EBV infection in GC exhibits a unique spatial pattern, present in neoplastic but not normal epithelium, suggesting it may be a late event rather than a direct etiological driver. This infection pattern provides a rationale for EBV-directed targeted therapies, as the virus could serve as a tumor-specific molecular marker.