452 EBER-Positive Intramucosal Carcinoma Arising in Gastric Foveolar Dysplasia Without Intestinal Metaplasia: A Rare Case Expanding EBV-Driven Tumorigenesis

Introduction/Objective Epstein-Barr virus-associated gastric carcinoma (EBVaGC) typically arises in intestinalized mucosa, with EBV infection considered a late event. Its role in precursor lesions remains poorly understood. Methods/Case Report An 82-year-old male with remote Billroth II surgery underwent endoscopic evaluation for a pancreatic mass. Incidentally, a 25 mm gastric body lesion was identified and resected by endoscopic submucosal dissection. Histology revealed foveolar-type dysplasia and adjacent intramucosal adenocarcinoma. Both components were strongly EBV-positive by EBER in situ hybridization (EBER-ISH). The dysplasia showed MUC5AC positivity with a gastric phenotype (CK7 patchy, CDX2−), while the carcinoma exhibited loss of MUC5AC and increased p53 expression with a wild-type pattern. Background mucosa lacked intestinal metaplasia, Helicobacter pylori, and enterochromaffin-like cell hyperplasia, consistent with post-surgical atrophic body-type mucosa. Results NA Conclusion This case demonstrates EBV-positive foveolar-type dysplasia progressing to carcinoma in non-metaplastic gastric mucosa, challenging the conventional sequence of EBVaGC development. The findings support EBV as an early and sufficient oncogenic driver, independent of intestinal metaplasia or H. pylori, and highlight an underrecognized gastric pathway. Awareness of this alternate route may impact diagnostic classification, early detection, and surveillance strategies.