Case Report: Synchronous minute intramucosal Epstein-Barr virus-associated gastric cancer revealed after short-term Helicobacter pylori eradication.

Epstein-Barr virus-associated gastric cancer (EBVaGC) is a rare subtype, accounting for approximately 8.7% of gastric cancers worldwide. It predominantly affects males and typically presents endoscopically as a superficial depressed lesion or with a submucosal tumor-like appearance. Pathologically, it is characterized by prominent lymphoid stromal infiltration (gastric carcinoma with lymphoid stroma, GCLS). Molecular features include extensive CpG island methylation, PIK3CA mutations, and high PD-L1/PD-L2 expression. We report the case of a 56-year-old patient diagnosed with gastric adenocarcinoma at an outside institution. Upon admission, magnifying endoscopy with narrow-band imaging (ME-NBI) revealed active Helicobacter pylori (HP) infection and a Paris 0-IIc reddish lesion on the posterior wall of the middle gastric body with indistinct margins. The patient underwent a 2-week HP eradication regimen. Subsequent endoscopic submucosal dissection (ESD) revealed two distinct superficial depressed lesions, which were removed en bloc. The lesions measured 15 mm (distal lesion) and 26 mm (proximal lesion), respectively. Postoperative pathology confirmed two independent foci of intramucosal EBVaGC with positive EBER in situ hybridization. The lesions were limited to the mucosa (pTis) without lymphovascular invasion, achieving curative resection (eCura A). At the 6-month follow-up, no recurrence was observed. This case suggests that in the setting of active HP-associated gastritis, EBVaGC may be obscured; Short-term preoperative HP eradication may alleviate background inflammation, potentially improving the detection of minute lesions and the delineation of margins. These findings form a hypothesis that eradication might aid endoscopic assessment, which requires validation in larger cohorts. Under strict risk assessment and margin control, ESD represents a curative modality for early EBVaGC.