EBV-associated gastric carcinoma occurring one year after metabolic bariatric surgery: case report and literature review.

Metabolic bariatric surgery (MBS) does not appear to increase the overall risk of gastric cancer; therefore, there are few documented cases of Epstein-Barr virus-associated gastric carcinoma (EBVaGC) arising early after single anastomosis sleeve ileal bypass (SASI). Here, we report a 62-year-old man who underwent SASI in July 2024 and remained asymptomatic on follow-up. Surveillance endoscopy at 12 months disclosed a 1.2 × 1.0 cm deeply excavated ulcer in the posterior gastric body; biopsy revealed adenocarcinoma with Helicobacter pylori negativity and imaging showed focal wall thickening. Indocyanine green-guided laparoscopic radical gastrectomy demonstrated moderately to poorly differentiated EBVaGC with diffuse EBER in situ hybridization positivity, preserved mismatch repair protein expression, wild-type p53, and a high proliferative index (Ki-67 ~90%). Targeted sequencing identified an ARID1A truncating mutation (p.Y215*, VAF 4.56%) and CCND1 amplification (~6 copies). Plasma EBV and postoperative circulating tumor DNA minimal residual disease testing were negative (single ATR VUS at 0.10%). The patient recovered uneventfully and remained disease-free at 8 months. This case highlights the biologic plausibility of tissue EBV positivity despite negative plasma EBV in EBVaGC and supports a post-MBS evaluation strategy that incorporates EBER-ISH and molecular stratification for suspicious gastric lesions, with a lower threshold for diagnostic endoscopy in patients with persistent upper gastrointestinal symptoms or unexplained nutritional abnormalities; routine gastroscopic assessment at approximately 1 year after MBS may also be considered to evaluate remnant gastric mucosal health.