Endoscopic submucosal dissection in Helicobacter pylori-negative early gastric adenocarcinoma with diffuse large B-cell lymphoma: a two-case report and literature review.

We describe two rare cases of synchronous early gastric adenocarcinoma (EGA) and diffuse large B-cell lymphoma (DLBCL) involving the stomach and colon in Helicobacter pylori-negative patients. Case 1: A 61-year-old male presenting with abdominal pain was diagnosed with synchronous EGA and colonic DLBCL via endoscopy. Following 8 cycles of R-CDOP chemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone). The patient subsequently underwent endoscopic submucosal dissection (ESD) for EGA without gastrectomy. Case 2: A 67-year-old male with a history of gastric DLBCL (treated with 9 cycles of R-CDOP within 6 months) was diagnosed with EGA on surveillance gastroscopy and managed with ESD. Both patients achieved complete resection and remained disease-free at 16-month follow-up. These cases highlight the feasibility of ESD as a curative option for Helicobacter pylori-negative EGA coexisting with DLBCL.