Gastric adenocarcinoma is a common malignant tumor of the digestive system. Primary diffuse large B-cell lymphoma (DLBCL) of the stomach is a common lymphoma originating from gastric submucosal lymphoid tissue, and the coexistence of DLBCL and adenocarcinoma is exceedingly rare. A 58-year-old woman came to our hospital for treatment because of a choking feeling after eating. During endoscopy, it was confirmed that multiple irregular ulcers were seen in the fundus and body of the stomach, and the surrounding mucosa was raised. The biopsy pathology showed poorly differentiated cancer, and the patient did not undergo immunohistochemical detection. A distal gastrectomy was performed. Pathological evaluation of resected specimens is as follows: gastric tubular adenocarcinoma and germinal center-type (GC)-DLBCL. No migration was found at the junction of the two tumors, forming a collision tumor. The patient received two cycles of Rituximab - Cyclophosphamide, doxorubicin, vincristine, prednisone (R-CHOP) chemotherapy, and there is no recurrence at present. We report a case of primary gastric adenocarcinoma colliding with the GC-DLBCL. Clinicians and pathologists should pay attention to it to avoid missed diagnosis.
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