Gastric collision tumor of adenocarcinoma and MALT lymphoma: A rare case report and literature review.

Introduction And Importance: Gastric collision tumors, characterized by the coexistence of two distinct malignancies within the same organ, are exceptionally rare. We report a case involving a gastric collision tumor composed of adenocarcinoma (ADK) and marginal zone lymphoma, diagnosed postoperatively. To date, only six cases of MALT lymphoma as part of gastric collision tumors have been published, highlighting the rarity of this association.

Clinical Presentation: A 58-year-old male with type 2 diabetes and a family history of breast cancer presented with six months of anemia and epigastric pain. Endoscopy showed a 5 cm ulcerated, friable gastric mass, and biopsies indicated a low-grade tubular adenocarcinoma. Imaging revealed gastric wall thickening and lymphadenopathy. He received FLOT chemotherapy followed by total gastrectomy with Roux-en-Y reconstruction. Histopathology confirmed a gastric collision tumor with a minimal adenocarcinoma remnant and extensive MALT lymphoma.

Discussion: Collision tumors are rare and present unique diagnostic and therapeutic challenges due to the coexistence of distinct malignancies. This case highlights the complexity of managing such tumors, as accurate diagnosis requires comprehensive histopathological analysis. The dual presence of adenocarcinoma and MALT lymphoma necessitated a tailored approach with FLOT chemotherapy and total gastrectomy. The patient's ongoing adjuvant chemotherapy emphasizes the need for vigilant, long-term follow-up to monitor for recurrence and potential metachronous malignancies.

Conclusion: Gastric collision tumors involving ADK and MALT lymphoma are rare and challenging. This case contributes to the limited literature on collision tumors, highlighting the necessity for comprehensive diagnostic and therapeutic strategies.