Concurrent Adenocarcinoma and Mucosa-Associated Lymphoid Tissue Lymphoma of the Stomach: A Case Report and Narrative Literature Review.

INTRODUCTION: The synchronous presentation of two distinct primary malignancies in the stomach, specifically gastric adenocarcinoma (GAC) and mucosa-associated lymphoid tissue (MALT) lymphoma, is an extremely rare clinical entity. These dual primary tumors challenge standard management protocols due to their differing biologies. CASE PRESENTATION: We present a case of a patient diagnosed with concurrent GAC and MALT lymphoma who was also found to have a pulmonary nodule, creating a complex staging dilemma. Surgical pathology revealed distinct neoplastic entities: gastroesophageal junction adenocarcinoma, gastric MALT lymphoma, and a pulmonary hamartoma. We provide a narrative review of selected cases from the literature to contextualize this finding. CONCLUSION: Our observations suggest that in such complex presentations, the prognosis is often driven by the higher-grade malignancy, necessitating a multidisciplinary approach to distinguish between metastatic disease and synchronous benign or indolent lesions.