Japanese Society of Internal Medicine Acta Medica Okayama 0918-2918 63 12 2024 Gastric Mucosa-associated Lymphoid Tissue Lymphoma That Relapsed after 11 Years Subsequent to Achieving Complete Remission 1697 1702 EN Shoko Inoo Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences Masaya Iwamuro Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences Takehiro Tanaka Department of Pathology, Okayama University Hospital Yoshiro Kawahara Department of Practical Gastrointestinal Endoscopy, Okayama University Hospital Motoyuki Ootuka Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences A 38-year-old Japanese man was diagnosed with extranodal marginal zone lymphoma of the mucosa-associated lymphoid tissue in the stomach (gastric MALT lymphoma). Fluorescence in situ hybridization analysis revealed the absence of t (11;18) (q21;q21) translocation but the presence of extra copies of MALT1, indicating tetrasomy 18. Helicobacter pylori eradication led to complete remission (CR). However, the gastric MALT lymphoma relapsed after 11 years old. This case underscores the need for long-term observation (>10 years) of patients with gastric MALT lymphoma. Further investigation is warranted to elucidate the correlation between trisomy/tetrasomy 18 and the recurrence propensity. No potential conflict of interest relevant to this article was reported.