Complete remission of Helicobacter pylori-negative gastric MALT lymphoma following eradication therapy

Rationale: Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is typically associated with Helicobacter pylori infection; however, approximately 10% of cases are H pylori -negative. Management guidelines differ between the European Society for Medical Oncology (ESMO) and the National Comprehensive Cancer Network (NCCN) regarding first-line treatment for these patients. Here, we report a case of H pylori -negative gastric MALT lymphoma that achieved complete remission following standard eradication therapy. Patient concerns: A woman of Asian ethnicity in her late 50s presented with a 4-month history of intermittent, left-upper-quadrant abdominal pain. The patient had no significant medical or family history of gastric cancer or lymphoma. Diagnoses: Upper gastrointestinal endoscopy revealed irregular whitish mucosa with ill-defined borders in the distal gastric body. Biopsies demonstrated dense lymphoid infiltrates positive for CD20, CD79a, CD43, kappa light chain, focal CD23, and CD21, with a Ki-67 index of approximately 8%, consistent with extranodal marginal zone lymphoma (MALT lymphoma). H pylori testing by 13 C-urea breath test (DOB 3.5; cutoff < 4.0) and Giemsa staining was negative, although the DOB value was close to the cutoff threshold. Positron emission tomography-computed tomography and endoscopic ultrasound confirmed Lugano stage IE disease confined to the mucosa and submucosa. Interventions: After multidisciplinary consultation, the patient received a 14-day bismuth-containing quadruple eradication regimen consisting of bismuth potassium citrate (2.4 g) twice daily, esomeprazole (40 mg) twice daily, amoxicillin (1 g) twice daily, and clarithromycin (0.5 g) twice daily. Outcomes: At 2-month follow-up, the patient was asymptomatic. Positron emission tomography-computed tomography showed no abnormalities, and repeat endoscopy with biopsies demonstrated complete histological remission, which persisted at 6-month follow-up. Lessons: This case adds to the growing evidence that H pylori status alone should not preclude a trial of eradication therapy in patients with localized gastric MALT lymphoma. Potential mechanisms include the role of non- H pylori helicobacters, the direct antitumor effects of antibiotics, and immunomodulation. Larger prospective studies are needed to identify predictors of response in this population.