**Background:** Extranodal marginal zone B-cell lymphoma (EMZBL) of mucosa-associated lymphoid tissue (MALT) is extremely rare in children, as it typically arises from decades of chronic inflammation, most commonly due to Helicobacter pylori infection. H. pylori infects about half the world's population, but less than 0.5% develop MALT lymphoma. In children, H. pylori prevalence varies (up to 55% in developing countries) and increases with age. This case highlights the youngest reported patient with gastric MALT lymphoma and underscores the diagnostic value of upper gastrointestinal endoscopy in children with persistent upper GI symptoms.
**Methods:** This is a single case report from the Security Forces Hospital. A previously healthy 9-year-old girl presented with a 3-month history of increasingly severe epigastric pain, nausea, weight loss (3 kg), decreased appetite and energy, irregular bowel movements, and black stools with blood clots. Physical exam revealed an ill, thin, pale child weighing 19.5 kg with epigastric tenderness. Laboratory tests showed: hemoglobin 72 g/L (normal 110–160), MCV 63 fL (77–98), platelets 684 × 10^9/L (150–400), C-reactive protein 183 mg/L (<5), ESR 43 mm/hour (0–20), albumin 24 g/L (38–40), LDH 254 g/L (120–300), positive occult blood, and positive stool H. pylori. Gastroduodenoscopy revealed an ulcerated gastric mass with irregular surface occupying most of the fundus and body, with significant antral nodularity. H. pylori urease test was positive. Multiple biopsies (gastric mapping) showed lymphoepithelial lesions; immunohistochemistry was positive for CD20 and CD43, negative for CD10 and CD5. Antral biopsies showed active chronic H. pylori gastritis. CT scans of chest, abdomen, and pelvis showed extensive diffuse gastric wall thickening (fundus, body, antrum) and multiple enlarged mesenteric lymph nodes at the lesser sac.
**Key Results:** The patient received H. pylori eradication therapy (amoxicillin, clarithromycin, proton pump inhibitor) for 2 weeks. One week post-treatment, repeat gastroscopy showed no change in the mass, and H. pylori was not detected in biopsies. Due to advanced stage, she was referred to oncology and received 6 cycles of chemotherapy (rituximab plus cyclophosphamide, doxorubicin, vincristine, prednisone) over 6 months. After chemotherapy, gastroscopy with multiple biopsies showed complete remission. Three months later, repeat gastroscopy and biopsies showed no relapse. Subsequent gastroscopies every 6 months for 2 years showed no recurrence.
**Clinical Implications:** This case demonstrates that gastric MALT lymphoma can occur in very young children, contrary to the typical decades-long latency. The patient's advanced stage at presentation (stage III/IV) with significant symptoms (weight loss, anemia, melena) underscores the need for early endoscopy in children with persistent epigastric pain, weight loss, and alarm symptoms. Despite advanced disease, the prognosis was excellent with combined H. pylori eradication and chemotherapy, consistent with reported excellent outcomes in pediatric EMZBL. The case also highlights the importance of adequate biopsy sampling (gastric mapping) for diagnosis and the need for H. pylori eradication in all stages, with chemotherapy for non-responsive or advanced disease. The authors note that clarithromycin resistance is increasing, and metronidazole-based regimens may be preferred as first-line therapy per ESPGHAN/NASPGHAN guidelines, though culture and susceptibility testing were not available.