Primary extranodal marginal zone lymphoma of gastric mucosa-associated lymphoid tissue in children: a case report and review of the literature

Abstract Background Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue represents an important subtype of marginal zone lymphoma, a heterogeneous B-cell neoplasm originating from the marginal zone of lymphoid follicles. Therefore, gastric marginal zone lymphoma arising from mucosa-associated lymphoid tissue in immunocompetent children is particularly special. This article aims to report this rare case and systematically review the research progress of pediatric marginal zone lymphoma combined with its clinicopathological features. Case presentation A 13-year-old Chinese female presented with a 3-month history of recurrent epigastric pain. Gastroscopy revealed multiple ulcers in the gastric angle and antrum. Histopathological examination identified lymphoepithelial lesions and lymphoid infiltration. Immunohistochemistry showed positivity for CD20 and CD79a and negativity for CD3. PCR and capillary electrophoresis detected clonal immunoglobulin gene rearrangements, confirming monoclonality. These findings supported the diagnosis of gastric mucosa‑associated lymphoid tissue lymphoma. [ 68 Ga]Pentixafor-PET showed multiregional involvement, and Lugano stage IV was suspected (based on imaging alone, as histopathological confirmation was declined by the family). Fortunately, the patient's gastric lesions are now resolved without any discomfort after Helicobacter pylori eradication therapy. Nearly 12 months later, the patient remains on follow-up and is currently asymptomatic. Conclusions This case describes a Chinese child with pediatric gastric mucosa‑associated lymphoid tissue lymphoma with PET‑defined stage IV disease that was clearly associated with Helicobacter pylori infection. The patient achieved clinical and endoscopic remission with eradication therapy. These findings suggest that even when imaging indicates possible distant involvement, some children may still benefit from conservative treatment targeting the infection source, thereby avoiding more aggressive initial therapy (such as chemotherapy) and expanding clinical management options for such rare cases.