Supplementary Material for: <i>Helicobacter pylori</i>-Negative Gastric Mucosa-Associated Lymphoid Tissue Lymphoma in a Girl

<b><i>Introduction:</i></b> Extranodal marginal zone lymphoma (MZL) arises in a number of epithelial tissues, including the stomach, salivary gland, lung, small bowel, thyroid, ocular adnexa, skin, and elsewhere. It has also been called low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT). MALT lymphoma predominantly occurs in adults and is rare in children. <b><i>Case Presentation:</i></b> We report a case of MALT lymphoma involving the stomach, which is the most common subtype, in a 12-year-old girl. Initially, the patient relapsed after antibiotic therapy but achieved successful treatment subsequently through irradiation. <b><i>Conclusion:</i></b> <i>Helicobacter pylori</i> eradication therapy should be given to all patients with gastric MZL, irrespective of stage. In patients who do not respond to antibiotic therapy, treatment options such as irradiation and systemic cancer therapies should be considered, depending on the disease stage.