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Helicobacter infection is considered the major predisposing factor for gastric mucosa-associated lymphoid tissue (MALT) lymphoma with initial infection likely occurring in childhood. Primary gastric MALT lymphoma most commonly occurs in patients older than 50 years which is attributed to the lengthy chronic infection time required before the development of MALT lymphoma. Our study analyzes the histologic features and presence of immunoglobulin heavy chain (IGH) clonality in Helicobacter-associated chronic gastritis (62 cases) and Helicobacter-negative chronic gastritis (17 cases) biopsies within the pediatric population, diagnosed between 1996 and 2018. Helicobacter-associated gastritis was more likely to show active inflammation (P=0.01), with no significant difference in number of germinal centers or the strength, linear property, or depth of the inflammatory infiltrate. In total, 47% (29/62) of the Helicobacter-associated cases had at least 1 lymphoepithelial lesion, equivocal or definitive (a modified Wotherspoon score of 3 to 5), compared with 24% (4/17) of the Helicobacter-negative cases (P=0.5). All cases with lymphoepithelial lesions were assessed for IGH clonality, showing the presence of monoclonality in 27% (8/30) of evaluable cases. None of our patients were diagnosed with gastric lymphoma within available follow-up data. Although 4% of our cases could be considered MALT lymphoma in an adult patient based on prominent lymphoepithelial lesions and IGH monoclonality, caution is advised when diagnosing lymphoma in the pediatric population given the good prognosis of Helicobacter-associated gastritis in this age group. It is unclear if these monoclonal lymphoid proliferations require close follow-up.

It has been considered that gastric large B cell lymphoma mainly consists of mucosa-associated lymphoid tissue lymphoma (MALToma) with large cell transformation. However, debate continues about the cell lineage. We analyzed 61 operated cases of gastric B cell lymphoma, mainly focusing on 40 cases of diffuse large cell lymphoma (DLCL). Immunohistologically, two cases were classified as CD10-positive follicular lymphoma, 19 cases were low-grade MALToma, 11 CD10-negative DLCL with a component of low-grade MALToma (high-grade MALToma), 12 CD10-positive DLCL, and 17 CD10-negative DLCL without MALToma (pure DLCL). Lymphoepithelial lesion (LEL) was found in all -cases of high-grade MALToma, and in eight of these its invasion was confined to the mucosa and submucosa. Expression of Bcl-6 was detected in two cases of high-grade MALToma. Only two cases of CD10-positive DLCL had large cell LEL, and seven cases showed tumor invasion beyond the submucosa. All 12 cases were positive for Bcl-6, and a delicate meshwork of CD35 (Ber-MAC-DRC)-positive follicular dendritic cells was detected in eight cases. Pure DLCL of all 17 cases reached the proper muscle layer or more, and expression of Bcl-6 was detected in 10 cases. For patients with pure DLCL, overall survival was significantly (p