Analysis of malignant biology and gene disorder in gastric MALT lymphomas

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Since new entity of low-grade B-cell lymphoma of mucosa associated lymphoid tissue (MALT) was established, re-evaluation of gastric lymphoma was carried on and optimal treatment protocol of MALT lymphoma has been anticipated. Consecutive 40 surgical cases of gastric B-cell lymphoma were histopathologically reclassified as MALT lymphoma (n=26 ; 18 low-grade and 8 high-grade) and non-MALT lymphoma (n=14), analyzed clinicopathologically including prognosis, and comparatively investigated between two groups. Compared to non-MALT lymphomas, patients of MALT lymphoma often presented no symptoms or vague symptoms with longer history and better prognosis after surgery irrespective of high-grade transformation, lymph node involvement or postoperative chemotherapy. MALT lymphomas exhibited larger extent, superficial spread of the mucosa and submucosa, and evasive margins of the tumor until scrutinized histology. 5-yr survival rate of patients with MALT lymphoma was 94%, significantly higher than 59% of non-MALT lymphoma. However, no significant difference was obtained between 64% of high-grade MALT lymphoma and 59% of non-MALT lymphoma. Gastric MALT lymphomas should be biologically different from conventional non-MALT lymphomas, leading to the optimal surgical treatment of total gastrectomy with level 2 lymph node dissection so far. Newly investigated pathogenesis of MALT lymphoma by Helicobacter Pylori infection would consequently take the clinical transitions of treatment protocol in the future.