2021 Volume 24 Issue 1 Pages 49-62
Gastric mucosa-associated lymphoid tissue (MALT) lymphoma, which is included in the low-grade B-cell lymphoma category, comprises 40% of lymphomas that develop in the stomach. Patients may present with non-specific gastrointestinal symptoms, such as epigastric discomfort or nausea, or the disease may be incidentally detected by an upper gastrointestinal series performed as a part of a preventative medical examination. Under endoscopy, the appearance of gastric MALT lymphoma varies, including multiple erosions or ulcers, cobblestone-like mucosa, IIc-type early gastric cancer, or protruding tumor. Lymphoma cells are small to medium in size with centrocyte-like morphology, and infiltrate into and proliferate in the lamina propria of gastric mucosa. The cells are positive for CD20, CD79a, and BCL2, and negative for CD5, CD10, CD23, BCL6, and cyclin D1. Six to 26% of patients have t(11;18)(q21;q21)/API2-MALT1 translocation, which is detected by fluorescence in situ hybridization using biopsy specimens. Around 80% of patients have early-stage disease categorized as stage I or II1 by the Lugano staging scheme. The prevalence of Helicobacter pylori infection in Japanese patients is 90%. The infection is detected either by endoscopy-based or non-invasive tests. H. pylori eradication therapy is the treatment of choice for patients with H. pylori-positive early-stage disease. H. pylori infection is eliminated at a rate between 67.5 and 92.6% by first-line eradication therapy, and between 83.9 and 98.0% by second-line therapy. The overall response rate of gastric MALT lymphoma ranges between 50 and 80% based on Wotherspoon or GELA histopathological criteria. Many clinical studies revealed t(11;18)/API2-MALT1 to be a biomarker predicting treatment resistance. For eradication treatment-refractory and H. pylori-negative patients, low- to medium-dose radiotherapy is performed. Patients with advance-stage disease, i.e., Lugano stage II2 or higher or Ann Arbor stage III or higher, receive single-agent rituximab or rituximab plus cytotoxic drugs. However, the watchful waiting policy may be feasible for patients with asymptomatic disease or those with a low tumor burden.
