ABSTRACT
About 90% of low-grade gastric mucosa-associated lymphoid tissue (MALT) lymphomas are strongly related to Helicobacter pylori infection. The eradication of the H. pylori by antibiotics leads to complete regression of the gastric MALT lymphoma in 80%of cases, and this is currently recommended as the first-line treatment for this tumor. However, no standard treatment for H. pylori-negative and H. pylori-eradication-resistant gastric MALT lymphomas has yet been devised. The association between H. pylori- negative MALT lymphoma and the t(11;18)(q21;q21) translocation, resulting in an API2-MALT1 chimera gene, was reported, and is now considered one of the possible causes of and a reliable predictive marker for unresponsiveness to H. pylori-eradication treatment in patients with low-grade gastric MALT lymphoma. We report a case of H. pylori-eradication-treatment-resistant low-grade gastric MALT lymphoma that was treated successfully with radiotherapy after recognizing the API2-MALT1 chimera gene.