Low-grade gastric B-cell lymphoma of mucosa-associated lymphoid tissue: clinicopathologic analysis of 19 cases.

Low-grade gastric B-cell lymphoma of mucosa-associated lymphoid tissue type (MALToma) is a recently recognized disease entity. We report the clinicopathologic features of 19 patients with MALToma in Taiwan. The 19 patients included eight men and 11 women, ranging in age from 26 to 77 years, with a mean age of 58.8 years. Most complained of abdominal pain or gastrointestinal bleeding. The endoscopic and gross features of the gastric lesions revealed erosion (flat type), ulceration (depressed type), cobblestone appearance or abnormal gastric folds (elevated type), mimicking chronic gastritis, ulcer or early gastric carcinoma. Typical histopathologic features included lymphoepithelial lesion and extensive mucosal infiltration of centrocyte-like cells in all cases. Clonality analysis of the variable-diversity-joining region of the immunoglobulin gene by semi-nested polymerase chain reaction demonstrated monoclonality in 72% of the cases. Helicobacter pylori bacilli (H. pylori) could be identified on histologic sections in 15 cases (78.9%); the serologic test for H. pylori was positive in 12 of 13 patients tested (92%). In six patients receiving triple therapy (amoxicillin, bismuth subcitrate and metronidazole), five showed significant histologic regression with eradication of H. pylori 4 to 6 months after the start of treatment; one patient showed persistent lesions and presence of H. pylori. However, persistence of residual lymphoid cells and monoclonality of the immunoglobulin gene, could still be demonstrated in four cases. Of nine patients treated with surgery or chemotherapy, two died: one due to concomitant gastric carcinoma and the other one due to sudden apnea. No recurrence was observed in the remaining seven patients. The remaining four patients were lost to follow-up. Our experience confirmed that gastric MALToma is a low-grade neoplastic process. The dramatic response of gastric MALToma to anti-H. pylori treatment suggests that H. pylori infection is closely related to the pathogenesis of low-grade gastric MALToma. However, long-term follow-up is mandatory due to the persistence of the monoclonality of the immunoglobulin gene in the residual lymphoid cells after treatment.