High-grade B-cell lymphoma arising in mucosa-associated lymphoid tissue of the duodenum.

Duodenal mucosa-associated lymphoid tissue lymphoma is a rare neoplasm. We report a case of a 70-year-old man with non-Hodgkin's lymphoma located in the descending duodenum that was not associated with Helicobacter pylori infection of the stomach. A surgical resection due to obstruction of the bowel lumen above the ligament of Treitz was performed. No invasion into the adjacent structure was confirmed at surgery. The pathological examination showed an infiltration of the duodenal mucosa and submucosa with B lymphocytes. Monoclonal proliferation of the lymphoid tissue was demonstrated by polymerase chain reaction. The histological appearance and the demonstration of monoclonality fulfilled the criteria for malignant high-grade B-cell lymphoma arising from mucosa-associated lymphoid tissue.