We report the case of a 74-year-old man with mantle cell lymphoma, who was referred to our hospital for further investigation of multiple gastric submucosal tumors. Esophagogastroduodenoscopy (EGD) showed tonsillar enlargement, submucosal tumors measuring under a few mm in diameter in the esophagus, and submucosal tumors measuring less than 20 mm in diameter in the stomach. Trans-anal single-balloon endoscopy revealed multiple lymphomatous polyposis in the lower ileum, colon and rectum. Immunohistological staining of the gastric biopsy specimen showed positive staining for CD5 and CyclinD1, which was compatible with the diagnosis of mantle cell lymphoma (MCL) . Thus, we encountered a case of MCL with GI involvement, which could be successfully evaluated by EGD and single-balloon enteroscopy.
