Gastrointestinal involvement by mantle cell lymphoma identified by biopsy performed during endoscopy: A case report.

Rationale: Primary gastrointestinal mantle cell lymphoma is rare, and histopathological examination and specific immunohistochemical staining are still the gold standard for diagnosis. Therefore, it is necessary to find a new way to improve positive biopsy rates.

Patient Concerns: A 58-year-old man was admitted to our hospital with epigastric pain, abdominal distension, nausea, and melena.