A man in his 70s underwent colonoscopy due to annual follow-up after rectal cancer surgery. Colonoscopy revealed multiple elevated lesions of various sizes and forms in the descending colon and rectum. Magnifying endoscopy with narrow band imaging showed abnormal microvessels with a variable caliber on the surface of the polyps, and white opaque spots under the microvessels. Crystal violet staining demonstrated round pits showing type I pit pattern. Based on the pathological examination involving immunohistochemical staining, the colorectal tumor was diagnosed as follicular lymphoma (FL). No lymphoma invasion was found in other organs. We diagnosed the primary colorectal FL as clinical stage I according to the Lugano classification, and followed-up by watch and wait therapy.
There are few reports of colorectal FL and its diagnosis and treatment policy have not been clarified yet. In addition, there are few reports on the endoscopic findings. We here present a case of primary colorectal FL in which detailed endoscopic examination was possible.
