An 84-year-old man was monitored after resection of descending colon cancer. During follow-up, colonoscopy showed a flat elevated lesion, 8 mm in size, in the lower rectum. The lesion was slightly reddish and had dilated vessels with branch architecture on the surface. Follow-up colonoscopy performed 10 months later showed that the lesion had progressed to the lateral side and increased to 15 mm. Dilated vessels with branch architecture were further emphasized by magnifying endoscopy with NBI. Biopsy specimens showed MALT lymphoma. Image findings and bone marrow biopsy were negative. We performed an ESD. Immunohistochemically, the lesion was confirmed to be MALT lymphoma. We reported a case of MALT lymphoma that could be observed at an early developmental stage by endoscopy.
