A case of early colonic cancer associated with a sessile serrated lesion in the ascending colon

A 57-year-old man, who was administered methotrexate for rheumatoid arthritis seven years prior, experienced lower abdominal pain and diarrhea for one year; therefore, he visited our hospital for further examination. Colonoscopic examination revealed an Is-type polyp in the anal side of the ileocecal valve and Is-like elevated lesion in the ascending colon, which were then removed endoscopically. Narrow-band imaging revealed a type II open pit pattern like in the center of the lesion and a type VN pit pattern like in the periphery of the lesion. The former histopathological findings indicated low-grade tubular adenoma; the latter indicated early colonic cancer with submucosal invasion in the peripheral lesion and a hyperplastic polyp with a serrated pattern in the center of the lesion in the ascending colon. He is currently undergoing regular follow-up.