| Abstract: | A 60‐year‐old man underwent routine colonoscopy, and was noted to have a pedunculated polyp in the sigmoid colon. The pathologic diagnosis was adenoma, and due to patient’s personal circumstances, the lesion was left untreated. The colonoscopic examination was repeated 4 years and 11 months later, to find that the polyp had transformed into an elevated lesion with irregularly depressed surface. The patient was diagnosed as having early sigmoid cancer, and underwent sigmoidectomy. The histologic examination of the excised specimen revealed well‐differentiated adenocarcinoma with invasion into the submucosal layer. Through studying the natural course of colon cancer, it has become known that the advanced cancers commonly develop from polyps with short pedicles (sessile polyps). This case represents an early sigmoid cancer developed from a pedunculated polyp, which differs from the current mainstream concept of ‘polyp‐cancer sequence of colon cancer.’ |
