大腸鋸歯状病変の内視鏡診断

Endoscopic Diagnosis of Serrated Adenoma Using Magnifying Endoscopy

要旨　過去7年間に当センターにて経験したserrated adenomaの臨床的特徴および内視鏡所見について検討した．同期間に12,302病変に対して内視鏡切除が施行され，病理組織学的に95病変（0.77％）がserrated adenomaであった．男女比は1.26で，全95病変中56病変（58.9％）が直腸，S状結腸に存在し，隆起型病変が81病変（85.3％）を占めていた．拡大観察による検討ではIII_H型pitの一致率が26.8％，IV_H型pitの一致率は50.0％であった．また，SAの担癌率は9.5％であった．現時点での臨床的取り扱いは，腺腫に準じた取り扱いで差し支えないものと考えられる．

　Serrated adenoma (SA) is a distinct form of adenoma. It is characterized by a serrated epithelium resembling a metaplastic polyp. A total of 12,302 lesions were removed endoscopically at this clinic from January, 1999 to December, 2005. The present study shows the endoscopic findings in 95 colorectal serrated adenomas detected in 79 patients. Among these lesions, 56 (58.9％) lesions were located in the sigmoid colon and rectum. Eighty-one lesions (85.3％) were protruded type, 14 (14.7％) were superficial type. The mean size of SAs was 13.3 mm (range 3～45 mm). Thirty-nine SAs (41.1％) were between 6 to 10 mm in diameter. Nine (9.5％) of all SAs had the component of intramucosal carcinoma. This suggests that SA should be removed endoscopically in the same manner as tubular adenomas.

　Magnifying endoscopic assessment was obtained in 93 SAs (97.9 ％). The diagnostic accuracy for IV_H pit pattern for serrated adenomas by magnifying colonoscopy was 50.0％. The accuracy for III_H pit pattern with IV_H or IV pit pattern was 38.1 ％. The diagnostic accuracy for III_H pit pattern was not satisfactory (26.8 ％). In the present study, the accuracy rate of the IV_H pit pattern was high, so we suggest that the IV_H pit pattern is useful for differentiating serrated adenomas by magnifying colonoscopy, especially in the protruded SAs. Although an endoscopic pit pattern classification for the diagnosis of serrated adenoma has not been established, magnifying endoscopy is expected to become a key diagnostic method for discrimination between serrated adenoma and other polyps.