大腸serrated adenomaの内視鏡的検討―臨床診断は可能か？

Colorectal Serrated Adenomas: Endoscopic Findings

要旨　過去7年間に当院で内視鏡的に切除され，組織学的にserrated adenoma（SA）と診断された63例，64病変の肉眼所見を中心に検討した．SAは直腸，S状結腸に多く分布し，大きさは5mm以上，不規則あるいは分葉・結節状の表面構造で，赤色調の病変が多い傾向であったが，特異的な所見はなかった．一方，64病変中，8病変12.5％に癌の合併を認め，化生性ポリープ（MP），SAの相方の成分を認める病変もあり，MPからSAを介するadenoma-carcinoma sequenceが示唆され，SAは，内視鏡的治療の適応となる病変と考えられた．

　Serrated adenoma is a distinct form of adenoma. It is characterized by a serrated epithelium resembling a metaplastic polyp. The present study shows the endoscopic findings in 64 colorectal serrated adenomas detected in 63 patients. 41 adenomas (64.1%) were located in the sigmoid colon and rectum. Twenty-one adenomas (32.8%) were in the right side colon. Sixteen of the serrated adenomas were pedunculated, 22 were subpedunculated, 16 were sessile, six were flat. The mean size of the adenomas was 9.2 mm (range 4～32 mm). Thirty-five adenomas (54.7%) were between 5 to 9 mm in diameter. Eight in 15 adenomas larger than 15 mm were the pedunculated polyp type. The adenomas tend to be reddish in color and to have a nodular surface, and especially to be larger in size.

　Eight adenomas (12.5%) had the component of intra-mucosal carcinoma. The mean size of the lesions was 13.9 mm (range 6～24 mm). There are serrated adenomas with both a metaplastic element and a carcinoma element. It suggest a metaplastic-adenoma-carcinoma sequence. Serrated adenoma should be removed endoscopically in the same manner as tubular adenomas.