大腸腺腫・M癌の内視鏡的切除後のfollow up：サーベイランスに向けて―内視鏡追跡例からみた小さな大腸腺腫の自然史：リスク別サーベイランスのあり方

Natural History of the Small Colorectal Adenomas―Optimal Surveillance Regarding the Risk Factor

要旨　小さな大腸腺腫の取り扱いについてのコンセンサスはわが国では得られておらず，組織学的変化や内視鏡にて長期経過観察された報告はほとんどない．今回，初回生検にて軽度もしくは中等度異型腺腫と診断された腫瘍径10mm未満の隆起型および表面隆起型腺腫332症例408病変に対する内視鏡的追跡（平均観察期間43.1か月）による発育進展の検討を行い，大腸腺腫の自然史からみた至適サーベイランスについて考察した．408病変のうち形態変化を来したものは22病変5.4％，3mm以上の腫瘍径増大を認めたものは35病変8.6％，最終腫瘍径が10mm以上となったものは12病変2.9％であった．粘膜内癌へ発育進展したものは3病変0.7％で，全例に3個以上の腺腫が併存し，腫瘍の大腸内視鏡治療歴があり，かつ10mm以上の腫瘍性病変の既往があった．組織学的および内視鏡的に追跡した小さな大腸腺腫の自然史の検討からは，リスクを有する症例であっても5年間は重大な病変への変化を認めることはなかったが，5年以降では腫瘍は増大し，悪性化するものがあった．以上から，個別のリスクがサーベイランスのあり方に影響する可能性はあるが，小さな腺腫は5年後のサーベイランスで対処可能と結論された．

　There is still no consensus regarding the handling of small colorectal adenomas, and there have been hardly any reports in which long-term follow-up has been performed on the basis of histological changes or endoscopic findings. In this study we assessed the development and progression by endoscopic follow-up for a mean period of 43.1 months of 408 lesions in 332 cases of elevated type or superficial elevated type tumors under 10 mm in diameter diagnosed as adenomas with mild or moderate atypia on the basis of the initial biopsy, and we discuss optimal surveillance from the standpoint of the natural history of colorectal adenomas.

　Of the 408 lesions 22 (5.4％) underwent morphological changes. An increase in tumor diameter of 3mm or more was observed in 35 lesions (8.6％). There were 12 lesions (2.9％) whose final tumor diameter had reached 10mm or more. There were 3 lesions (0.7％) that developed and progressed into intramucosal cancer. In all 3 of those cases there were multiple simultaneous adenomas. These patients had a history of colorectal endoscopic treatment, and there were simultaneous adenomas over 10mm in diameter. Based on our assessment of the natural history of small colorectal adenomas followed up histologically and endoscopically, no changes toward major lesions were observed for at least 5 years. However, from 5 years onward some tumors increased in size and became malignant.