大腸鋸歯状病変に対する内視鏡診断の進歩

Endoscopic Detection and Diagnosis of Serrated Lesions of the Colon

要旨●大腸鋸歯状病変はかつて非腫瘍性病変とされたが，現在はmalignant potentialを有する病変と扱われるようになった．大腸鋸歯状病変の検出率向上には，NBI/TXI/LCIなどの画像強調観察やCADeだけでなく，ポスター掲示やFIND 4 key cluesなどの教育も有用である．観察においては，各病変の典型像・特徴的な所見を病理像とともに学ぶ必要がある一方，大腸鋸歯状病変がserrated pathwayの中を多彩に発育していく概念をもつことも重要である．また，内視鏡観察によるHPとSSLの正確な鑑別診断は困難とされ，内視鏡的に指摘困難なSSLDや癌化症例も報告されている．大腸鋸歯状病変の診断には，各病変の理解だけでなく，serrated pathwayを俯瞰した視野と自身の診断を過信しない謙虚さが求められる．

　Colorectal serrated lesions, which were previously considered nonneoplastic, are now considered to have malignant potential. To increase the detection rate of sessile serrated lesions, we recommend using not only image-enhanced endoscopic techniques such as NBI（narrow band imaging）, TXI（texture and color enhancement imaging）, and LCI（linked color imaging）but also CADe（computer-aided detection）, educational initiatives such as posters, and programs such as the FIND 4 key clues.

　For diagnostic purposes, it is necessary to learn the endoscopic and pathological features of each serrated lesion ; however, even experts find it difficult to accurately differentiate endoscopically between hyperplastic polyps and sessile serrated lesions. The diagnosis of colorectal serrated lesions requires not only an understanding of individual lesions but also a comprehensive perspective of the serrated pathway, coupled with the humility needed to avoid overconfidence in one's diagnostic capabilities.