切開・剥離法（ESD）に必要な胃癌術前診断―内視鏡診断―側方進展診断を中心に―酢酸・拡大観察を含めて

Endoscopic Diagnosis of Early Gastric Cancer―Magnifying Endoscopy and Acetic Acid Spreading

要旨　ESDにて一括切除したにもかかわらず側方断端が陽性になる原因は側方進展範囲診断の誤り，または同時多発癌の見落としである．これらを予防するには術前の内視鏡診断が極めて重要となる．ESDの適応となる分化型粘膜内癌は腸上皮化生内に発生することが多く，周囲粘膜の萎縮が強い場合は癌の境界が極めて不明瞭となる．従来の内視鏡診断学では色調変化，表面性状，段差に注目して診断を進めてきたが，色調や表面構造の変化が少ない癌ではその進展範囲診断は困難であった．これらに対して近年では拡大内視鏡による血管構造の解析や1.5％酢酸撒布による色調の変化，また酢酸撒布後の拡大観察にてpit patternを解析する新たな内視鏡診断学が構築されつつある．本稿ではこれらの新たな内視鏡診断法が有用であった症例を呈示した．

　A precise large resection is able to be performed, using endoscopic submucosal dissection (ESD). However, sometimes the lateral margin of the resected specimens are diagnosed as positive. There are two reasons for this ; one is the misdiagnosis of the lateral extension and the other is the oversight of an adjoining second lesion.

　Pre-medication with pronase is very important for a precise diagnosis because, if there is mucus on the lesion, it might be difficult to observe the lesion clearly. In〔case 1〕, pre-medication was poor so the lateral extension could not be diagnosed (Fig. 1, 2). However, the margin of the lesion was able to be diagnosed clearly after pronase pre-medication (Fig. 3, 4). Sometimes, there are flat lesions with unclear margins. Magnifying endoscopy is useful to diagnose the lateral margin of such lesions (Fig. 6-9). And in〔case 2〕, there was a synchronous second cancer near the main cancer. However, the diagnosis of the second lesion was impossible with conventional endoscopy (Fig. 12-14). Magnifying endoscopy revealed a flat small lesion with irregular vessels. Therefore, we were able to diagnose this small lesion as a minute synchronous adenocarcinoma. If the second lesion was not diagnosed, ESD would be carried out for the main lesion and the lateral margin would be positive because of the oversight second lesion. In〔case 4〕, a shallow depressed lesion with unclear margin became clearer after 1.5 ％ acetic acid spreading (Fig. 21).

　The precise diagnosis of lateral extension is very important for en bloc resection by ESD. Magnifying endoscopy and acetic acid spreading is a novel technique for the diagnosis of superficial gastric cancers.