早期胃癌診断の現況と将来―内視鏡の立場から―拡大内視鏡と切開・剥離法は早期胃癌診断をどう変えたか？

Current Problems and the Future Prospects for Endoscopic Diagnosis of Early Gastric Cancer―How Have Magnified Endoscopy and Endoscopic Submucosal Dissection Techniques Changed the Status of Endoscopic Diagnosis of Early Gastric Cancer?

要旨　目的：当科における早期胃癌の内視鏡診断の最新の現況を求めた．対象と方法：拡大内視鏡診断と内視鏡的切開・剥離法が導入され技術的に最も安定した最近の1年間に診断治療された早期胃癌97病変を対象として以下の項目について検討した．①通常内視鏡で悪性と診断できない非典型的な癌の頻度と特徴，②内視鏡による深達度診断能，③ESD術前の内視鏡による境界診断能．成績：①非典型例の頻度は15％であった．非典型例の特徴は，微小癌，IIb，凹凸や色調変化が少ないIIaや境界部で蚕食像を読影できないIIcであった．これらの組織型はすべて分化型癌であり，拡大内視鏡により悪性と診断可能であった．②については，正診率は95％と高く，実際の臨床の治療法の選択は適切に行われていた．③については，通常内視鏡で境界が診断困難な病変は13例（18％）であった．境界診断困難病変すべてに対し，拡大内視鏡診断が施行されており，11例（15％）で全周にわたり境界診断が可能であった．しかし拡大内視鏡を用いても残りの2例（3％），すなわち広いIIa集簇型に随伴したIIb面の全周にたる境界診断には限界があった．結論：切開・剥離法の導入と内視鏡的粘膜切除術の適応拡大により多彩な病変を診断する必要が生じていた．従来通常内視鏡で診断が不可能であった単独IIbや微小癌，随伴IIbの診断に，微小血管構築像に基づく新しい拡大内視鏡診断法は大きく寄与していた．

　Aim : The aim of the study was to clarify current problems in preoperative diagnosis of early gastric cancer.

　Methods : We investigated the following subjects by reviewing the endoscopic findings, the endoscopic reports and the histopathological findings of 97 consecutive early gastric cancers which have been diagnosed and resected during the last 12 months. (1) The incidence and characteristics of early gastric cancer which did not reveal typical endoscopic morphology characteristic of carcinoma, (2) the accuracy of diagnosis of the depth of invasion of carcinomas, and (3) the incidence and the morphology of lesions whose margins could not be determined by endoscopic findings alone.

　Results : (1) The incidence of atypical lesions was 15 ％. The characteristic morphologies of these lesions were minute cancers, early gastric cancers of the superficial flat-type, early gastric cancers of the superficial-elevated type that showed little change in color and surface structure and early gastric cancers of the superficial-depressed type that revealed no irregularity at the margin. However, these cases could be correctly diagnosed by magnified endoscopy based on microvascular architecture. (2) The diagnostic accuracy of the depth of invasion of the carcinoma was 95 ％, which was accurate enough to accept for clinical practice. (3) The incidence of lesions whose entire margins could not be determined by ordinary endoscopy was 18 ％. Nevertheless, magnifying endoscopy was successful in determining the entire margin in 15 ％ out of the 18 ％ of lesions with unclear margins.

　Conclusions : Magnified endoscopic examination was able to contribute significantly to the accurate diagnosis of early gastric cancer even in the cases of lesions which, by ordinary endoscopy alone, showed atypical findings for carcinoma.