早期消化管癌の深達度診断─基本と進め方

Diagnosis of Invasion Depth for Early Carcinomas of Digestive Tract: Basis and Procedures

要旨●早期消化管癌に対する深達度診断を行う際には，食道，胃，大腸という癌発生の場による違いを考慮して読影する必要がある．読影・診断すべき所見は，基本的には，隆起，びらん，潰瘍，粘膜の色調である．これらの基本形をもとに大きさと肉眼型を決定し深達度診断を行う．深達度診断の基本として，病変周囲の正常粘膜から読影を開始し，病変境界部の性状を読影した後に，病変の中央部に向かって順に読影を進めることが重要である．病変の中央部分からいきなり読影を開始することは，深達度診断を誤る原因のひとつとなる．（NBI）拡大内視鏡観察は通常観察による深達度の確定診断を目的として，または通常観察で疑問が生じた病変内の限局した部位の精査として行うべきである．同様に超音波内視鏡検査（endoscopic ultrasonography ; EUS）も通常観察や拡大観察を行ってもなお，確定診断が得られない場合に追加することが効率のよい深達度診断法と考える．

　For diagnosing the invasion depth for early carcinomas of the digestive tract, it is necessary to review different findings associated with each carcinoma : esophageal, gastric, and colorectal. Lesion findings that require basic and essential examining and analyses are protrusion, erosion, ulcer, and mucosal color. Based on these four parameters, lesion size and macroscopic type can be accurately determined, and the invasion depth can be diagnosed. As a fundamental method of diagnosing the invasion depth, the abnormal findings should be interpreted from the outside region of the lesion, followed by the border of the lesion, and finally, the inside of the lesion. The interpretation of the abnormal findings started from the inside of the lesion may be one of the reasons leading to the misdiagnosis of the invasion depth. Further, for the detailed examination of suspected localized part of the lesion, it is better to proceed with magnifying endoscopy（with narrow band images）for the confirmed diagnosis of the depth than conventional endoscopy using dye-spraying method. Similarly, endoscopic ultrasonography may be conducted when the invasion depth is not accurately determined after conventional endoscopy and magnifying endoscopy.