早期大腸癌の深達度診断におけるEUSと拡大内視鏡の位置づけ―拡大内視鏡を重要視する立場から

Diagnostic Ability of Staging in Early Colorectal Cancer: Comparison with Magnifying Colono-scopy and Endoscopic Ultrasonography

要旨　工藤らのpit pattern分類は，組織診断とよく対応することから拡大内視鏡診断に応用されてきた．しかし，現在までの成績と治療の適応を視野に入れて考えた場合，臨床的に無処置で良い非腫瘍性病変（Ⅰ・Ⅱ型pit），内視鏡切除可能な腺腫からsm₁癌（ⅢL・Ⅲs・Ⅳ型およびⅤA型の一部），外科的手術が優先されるsm₂以深癌の3群に分類可能である．今回，われわれはこの大別した分類を用いて拡大内視鏡とEUSとの正診率を比較した．同一病変にEUSと拡大内視鏡の両者を施行した早期癌123病変（隆起型75，表面型48病変）における深達度診断能の比較では，肉眼型にかかわらず拡大群89％（110/123）がEUS群79％（97/123）に比べ良好な成績であった（p＝0.0245）．EUSで診断困難とされる腫瘍高11mm以上の隆起型腫瘍においても拡大の正診率は，86％（57/66）と良好な成績であった．早期大腸癌に対する深達度診断能は，肉眼型にかかわらず拡大内視鏡がEUSを凌駕する成績であることから，現時点では通常＋拡大観察による内視鏡診断で十分と考えられる．

　There is good correspondence between Kudo's classification of the mucosal crypt pattern and histological findings, using magnifying colonoscopy (Type Ⅰ and Ⅱ are non-neoplastic lesions, type Ⅲ or Ⅳ are intramucosal neoplastic lesions, and type Ⅴ are deep invasive carcinomas, respectively). Kudo's classification was modified into three basic types ; non-neoplastic, non-invasive and invasive. The accuracy rates of invasiondepth diagnoses of early colorectal cancer by magnifying colonoscopy and endoscopic ultrasonography (EUS) were compared. There were 123 lesions (protruding lesions, 75, superficial lesions, 48), on which both EUS and magnifying colonoscopy were performed. The accuracy rate was higher for magnifying colonoscopy (89%; 110/ 123) than for EUS (79%; 97/ 123). Moreover, the performance of EUS is time consuming and a little troublesome. And protruding tumors or large colorectal cancers are difficult to evaluate with EUS due to its low degree of penetration. On the other hand, magnifying colonoscopy is more expeditious and costeffective, and detection and adequate examination of tumors tended to be more effective with magnifying colonoscopy than with EUS. In conclusion, magnifying colonoscopy is a better instrument than EUS for diagnosis of the depth of invasion of early colorectal cancer.