食道表在癌の深達度診断─拡大観察の有用性と留意点

Accuracy of the Japan Esophageal Society Classification of NBI-Magnifying Endoscopy in Diagnosing Superficial Esophageal Squamous CellCarcinoma Invasion Depth

要旨●食道表在癌の深達度診断に際し，さまざまなmodalityを駆使して行うことが重要である．井上・有馬分類を基盤に作成された日本食道学会拡大内視鏡分類による食道表在癌に対する深達度診断は正診率が高く，非常に有用な診断学である．特にB1血管は97.4％，B3血管は91.7％とともに正診率は90％を超え，特異度が高い．しかしB2血管の正診率は70％台であり，従来の通常観察に比べると高い傾向にあるものの，今後はB2血管の正診率をいかにして向上させるかが課題と思われる．さらに，B3血管の感度は40％台と低く，pSM2癌におけるB2血管の出現率が高いことを踏まえ，B2血管とpSM2癌との関連性を見い出すことが大切であると考える．また，病変内の血管形態の変化が最も高度な関心領域のほとんどが，病変全体の最深部を反映していたことより，拡大内視鏡による深達度診断は切除後の正確な病理診断，すなわち追加治療の適切な評価を行うために意義のある診断学と考える．

　The diagnostic accuracy of invasion depth in superficial esophageal squamous cell carcinoma（SCC）was prospectively evaluated at our institute according to a new classification system established by the Japan Esophageal Society（JES）. In this study, 306 consecutive lesions in 260 patients with superficial esophageal SCC and treated by endoscopic submucosal dissection（ESD）were enrolled from March 2011 to June 2014. Histologically, 241 lesions were diagnosed as pT1a-EP/LPM, 39 lesions as tumor depth of pT1a-MM or pT1b-SM1, and the remaining 26 lesions as pT1b-SM2. The accuracy rate of the tumor invasion depth of the targeted lesion diagnosed as type B1 vessels by magnifying endoscopy with narrow band imaging（NBI）was 97.4%（236/241）. The accuracy rate of type B2 and B3 vessels was 73.1%（38/53）and 91.7%（11/12）, respectively. The sensitivity was lowest for type B3 vessels with 47.8%. The problem associated with these results was the high incidence of type B2 vessel in pSM2 carcinomas. Although greater test accuracy is currently required regarding type B2 vessels, it is important to investigate the association between type B2 vessels and pSM2 carcinomas which may be of value in the future. On the other hand, as many targeted lesions involve deep tissues, diagnosis of tumor invasion depth using magnifying endoscopy may allow more accurate pathological assessment and appropriate evaluation of additional treatment needs.