食道表在癌深達度診断の進歩―拡大内視鏡vsEUS：EUSの意義

Clinical Significance of Endoscopic Ultrasonography Versus Magnifying Endoscopy for Estimating the Depth of Tumor Invasion in Superficial Esophageal Cancer

要旨　食道表在癌の深達度診断における，拡大内視鏡とEUSの有用性と問題点を明らかにするとともに，EUSの役割について検討した．拡大内視鏡による微細血管パターンの観察で，通常観察では診断できなかった細かい深達度の読み分け，各部分の組織像の成り立ちを予測できる．深部浸潤部では多重状（multi-layered；ML），不整樹枝状（irregularly branched：IB），網状（reticular；R）のtype4血管が出現する．type4血管で囲まれたavascular area（AVA）の大きさから深達度診断が可能である．拡大観察の誤診例の多くは，表層がm₁・m₂癌などの浅い癌で覆われながら，その深部で微小浸潤していたり，結節状の癌蜂巣が浸潤したりする病巣であった．微小浸潤は拡大観察，EUSとも診断の限界であるが，隆起や肥厚が目立つ病変の評価にはEUS，特に高周波数細径超音波プローブが役立つ．また，AVAを形成しないtype4Rから成る病変（non-AVA）は低分化型癌やinfγの浸潤形態を呈することが多く，具体的な深達度診断にはEUSが必須である．

　We examined the usefulness and limitations of magnifying endoscopy and endoscopic ultrasonography (EUS) for estimating the depth of tumor invasion in superficial esophageal cancer. We also studied the role of EUS. Assessment of microvascular patterns on magnifying endoscopy was useful for evaluating the depth of tumors that could not be assessed by using conventional endoscopy, as well as for predicting histopathological features. Regions with deep tumor invasion were associated with multi-layered, irregularly branched, and reticular type 4 vessels. The sizes of avascular areas (AVAs) surrounded by type 4 vessels could be used to predict the depth of tumor invasion. Most cases misdiagnosed on magnifying endoscopy were lesions covered by superficial m₁ or m₂ cancers, overlying deeper areas of microinvasion or invasive nodular foci. Both magnifying endoscopy and EUS were of limited value for the diagnosis of microinvasion. However, EUS, particularly with the high-frequency miniature US probe, was useful for the evaluation of protruding or thickened lesions. type 4R lesions without the formation of AVA (non-AVA lesions) often showed invasion patterns typical of poorly differentiated carcinomas or lesions showing infiltrative growth and no distinct border with the surrounding tissue (infγ). EUS is essential for the evaluation of the depth of invasion of such lesions.