早期食道癌深達度診断の進歩―FICE併用拡大内視鏡を中心に

Progression of Magnifying Endoscopy with FICE in Diagnosis of the Invasion Depth of Early Esophageal Carcinoma

要旨　拡大内視鏡を用いた微細血管像による，食道表在癌の深達度診断の成績と問題点について検討した．使用機種は主にFTS社製EG-590ZWを用い，血管強調モードのFICEを併用した．微細血管パターンのtype 3とtype 4は癌に特徴的な血管像で，ストレッチされたtype 4血管で囲まれたAVA/SSIVは，その大きさから4S，4M，4Lの3つのカテゴリーに亜分類される．type 3とtype 4Sをm1・m2癌，type 4Mをm3・sm1癌，type 4Lをsm2・sm3癌の診断規準とすると，m1・m2癌の診断率は99.6％，m3・sm1癌は68.8％，sm2・sm3癌は85.3％，全体の正診率は377病巣中351病巣（93.1％）であった．AVAを形成しないreticularな血管から成るtype 4Rは，低分化型や特殊な組織型の癌，INFcの浸潤様式を示す病変でみられた．深達度診断で前進した点は，m1・m2癌の診断レベルが向上したこと，細かな浸潤部を読影できるようになったこと，癌の進展形態や浸潤様式が鑑別できるようになったことである．誤診の原因は微小浸潤，角化の強い病変や表層が浅い癌で覆われながら，深部で細かい癌蜂巣がバラバラに浸潤していたことによる浅読みであった．病変の厚みと血管像の間に乖離がある場合には，高周波数細径超音波プローブを併用した深達度評価が必要である．

　We examined the results and problems involved in diagnosis of the invasion depth of superficial esophageal cancer on the basis of microvascular patterns on magnifying endoscopy. We mainly used the EG-590ZW（FTS Systems, Tokyo, Japan）and Fujinon intelligent color enhancement（FICE）to enhance vascular patterns. Microvascular patterns of type 3 and type 4 were characteristically seen in cancer. These vessels can be classified into 3 subcategories on the basis of the size of avascular areas（AVA）surrounded by stretched type 4 vessels or the size of surrounding areas with stretched irregular vessels（SSIV）: 4S, 4M, and 4L. When type 3 and type 4S vessels were considered the diagnostic criteria for m or m cancer, type 4M vessels for m or sm cancer, and type 4L vessels for sm or sm cancer, the rate of correct diagnosis was 99.6% for m or m cancer, 68.8% for m or sm cancer, and 85.3% for sm or sm cancer. The rate of correct diagnosis for all cancers was 93.1%（351 of 377 lesions）. Type 4R vessels consisting of reticular vessels without formation of AVAs were found in poorly differentiated carcinomas, specific histologic types of carcinoma, and lesions showing INFc infiltrative patterns. Progress in diagnosis of the depth of tumor invasion has improved the diagnosis of m or m cancers and permitted the visualization of small sites of invasion and the assessment of the development and invasion patterns of tumors. Misdiagnosis was caused by lesions with microinvasion or marked keratinization and by tumors that were covered with shallow superficial layers of cancer cells, but had sporadic invasion foci in deeper regions. The high-frequency miniature ultrasonic probe should also evaluate the depth of tumor invasion showing dissociation between lesion thickness and vascular patterns.