表在型Barrett食道癌の超音波内視鏡診断

Endoscopic Ultrasonography in the Diagnosis of Superficial Barrett's Esophageal Cancer

要旨　Barrett粘膜由来の表在型腺癌，12例13病巣を対象として，Barrett食道癌の深達度，伸展度診断におけるEUSの診断能について検討した．リニア型EUSは消化管壁の長軸方向に沿った断層像が描出されるため，層構造の変化からEGJを認識できるとともに，EUS上のhiatusとの位置関係を把握できる．腺上皮レベルにとどまるm癌の描出には限界があるが，それ以深の病変については，元々のEGJに接していなければ，食道側に主座を持つかどうかの判定は可能であると考えられた．sm深部癌の深達度診断は良好であった．細径超音波プローブではBarrett食道は，腺上皮が第2層の薄い低エコー層として描出され，粘膜筋板からsm層は線維化の影響で層構造の分離が不明瞭となり，びまん性に比較的高エコーに肥厚して描出されることが多く，健常食道壁とは描出のされ方が異なっていた．Barrett食道癌は不均一な低エコーを示すことが多く，その下面のsm層も線維化や食道腺，脈管などが混在して不均一なため境界が不鮮明となり，深達度診断が難しかった．線維化が高度な場合には，壁構造の中に占める相対的な位置関係から深達度を診断する必要があると考えられた．

　We undertook this study to determine whether EUS is useful in the diagnosis of the depth of invasion and extent of Barrett's esophageal cancer in 12 patients (13 lesions) with superficial adenocarcinoma arising in Barrett's epithelium. Linear-type EUS can produce transverse images of the gastrointestinal wall acquired in long-axis views and thereby identify the location of the esophagogastric junction on the basis of changes in wall structure. It can thus assess the position of the junction with respect to the esophageal hiatus on the acquired images. EUS is of limited value for the assessment of mucosal cancers remaining within the glandular epithelium, but was able to accurately estimate the depth of invasion of submucosal tumors. Using a miniature ultrasound probe Barrett's esophagus was revealed as a thin, hypoechoic layer in the second layer of the glandular epithelium. The region from the muscularis mucosae to the submucosa was characterized by a poorly demarcated wall structure due to fibrosis with diffuse, relatively hyperechoic wall thickening. Barrett's adenocarcinoma typically shows a hypoechoic heterogeneous pattern. The underlying submucosa is usually heterogeneous due to fibrosis and the intermingling of esophageal glands and vessels, resulting in a poorly demarcated border. The depth of invasion is therefore difficult to evaluate. In patients who have esophageal cancer with severe fibrosis, the depth of invasion should be evaluated on the basis of the relative location of the tumor in the wall structure.

　1) Department of Gastroenterology, Saitama Cancer Center, Saitama, Japan