Barrett食道腺癌の病理学的特徴—SSBE由来Barrett食道腺癌の特徴

Characteristics of Pathological Findings in Short-segment Barrett's Esophagus-Derived Esophageal Adenocarcinoma

要旨●本邦に多くみられるSSBEは，病理組織学的に胃噴門腺粘膜（cardiac mucosa）が多い．cardiac mucosaの上皮成分は，粘膜表層を覆うMUC5AC陽性の腺窩上皮と，深部に存在するMUC6陽性の噴門腺により構成されている．噴門腺が存在する領域は，胎生期では非常に狭く，後天的に拡がると考えられ，Helicobacter pylori陽性患者では肛門側に，GERD患者では口側に拡がる．SSBEに発生したBarrett食道腺癌の早期病変内には，cardiac mucosaと同様の細胞分布（MUC5AC陽性細胞が管腔側，MUC6陽性細胞が深部）を呈する異型腺管が確認できることが多いため，SSBE由来Barrett食道腺癌はcardiac mucosaから発生したことが示唆される．SSBE由来Barrett食道腺癌は下部食道の右側の前壁（0〜3時方向）に認められることが多く，肉眼型では隆起型が多いと報告されている．また，SSBEはLSBEと同様に悪性腫瘍の発生母地となりうるが，LSBEよりは発癌リスクは低く，同時多発癌や異時多発癌が発生する可能性も非常に低い．

　Most of the SSBE（short-segment Barrett's esophagus）, which is often found among Japanese patients, is primarily composed of cardiac-type mucosa. The cardiac mucosa surface consists of MUC5AC-positive gastric foveolar epithelium, and the more profound part consists of MUC6-positive cardiac glands. The area where cardiac glands are present is extremely narrow during the embryonic period and is believed to spread. The cardiac mucosa spreads to the anal side in patients with Helicobacter pylori infection, and it also spreads to the oral side in patients with gastroesophageal reflux disease. Atypical glands exhibiting the same cell distribution as that of cardiac glands（MUC5AC-positive cells on the luminal side and MUC6-positive cells deep）can be detected in the part of Barrett's EAC（esophageal adenocarcinoma）derived from SSBE. This finding suggests that SSBE-derived Barrett's EAC is originated from cardiac mucosa. The lesion is often located at the right anterior wall（0-3 o'clock position）in the lower esophagus. It has been reported that the main macroscopic type is elevated. Although SSBE has the potential to develop EAC like LSBE, it has a lower risk for carcinogenesis than LSBE. SSBE is highly unlikely to develop simultaneous multiple cancers or extraordinary multiple cancers.