食道粘膜癌の初期浸潤像の診断―通常内視鏡の立場から

Diagnosis of Early Invasion Images of Esophageal Mucosal Cancer from the Viewpoint of Normal Endoscopy

要旨　食道T1a-LPM癌36病巣を対象として，初期浸潤の内視鏡像を検討した．LPM浸潤の程度を基底層周辺のわずかな浸潤（micro-invasion），LPM中層まで浸潤するもの（downward growth），LPM深部まで浸潤するもの（deep invasion）として評価した．micro-invasionは通常内視鏡ではとらえられず，拡大観察でも浸潤部を同定できないことが多かったが，35％の病変で500μm以下のAVA（AVA-small）の集簇が観察された．downward growthは拡大観察でAVA-smallを形成する頻度が増加したが，通常観察で白色微細顆粒や褪色調肥厚として認識できたのは20％にとどまった．deep invasionは通常観察で褪色調の顆粒状隆起，肥厚面や粗糙な領域として認識できた．拡大観察ではnon-looped irregular vessels〔食道学会分類Type B2〕で構成される3mm以下のAVA（AVA-middle）やType B2血管が観察された．腫瘍塊が大きくなって浸潤が進むとType B2血管で囲まれたAVAの大きさが増すが，micro-invasionのレベルでもdroplet infiltrationを示す病変では，Type B2血管で形成される微細なAVAを形成することが明らかとなった．

　We examined endoscopic images from early invasion of 36lesions of T1a-LPM esophagus cancer. The degree of LPM invasion was evaluated as micro-invasion（slight invasion of the basal layer area）, downward growth（invasion to the middle layer of LPM, and deep invasion（invasion to deeper parts of the LPM）. Micro-invasion cannot be detected by normal endoscopy. Even with magnified observation, the invaded part often cannot be identified, but aggregation of avascular area-small（AVA-small）under 500μm was observed in 35％ of lesions. With downward growth, AVA-small formation was observed more frequently on magnified observation, but fine white granules and discolored hyperplasia were recognized in only 20％ of normal observations. In deep invasion, discolored granular eminence, hyperplasia surface, and coarse grained areas were recognized in all normal observations. In magnified observations, avascular area-middle（AVA-middle）less than 3mm consisting of non-looped irregular vessels（Japanese Classification of Esophageal Cancer Type B2）and Type B2 blood vessels were observed. When invasion progressed as the size of the tumor mass increased, the size of AVA surrounded by Type B2 blood vessels increased. However, we found that in lesions showing droplet infiltration, fine AVA consisting of Type B2 blood vessels was formed even at the micro-invasion level.