食道表在癌の深達度診断を誤った要因―内視鏡の立場から

Difficulties in Endoscopic Estimation of Depth of Invasion in Cases of Superficial Esophageal Cancer

要旨　食道表在癌において，深達度診断は治療法を選択する上で最も重要な要素である．色素を併用した内視鏡検査および拡大内視鏡観察を行っても，食道表在癌の深達度診断では，15％に誤診を認めた．浅読み症例は39例65％，深読み症例は21例35％であった．浅読み症例の大半は0-IIcであったが，深読み症例には，0-I，0-IIa，0-IIIの各病型が含まれていた．浅く診断した要因としては，①微小浸潤，②導管や食道腺の浸潤で示されるような食道壁の正常構造を破壊しない浸潤，③腺扁平上皮癌のように表面から浸潤部分の組織型が予測できない場合，④癌巣の表面を再生上皮が覆い表面性状が読影できない場合が挙げられた．逆に，深く診断した要因としては，①乳頭状増殖を示す0-Iplや，②上方発育型を示す白色調の0-IIaは，病変の形態から判断し深く診断していた．③固有筋層への圧排型の発育例は浸潤との鑑別が困難なために深く診断していた．また，非常にまれな場合として，④粘膜下腫瘍に合併した食道癌は，病巣内に隆起を伴う癌として扱われる可能性が高く，粘膜下腫瘍の存在診断が困難なため，深達度を深く診断していた．

　In cases with superficial esophageal cancer, we can employ today several advanced diagnostic measures such as endoscopic staining, ultrasonography and magnifying observation for estimation of cancer invasion. 402 cases of superficial esophageal cancer were included in this study in order to gauge the accuracy and recognize the difficulties in endoscopic estimation of cancer invasion. Esophagectomy was carried out on 142 cases and endoscopic mucosal resection on 260 cases. The incidence of misdiagnosis was noted in 15％ of all cases (over estimation: 5.2％ and under estimation: 9.7％). Type 0-IIc lesion is the most frequent among under estimated cases and type 0-I and 0-III the most frequent among cases with over estimation. Pathological studies on resected specimens of cases with under estimation revealed that endoscopic estimation of depth of invasion is difficult in cases with narrow cancer invasion into the deeper layer, cancer cell infiltration preserving normal tissue structures, deeper invasion of cancer cells with different histological type from covering squamous cell carcinoma and cancer tissue covered by regenerated stratified squamous epithelium. Some superficial esophageal cancers of protruded type were frequently over estimated as submucosal cancer when they had only papillary growth or poor tendency to invade into the deeper layer. We also encountered a few case which were estimated as submucosal cancers, but were actually mucosal cancers situated on top of benign submucosal tumors.

　1) Department of Endoscopy, Tokyo Metropolitan Komagome Hospital, Tokyo