早期胃癌の術前診断（EMR適応病変を中心に）―内視鏡の立場から

Preoperative (EMR) Diagnosis of Early Gastric Cancer from the View Point of Endoscopy

要旨　根治を目的にEMRを施行した149例，155病変を対象とし，EMRを施行する場合の術前診断の現状と問題点について検討した，隆起型78病変，平坦・陥凹型77病変とほぼ同数であった．X線により発見された病変は26病変(16.8％)，内視鏡で発見された病変は129病変(83.2％)であった．術前の範囲診断では，隆起型の誤診例はなく，平坦・陥凹型の2例に誤診例がみられた．深達度の正診率は，隆起型93.6％，平坦・陥凹型89.6％であった．深達度別の正診率は，m癌97.2％，sm癌37.5％(隆起型50％，平坦・陥凹型30％)であった．同時性多発胃癌は9例(6.0％)にみられ，9例中7例(77.8％)は2病変ともに隆起型の癌であった，異時性多発胃癌は8例(5.4％)にみられ，8例中5例(62.5％)は，2年以内に発見されていた．遺残・再発は4例(2.7％)にみられた，EMR前の範囲診断では，正診2例，誤診2例(境界が不明瞭な病変1例，胃角後壁に病変が存在し観察が不十分1例)であった．EMRが可能な病変の拾い上げ診断には，特に平坦・陥凹型の病変についてはX線検査のみでは限界があり内視鏡の併用が必要と考えられた．EMRを前提とした術前診断では，色素法を用いた詳細な観察が重要であり，境界が不明瞭な病変にはステップバイオプシーの併用も有用である．sm微小浸潤(sm₁)については内視鏡診断の限界と考えられた．

　We performed curative endoscopic mucosal resection (EMR) in 149 patients (155 lesions) with the purpose of studying the current status and problems of preoperative diagnosis for EMR. Similar numbers of protruded type lesions (78) and flat/depressed type lesions (77) were studied. Twenty-six lesions (16.8％) were detected on X-ray film, and 129 (83.2％) were detected by endoscopic examination. The extent of tumor invasion was preoperatively misdiagnosed in 2 patients with flat/depressed type lesions but in none of the patients with protruded type lesions. The depth of invasion was correctly estimated for 93.6％ of protruded type lesions as compared with 89.6％ of flat/depressed type lesions. When classified according to the depth of invasion, 97.2％ of mucosal carcinomas and 37.5％ of submucosal carcinomas (protruded type, 50％; flat/depressed type 30％) were accurately diagnosed before treatment. Synchronous gastric carcinomas were diagnosed in 9 patients (6.0％). Both lesions were protruded type in 7 (77.8％) of these patients. Metachronous gastric carcinomas were diagnosed in 8 patients (5.4％), The second tumor was detected within 2 years in 5 (62.5％) of these patients. Four patients (2.7％) had residual tumor or recurrence. The extent of tumor invasion was correctly diagnosed before EMR in 2 of these patients and incorrectly diagnosed in the other 2 (indistinct tumor border in one and the impossibility of adequate examination in the other, becouse of its being located in the posterior wall of the angulus. Our results indicate that radiographic examination alone has limitations in the detection and diagnosis of lesions able to be treated by EMR, particularly in patients with flat/depressed type lesions. Endoscopic examination should therefore be performed concurrently. The preoperative preparations for EMR should include detailed examinations after spraying lesions with dye. Concurrent step biopsy is also useful for the assessment of poorly demarcated lesions. Submucosal microinvasion (sm₁) is considered to represent the limit of endoscopic diagnosis.