sm胃癌に対する超音波内視鏡による診断能の検討

The Accuracy of Endoscopic Ultrasonography for Diagnosing Submucosal Invasive Gastric Cancer

要旨　通常型超音波内視鏡群1，109例，20MHz通常型超音波内視鏡群105例，超音波プローブ群302例の切除胃癌のうち，sm癌241例，19例，78例を対象として超音波内視鏡の深達度診断の現状の検討と将来展望，特に三次元超音波内視鏡につき報告した．sm癌の進行度は，従来のsm層の3等分による浅層(従来のsm₁)が絶対値では約1mmであることから，sm浸潤が1mm以下のものをsm₁，1～2mm以下のものをsm₂，2mmを超えるものをsm₃とし，更に，sm₁を0.5mm以下のsm_1aと0.5～1mm以下のsm_1bとして細分類した．超音波内視鏡による深達度診断成績は，sm_1a32.1％(18/56)，sm_1b57.1％(44/77)，sm₂76.9％(80/104)，sm₃87.1％(88/101)とやはりsm₁の成績は不良であった．この傾向は，sm浸潤の横への拡がり別の検討でも同様で，5mm以下の成績は49.4％と不良であった。組織型による深達度診断成績の差は明らかではなかったが，肉眼型による差は明らかで陥凹型，隆起型の成績が65.7％，61.0％と不良であった．微少浸潤の同定に三次元超音波内視鏡が期待されている．

　The recent status and future prospects of endoscopic ultrasonography for diagnosing the stages of gastric cancer was discussed in this paper using as subjects 1,109 lesions of gastric cancer in a conventional EUS group, 105 in 20 MHz conventional EUS group and 302 in an ultrasonic probe (USP) group. We classified submucosal invasion into four subgroups as follows; sm_1a means submucosal cancer invasion limited to less than 500 μm, sm_1b up to 1,000 μm, sm₂ up to 2,000 μm, and sm₃ over 2,000 μm. We made this classification because shallow submucosal invasion (sm₁) according to the former three group classification is about 1,000μm. Diagnostic accuracy of EUS is 32.1% in sm_1a, 57.1% in sm_1b 76.9% in sm₂, and 87.1% in sm₃. The tendency for these to be poor diagnostic accuracy for lesions with small invasion depth is also found in diagnosis of the width of their invasion. Whether it be well or poorly differentiated adenocarcinoma, there is no difference in the accuracy of EUS for diagnosis the stages of these gastric cancers. The EUS is able to confirm the differences in macroscopic type with good accuracy except in cases of depressed or protruded gastric cancers. We expected that problems involved in threedimensional endoscopic ultrasonography will be able to be resolved in the not too distant future.