超音波内視鏡による早期胃癌の鑑別―内視鏡治療を目的に

Evaluation of the Degree of Gastric Cancer Invasion by Endoscopic Ultrasonography (EUS) for Endoscopic Treatment of Early Disease

要旨　早期胃癌の内視鏡治療を目的に，その適応条件の1要素である深達度診断について超音波内視鏡の診断能を検討した．術前にEUSを施行し切除標本との対比が可能であった胃癌500例について高エコー層の変化を基準に，m癌，sm癌，pm癌，ss以深の癌に分類すると正診率は78.6％であった．内視鏡治療の対象となるm癌174例の正診率は77.0％で，内視鏡形態別には潰瘍性変化を伴うⅡc癌，Borrmann 1型胃癌で低い正診率を示した．部位，組織型，間質，増殖形態別の正診率に大きな差を認めなかった．Ⅱc型sm癌をその浸潤の程度からsm 1，2，3に分類し，内視鏡治療の適応となりうるm＋sm癌の正診率を検討すると86.5％となった．m癌のリンパ節転移率は今回の検討症例では2例（1.1％）で，潰瘍性変化を伴う低分化腺癌例であったが，EUSによる指摘はできなかった．EUSによる内視鏡治療の術前深達度診断は治療の適応を確認すると共に，内視鏡形態，組織型と合わせリンパ節転移の頻度を推定する手段として評価できるものであった．

　Endoscopic ultrasonography (EUS) was evaluated for assessment of depth of gastric cancer invasion required in the endoscopic treatment of early gastric cancer. Five hundreds cases of histologically confirmed gastric cancer were examined by EUS. The depth of cancer invasion was classified as mucosal, submucosal, lamina propria, sub-serosal. Overall accuracy was 78.6% for all types. Accuracy of 174 cases of mucosal cancer was 77.0%. The accuracy rates were lower in type Ⅱc early cancer and Borrmann type 1 advanced cancer but there were no significant differences of the accuracy rate in the location of tumor, histological type, the pattern of invasivity. In order to evaluate the EUS assessment of depth of cancer invasion more precisely, extent of invasion into the submucosa was divided into 3 subtypes (sm₁, sm₂, and sm₃). Accuracy rate of detecting mucosal cancer and sm₁ cancer was 86.5%. However, the sensitivity of metastatic disease to lymph nodes was poor.

　We concluded that EUS was useful for evaluating the depth of neoplastic invasion in the preoperative application of endoscopic treatment to early gastric cancer.