胃粘膜下腫瘍の診断―超音波内視鏡による診断の進歩

Advancement in the Diagnosis of the Gastric Submucosal Tumor Brought About by Endoscopic Ultrasonography (EUS)

要旨　胃粘膜下腫瘍の診断において，従来からの画像診断を越えるEUSの長所は胃壁内の腫瘍像を明瞭に描出できることにある．胃粘膜下腫瘍の診断におけるEUSの有用性を明らかにするために，EUSで診断された40症例の胃粘膜下腫瘍と13症例の胃外圧迫における，X線および内視鏡検査の診断能を検討した．その結果，X線および内視鏡検査の正診率は胃粘膜下腫瘍の診断において88％（35/40例），胃外圧迫の診断において23％（3/13例）であった．次に，組織診断のついた胃粘膜下腫瘍18症例において，EUS所見から粘膜下腫瘍の組織診断が推定できるかどうかを検討した．その結果，EUS画像上における，腫瘍の内部エコーレベル，腫瘍と胃壁層構造との連続性，腫瘍の主病変の局在，腫瘍周囲の層構造の破壊性変化は腫瘍の組織の推定および良・悪性腫瘍の鑑別において大変重要な所見であった．更に，われわれはEUS画像を観察しながら3症例の胃粘膜下腫瘍の生検を試み，1例において成功した．

　The advantage of EUS over conventional imaging procedures in the diagnosis of gastric submucosal tumor (gastric SMT) is that it is able to clearly visualize the image of the tumor in the gastric wall. To clarify the usefulness of EUS in the diagnosis of gastric SMT, the diagnostic abilities of x-ray and endoscopic examination were investigated in 40 cases of gastric SMT and 13 cases of extra-gastric compression which had been diagnosed by EUS. As a result, the accuracy rate of x-ray and endoscopic examination was 88％ (35/40 cases) in the diagnosis of gastric SMT, and 23％ (3/13 cases) in that of extra-gastric compression.

　Next, in 18 cases of gastric SMT confirmed histologically, it was studied whether histological diagnosis of the SMT could be presumed through EUS findings. The result was that the internal echo-level of the SMT, the continuity between the SMT and the layered structure of the gastric wall, the location of the main lesion of the SMT and the destructive change of the layered structure surrounding the SMT on EUS images were very important indications in the presumption of the histology of the SMT, and in the differential diagnosis between malignant and benign SMT. Furthermore, we tried biopsy of the gastric SMT in 3 cases while observing the EUS images and succeeded in one case.