特異な形態を呈した小腸GISTの1例

Gastrointestinal Stromal Tumor of the Small Intestine Presenting in a Peculiar Form, Report of a Case

要旨●患者は40歳代，男性．黒色便を主訴に来院し，貧血を認めたため入院となった．腹部造影CTにて近位空腸に造影効果の強い石灰化を伴う径約4cmの境界明瞭で内部不均一な類円形腫瘤を認めた．小腸X線造影検査を行ったところ，表面平滑で圧迫による形態変化の乏しい腫瘤性病変として認識された．小腸内視鏡検査では正常粘膜に覆われた立ち上がりのなだらかな腫瘍で，中心に陥凹を有し，一部びらんを疑う所見を認めたが潰瘍は認められなかった．生検の結果，小腸GIST（gastrointestinal stromal tumor）と診断され，腹腔鏡下小腸部分切除術を施行した．中心陥凹を形成した機序として，腫瘍の筋層から粘膜下層方向への浸潤の程度が場所により不均等で，粘膜下層浸潤のない中心部分が相対的に陥凹を形成した可能性や，腫瘍内囊胞の自潰により中心陥凹が形成された可能性が推測された．

　A man in his 40s was admitted to our hospital with anemia and melena. Contrast-enhanced computed tomography showed a heterogeneous enhanced structure with calcification in the jejunum. Small bowel series and transoral single-balloon enteroscopy led to the detection of a protruding tumor characterized with an oval, smooth surface covered with normal epithelium and central depression without erosion and ulceration. The lesion was diagnosed as a GIST（gastrointestinal stromal tumor）by pathological examination after laparoscopic resection was performed. Unlike our case, small bowel GIST complicated bleeding is usually accompanied by mucosal injury. The depressed region may be formed due to an imbalance of proliferation that occurred between the marginal and central areas of the tumor. Therefore, the center of the lesion may be relatively depressed.