特異な形態を呈した空腸GISTの1例

Jejunal GIST with Atypical Presentation, Report of a Case

要旨●患者は50歳代，男性．1年前に鉄欠乏性貧血がみられ，上下部消化管内視鏡検査で多発大腸憩室を指摘されていたが，黒色便と高度の貧血で再度受診した．腹部CT検査で近位空腸に石灰化巣を伴う径約3cmの輪郭明瞭な腫瘤が認められ，造影CT検査のdynamic studyでは動脈相から濃染された．小腸X線造影検査ではTreitz靱帯から約30cmの近位空腸に内腔を占居する長径35mmの表面平滑な半球状隆起を認め，隆起の口側にはさらに径約10mmの半球状小隆起を伴っていた．小腸内視鏡検査では管腔内を占居する大きな粘膜下腫瘤があり，口側には粘膜が脱落した小隆起を伴っていた．生検では確定診断できず，腹腔鏡下空腸部分切除術が行われた．腫瘤は粘膜下主体に漿膜下層まで発育する紡錘形の腫瘍細胞より構成されており，免疫組織化学染色の結果，GIST（gastrointestinal stromal tumor）と診断した．本例は管内発育が主体の腫瘤であり，口側に粘膜が脱落した小隆起を伴っていた点でGISTとしては非典型的な形態を呈した病変であった．

　A 59-year-old man presented to our hospital with tarry stool and severe anemia. One year ago, he had undergone upper gastrointestinal endoscopy and colonoscopy to investigate the causes of iron-deficiency anemia, and the results disclosed colonic diverticula.

　When he presented this time, abdominal CT revealed a well-demarcated mass in the proximal jejunum measuring approximately 30mm ; a tiny calcification was also visualized in the mass. On contrast study, the lesion was remarkably enhanced in the arterial phase. Small-bowel barium X-ray also delineated a hemispherical mass of 35mm in diameter that almost occupied the jejunal lumen at a point 30cm distal to the ligament of Treitz. A small, hemispherical prominence was observed on the oral side of the lesion. Single-balloon enteroscopy was performed, and it revealed a large submucosal tumor occupying the lumen. A prominence without mucosa was observed on the lesion. Partial resection of the jejunum was performed laparoscopically. On histopathological examination, it was found that the tumor was composed of spindle-shaped tumor cells growing mainly in the submucosa and extended till the subserosa. A diagnosis of GIST（gastrointestinal stromal tumor）was confirmed from the results of immunohistochemical staining. This case was considered to be an atypical presentation of GIST because the tumor had mainly grown intraluminally and was accompanied by a prominence without mucosa on it.