噴門部の胃平滑筋肉腫（GIST，uncommitted type）の1例

Leiomyosarcoma (GIST, Uncommitted Type) in the Cardiac Region of the Stomach, Report of a Case

要旨　患者は45歳，男性．健診の胃X線検査で異常陰影を指摘され本院に入院した．胃X線検査では噴門部中央に潰瘍のある大きな腫瘤陰影が認められた．内視鏡検査では粘膜下腫瘍と診断され，潰瘍部分からの生検で平滑筋肉腫と診断された．CTでは腫瘤は胃壁外に発育していた．切除標本では，胃壁外に発育した8×4.8×4.8cmの腫瘤で，粘膜面に潰瘍形成が認められた．H・E染色による病理組織診断では，細胞異型，核異型を持った紡錘形の細胞から成る組織像は細胞密度が高く，核分裂像も多くみられる（18/10HPF）ことより，胃平滑筋肉腫と診断された．免疫組織学的染色を行うとS100，デスミン，平滑筋アクチンは陰性で，ビメンチン，また，幼若な間葉系細胞に染まるCD34が陽性であった．免疫組織学的見地からこれらの腫瘍をgastrointestinal stromal tumor（GIST）に入れて考えるという観点から，この腫瘍はGISTのuncommitted typeに分類された．今後，このような免疫組織化学的検討が，臨床的には治療法の選択，予後の判定に役立つことが期待される．

　This is a case of a 45-year-old man in whom x-ray examination at an annual health check revealed abnormal findings in the stomach. The x-ray examination showed a large tumor shadow with central ulceration in the cardiac region. In the endoscopic examination, the mass was diagnosed as a submucosal tumor and the biopsy from the ulcer revealed the histological findings of leiomyosarcoma. The mass showed exogastric growth in the CT film. The operated specimen with a mass measuring 8.0×4.8×4.8 cm, had large ulceration at the mucosal surface. The histological diagnosis by H・E staining, was leiomyosarcoma because of the f findings of atypical spindle cells with a high density of cellurarity and a large number of mitosis (18/10 HPF). Immunohistochemical staining revealed S100, desmin, and smooth muscle actin were stained negative and bimentin and CD34 were stained positive. This tumor was classified in the group of gastrointestinal stromal tumors (GIST) of uncommitted type. New concepts are required conceiving the prognosis and clinical treatment for this kind of tumor.