胃間葉系腫瘍の画像診断―特に狭義のGISTの特徴像について

Radiological Imaging of Gastric GIST

要旨　胃の間葉系腫瘍55病変(53症例)について，CD34，c-kit protein，S-100 protein，Desmin，α-smooth muscle actin(SMA)の5種類の免疫染色を行い，免疫組織化学ならびに臨床病理学的検討を行った．この中でCD34およびc-kit陽性を示す腫瘍をCajal cell type(狭義のGIST)とし，他の間葉系腫瘍と比較し検討した．免疫染色を施行して再分類を行った結果では，これまで平滑筋肉腫として診断されていた31例中17例がGISTに，2病変が神経鞘腫に診断が訂正された．しかし，平滑筋腫からGISTへと再分類された腫瘍はなかった．腫瘍の形状をみてみるとGISTは多結節性を示す傾向にあり，さらに小さな腫瘍でも潰瘍形成を呈する頻度が高かった．また，CT，MRIでは，GISTは18病変中13病変において内部に変性所見がみられ，そのうち9病変は散在性の分布を示した．

　Immunohistochemical and clinicopathological features of 55 gastrointestinal mesenchymal tumor of the stomach (53 cases) were studied by CD34, c-kit protein, Desmin, S-100 protein, and a-smooth muscle actin (SMA). Tumor originated from Cajal cell (GIST), which can be demonstrated by immunostaining for CD34 and c-kit, were selected in these cases and compared with other mesenchymal gastric tumors. Immunostaining studies urged to re-diagnose 17 out of 31 cases of previously diagnosed leiomyosarcoma to GIST and 2 out of 31 cases to Schwann cell type tumors. However, there was no re-diagnosis from leiomyoma to GIST. Although the tumor size was small, GIST was tended to be multi-nodular in shape, with high incidence of ulceration on the surface. CT and MRI scans showed degenerative parts within the tumor in 13 out of 18 GIST cases and scattered lesions in 9 cases of them.