特異な形態を示した胃噴門部平滑筋肉腫（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79歳，男性．心窩部痛にて当科受診．上部消化管内視鏡検査にて胃噴門部に隆起性病変を認められたため，精査加療目的で入院となった．胃X線検査では径約4cmの隆起性病変を認めた．胃内視鏡では隆起の立ち上がりは周囲粘膜と同様の粘膜で覆われているが，表面は大部分粘膜が脱落し，腫瘍が露出していた．露出面は暗赤色調を呈し易出血性であった．胃噴門部の悪性粘膜下腫瘍の診断にて胃全摘および脾摘，リンパ節郭清術施行．切除標本では大きさ3×3×2.5cmの砲台状の粘膜下腫瘍で広く浅い潰瘍を形成するという特異な形態を示した．組織診断はH・E染色では円形，長楕円形，紡錘形の細胞が錯綜し，部分的に胞巣状になり，密に増殖する間葉系腫瘍であり，核分裂を×20で1視野に5個以上と多数認めた．H・E染色からは平滑筋肉腫とされた．免疫組織化学的染色では平滑筋アクチン，デスミン，ビメンチン，S-100，NSE陰性，CD34，c-kit陽性となり，消化管間葉系腫瘍をGISTと総称する分類ではGIST，uncommitted type，malignancyとなった．GIST分類はその必要性を認めないとする立場の意見があり，いまだに広く使用されていないのが現状と思われる．新しい消化管間葉系腫瘍の分類として更に症例の検討が行われ臨床的有用性が高められることが望まれる．

　A 79-year-old man was admitted to our hospital for a close examination and treatment of a tumor in the cardiac region of the stomach. X-ray and endoscopic examinations showed the protruding tumor with a wide and shallow ulcer. The mucosa overlying the tumor was denuded and the dark and smooth surface of the tumor was observed. EUS revealed it iso echoic tumor which involved the whole layer of the muscularis propria. The entire view of the tumor was unusual. In the resected specimen, the tumor was 3 cm in diameter, and it looked battery-like in configuration. At first, histological diagnosis by H･E staining was leiomyosarcoma. In imunohistochemical staining, smooth muscle actine, desmin, neuron specific enolase, S-100, and KP-1 were stained negative, and CD34 and c-kit were positive. As a result of immunohistolchemical study, this tumor was finally diagnosed as being in the group of gastrointestinal stromal tumors (GIST) of uncommitted type and malignancy. Though this new concept was not accepted by many, we hoped to have more cases to study and to evaluate its clinical importance.