1) 食道

Diagnosis and Treatment of Leiomyoma, Neurogenic Tumor and Gastrointestinal Stromal Tumor (GIST) in the Esophagus

要旨　食道では平滑筋腫が間葉系腫瘍（GIMT）のほとんどを占め，GISTと平滑筋肉腫，神経鞘腫の頻度は低い．GISTと食道平滑筋肉腫は下部食道に多く，5cmを超えるものが80％を占め，10cm以上のものも高頻度にみられる．5cm以下の症例に再発は少ない．原病死例は10cmを超えるものに多く，血行性転移が多い．自験例27例の検討では，平滑筋腫25例，平滑筋肉腫1例，GIST1例であった．良悪性の判定は腫瘍径，急速増大，細胞密度と核分裂数が重要で，予後判定因子としてc-kit遺伝子変異，Ki-67，テロメラーゼ活性などが指摘されている．EUSはGIMTの診断に必要不可欠で，EUS-FNABの併用でGIMT以外のSMTおよびGIMTの鑑別を行うことができる．組織学的評価が治療方針を決定するうえで重要な意味を持つ．しかし，悪性度の評価で最も重要視されている核分裂数はEUS-FNABで得られる組織では判定が難しいため，GISTと診断された場合は積極的に切除を行い，有症状や急速増大および5cmを超える平滑筋腫は腫瘍切除を行う必要があると考えられる．生検材料レベルで良悪性診断が判定できるマーカーの検討が望まれる．

　Most of gastrointestinal mesenchymal tumors (GIMT) in the esophagus are leiomyoma, but the incidence of gastrointestinal stromal tumor (GIST), leiomyosarcoma and schwannoma is low. In cases of GIST and leiomyosarcoma, often seen in the lower esophagus, the diameter of the tumor exceeded5cm in80％ and even tumors of10cm or larger were not rare. Recurrence rate was low after treatment of tumors not more than5cm in diameter. Fatal cases of this disease were encountered mostly when the tumor was larger than10cm, and the causes in many of them were distant metastasis. Of a total of27cases of GIMT, there were25cases of leiomyoma, 1case of leiomyosarcoma and1case of GIST. In the assessment of malignancy, it is important to examine tumor size, acceleration in tumor growth, cell density and mitotic count. Mutations in the c-kit gene, Ki-67labeling index, and telomerase activity have been reported to have prognostic implications. EUS is essential for establishing the diagnosis of GIMT and differentiation between GIMT and other submucosal tumors is enabled by EUS-guided fine needle aspiration biopsy (EUS-FNAB). To decide on a treatment policy, histological evaluations are important. However, examination of mitotic count, which is considered to be critical for evaluating tumor malignancy, is difficult when using only specimens obtained by EUS-FNAB. Thus surgical resection of the tumor should be carried out when a tumor is diagnosed as GIST. Surgery is considered to be necessary also in cases of leiomyoma with subjective symptoms, rapid tumor growth, and with dimensions larger than5cm. Further investigation is expected to develop a method of diagnosing tumor marker, using biopsy specimens.

　1) Department of Gastroenterology, Saitama Cancer Center, Saitama, Japan