粘膜下腫瘍

Gastric Submucosal Tumors

要旨●胃に生じる多彩な腫瘍性病変・非腫瘍性病変が“粘膜下腫瘍”の形態を呈するが，最も典型的な粘膜下腫瘍は間葉系腫瘍によるものであり，その多くがGIST（gastrointestinal stromal tumor）である．固有筋層に関連して発生し，粘膜下層側あるいは漿膜下から壁外に突出した腫瘤を形成する．腫瘍内の出血や囊胞化をしばしば伴う．切除されたGISTの再発・転移予測は最大径と核分裂像数に基づくリスク分類によって評価されているが，最近では，腫瘍の原発部位と腫瘍破裂を考慮したmodified Fletcher分類が広く使用されている．他の間葉系腫瘍や腫瘍様病変との鑑別，GISTであることの確実な病理診断が重要である．

　Various neoplastic and nonneoplastic lesions of the stomach morphologically resemble“submucosal tumors”, of which mesenchymal neoplasms are the most typical example. Mesenchymal neoplasms arising from the stomach are primarily GISTs（gastrointestinal stromal tumors）, which originate from the proper muscle layer and grow into the submucosa and/or subserosa, the latter forming an extragastric mass. They are often accompanied with intratumoral hemorrhage and/or cavity formation. Risk of recurrence and/or metastasis from GISTs is stratified by assessing the largest diameter and the mitotic count of the resected tumors. Recently, the modified Fletcher's risk stratification system, which considers both the primary tumor site and tumor rupture, is most widely used. for the risk assessment of GISTs. The reliable pathological diagnosis of GISTs and differentiating it from other mesenchymal tumors/tumor-like lesions are essential.