小腸悪性腫瘍の病理学的特徴―小腸GISTの病理学的特徴

Clinicopathological Characteristics of GISTs（Gastrointestinal Stromal Tumors）in the Small Intestine

要旨　消化管において最も発生頻度の高い間葉系腫瘍は消化管間質腫瘍（gastrointestinal stromal tumor ; GIST）で，これは小腸に限定しても同様であるが，炎症性線維性ポリープ，炎症性筋線維芽細胞腫，腹膜，腸間膜に発生する孤立性線維性腫瘍，平滑筋肉腫，デスモイド腫瘍などの浸潤と正確に鑑別することが重要である．胃に発生するGISTと同様，正確な病理診断は術後のフォロー，治療に必須であり，診断名だけでなく正確な悪性度の評価が必要である．現在，複数の悪性度分類が存在するが，どの分類を用いて診断しているのか臨床医と確認しておくことが重要である．また，小腸にはまれに症候性の多発性GISTが発生するが，腹膜播種，転移と誤診してはならない．小腸GISTの診断には適切な免疫染色，悪性度の評価だけでなく，患者の背景を考慮した亜型診断が求められる．

　GISTs（gastrointestinal stromal tumors）are the most common mesenchymal tumors in the small intestine. The differential diagnosis of small intestinal GISTs includes other mesenchymal tumors, such as inflammatory fibroid polyps, inflammatory myofibroblastic tumors, solitary fibrous tumors, leiomyosarcomas, and desmoid tumors. In order to provide appropriate follow-up medical care for patients, it is necessary not only to diagnose each GIST, but also to grade the malignancy of each GIST. Because there are several systems used to grade GIST malignancy, pathologists must tell physicians which system was used for grading. GISTs occurring hereditary diseases often develop in multiple places of the small intestine, so careful analysis is necessary to differentiate GISTs of that type from disseminated sporadic GISTs. In addition to appropriate immunohistochemical techniques and malignancy potential grading, we must consider the subclassification of GISTs to arrive at a correct diagnosis of small intestinal GISTs.