GISTの臨床的取り扱い―胃・小腸を中心に

Clinical Aspects of Gastrointestinal Stromal Tumor (GIST)

要旨　これまで筋原性腫瘍が大部分を占めると考えられてきた消化管の紡錘形細胞腫瘍は，近年の免疫組織化学の知見に基づき，その多くがGISTという概念で包括的に論じられるようになった．われわれもこの考え方に従い，胃と小腸を中心にその臨床的取り扱いを検討した．市立豊中病院でこれまでに経験した症例は，胃30例，小腸26例(十二指腸7例，空腸13例，回腸6例)である．良悪の判定は，主に腫瘍組織の核分裂数を指標とし，良性・低悪性度，高悪性度の三段階に分類したが，これは予後とよく相関していた．GISTを臨床的に取り扱う上で最も重要なことは腫瘍の大きさと発育形式であり，可能な限り縮小手術(部分切除あるいは局所切除)にとどめるべきである．高悪性度と判定したものは全例肝または腹膜転移で死亡し，治療成績は極めて悪い．最近，c-kit陽性腫瘍に対してTyrosine kinase阻害剤を治療に応用し，効果が期待されている．低悪性度の腫瘍は術後10年以上を経て再発(肝転移)するものがあり，長期にわたる経過観察が必要である．なお，GISTは，臓器により悪性度が異なり，胃に比べて小腸では悪性度の高いものが多く，予後不良であった．

　The term “gastrointestinal stromal tumor (GIST)” was introduced as a histogenetically neutral term referring to the main group of mesenchymal tumors of the digestive tract, which could be verified neither as neurogenic nor as myogenic in origin. Recent studies indicate that the majority of mesenchymal tumors of the gestrointestinal tract form a biologically distinctive group.

　The most practicable diagnostic criteria for GIST is the immunohistochemically determined c-kit (CD117) expression.

　According to the above concepts, we analysed a total of 30 gastric and 26 small intestinal (including 7 duodenal) cases of GIST, which were encountered in Toyonaka Municipal Hospital.

　In our series, about 10% of gastric and 30% of small intestinal cases of GIST were estimated as having high-grade malignancy with no lymphnode metastasis. All cases of high-grade GIST died within a few months after operation due to hepatic or peritoneal metastases.

　A large majority of low-grade GIST showed a clinically good course and only one patient with low-grade duodenal GIST died due to hepatic metastasis and local recurrence, 11 years after the operation.

　At present, we have a few way to control hematogenous metastasis of malignant GIST, so minimal operations (local or partial resection) are preferred for these tumors.