Crohn病関連消化管癌

Crohn's Disease-associated Intestinal Cancer

要旨●Crohn病の発症後長期経過例には消化管癌が発生し，本邦では直腸肛門管癌（痔瘻癌を含む）が半数以上を占める．粘液癌をはじめとする悪性度が高い組織型が多く，術前診断できない症例もあり，進行癌で診断され，予後は著しく不良である．予後改善には，早期発見と手術時の断端陰性の確保が重要と考えられる．欧米で推奨されている潰瘍性大腸炎と同様のサーベイランス内視鏡は，肛門病変合併例が多い本邦では施行困難な場合も多い．直腸肛門管癌の早期診断には発症後長期経過例を対象として，内視鏡検査の他にも麻酔下生検，分泌物の細胞診による病理組織診断や骨盤MRIあるいはCT，腫瘍マーカーの測定などを積極的に継続して施行することが重要である．

　Patients with longstanding Crohn's disease（CD）are at a high risk of developing intestinal cancers. In Japan, approximately 50% of intestinal cancers in patients with CD are located in the anorectal region. The incidence of highly malignant histological type is high, and the most prevalent histologic type of cancer is mucinous carcinoma. The prognosis is poor as the disease is frequently detected late and in the advanced stage. To improve the prognosis of intestinal cancer in patients with CD, early cancer detection and resection with negative surgical margin are imperative. Making surveillance colonoscopy—a common recommendation for patients with CD in Western countries—difficult for several patients with CD in Japan complicates anorectal diseases. The first step in detecting early stage cancer in the anorectal region includes histopathological examination of specimens obtained by endoscopic biopsy, examination of anal lesions under anesthesia, or cytology of anal fistula-derived secretion. Furthermore, pelvic computed tomography or magnetic resonance imaging and tumor marker measurement may aid in diagnosing early stage cancer. Proactively performing these examinations for longstanding anal lesions in patients with CD seems highly significant.