直腸・肛門管における腫瘍性疾患の内視鏡診断

A Review of the Endoscopic Diagnosis of Neoplastic Lesions in the Rectum and Anal Canal

要旨●直腸・肛門管領域の腫瘍性疾患は多彩であり，直腸癌や肛門管癌に加えて，神経内分泌腫瘍（NET），悪性黒色腫，GIST，悪性リンパ腫などが含まれる．直腸NETは内視鏡検査でしばしば偶発的に発見される重要な疾患であり，正確な質的診断と深達度評価が治療方針の決定に直結する．一方で，悪性黒色腫やGISTなどの希少腫瘍は診断に難渋することが多い．これらの多様な疾患群において，内視鏡診断は病変の早期発見から治療戦略構築まで不可欠な役割を担う．通常観察（白色光）に加え，色素内視鏡や拡大内視鏡，超音波内視鏡検査（EUS）を組み合わせることで診断精度が向上し，より適切な治療選択につながる．本稿では直腸・肛門管における腫瘍性疾患の内視鏡所見を整理し，その診断上のポイントと臨床的意義を概説する．

　Neoplastic diseases of the rectum and anal canal comprise a wide spectrum of conditions, including rectal adenocarcinoma, anal canal carcinoma, neuroendocrine tumors（NETs）, malignant melanoma, gastrointestinal stromal tumors（GISTs）, and malignant lymphoma. Accurate assessment is essential in determining appropriate treatment strategies for rectal NETs, which are relatively common lesions that are incidentally detected during colonoscopy. In contrast, rare tumors, such as malignant melanoma and GISTs, frequently pose diagnostic challenges. Endoscopy plays a central role in the early detection and clinical management of these diverse neoplastic diseases. Conventional white-light endoscopy used in combination with adjunctive techniques, such as chromoendoscopy, magnifying endoscopy, and endoscopic ultrasonography（EUS）, improves diagnostic accuracy and supports therapeutic decision-making. This review summarizes the endoscopic diagnostic features of neoplastic diseases of the rectum and anal canal and highlights their clinical relevance.