4) 内分泌細胞腫瘍（カルチノイド，内分泌細胞癌）

Small Bowel Carcinoid

要旨　小腸カルチノイドは欧米に比し本邦では比較的まれな疾患であるとされている．これまでは部位的な問題から早期発見が困難で，進行した状態で発見されることが多かった．しかし，近年のダブルバルーン小腸内視鏡，カプセル内視鏡などを用いた小腸疾患に対する診断能の目覚ましい進歩により，今後は早期の段階で小腸カルチノイドに遭遇することが予想される．そのため小腸カルチノイドの臨床像を正確に認識しておくことが必要である．本稿では，過去の本邦報告例を検討し，小腸カルチノイドの臨床像（発生部位別頻度・転移率），画像診断の特徴などを概説し，新しい小腸内視鏡を用いた本疾患の取り組みかたについて述べる．

　Small bowel carcinoid is a rare disease in Japan, compared to Western countries. The preoperative diagnosis of small bowel carcinoid has been difficult so far, because standard imaging techniques, such as colonoscopy and small-bowel barium contrast studies, rarely identify the primary small bowel carcinoid. Because of this, many cases were diagnosed from major symptoms or by resected specimens of small bowel tumors.

　Recently, the double-balloon small intestine enteroscope and the capsule endoscope have been introduced and have markedly advanced the diagnosis of small bowel disease. Therefore, it is necessary to recognize the clinical characteristics of small bowel carcinoid accurately. In this article, we described specific clinical features of small bowel carcinoids.

　In general, small bowel carcinoids can be characterized as having slow or indolent growth. They are often located very close to the ileocecal valve. Accordingly, careful examination of the ileum by colonoscopy has been useful in the detection of primary carcinoid tumors in the ileum. Tumor size is an unreliable predictor of metastatic disease. The metastases, to the lymph node or liver, have been reported even from tumors measuring less than 10 mm in diameter. Moreover, surgical management of small bowel carcinoids and also synchronous tumors requires wide resection together with complete resection of the supporting mesentery and lymph nodes, because small bowel carcinoid mostly develops multicentrically.

　In the future, pre-operative double-balloon enteroscopy and capsule endoscopy will be useful for investigating other lesions in the small bowel.