十二指腸腫瘍および腫瘍様病変―文献的考察

Duodenal Tumour and Tumour: like Lesion, a Review of Literatures

要旨　十二指腸腫瘍および腫瘍様病変は比較的まれで，X線検査や内視鏡検査が進歩・普及し，十二指腸が胃の次に位置する臓器でありながら，食道・胃・大腸などほかの消化管の腫瘍に比べ，臨床的になじみの薄い疾患と言えよう．十二指腸腫瘍および腫瘍様病変は，症状を有する古典的な腫瘍，検査で偶然発見される小病変，免疫組織学的に同定される内分泌細胞腫瘍の3つに大別できる．われわれは，この観点から，十二指腸腫瘍および腫瘍様病変を分類し，頻度を中心とした一般的事項を検討した．小腸全体でみると，小腸腫瘍自体が少なく，非上皮性腫瘍の占める割合が大きく，欧米に比べカルチノイド腫瘍が少ない．十二指腸癌はX線・内視鏡検査の普及により，乳頭上部の癌，特に早期癌の発見が増えており，早期癌では下行部より球部に多いことがわかった．更に，十二指腸腫瘍および腫瘍様病変をめぐって，十二指腸腫瘍が少ない理由，十二指腸癌の組織発生，十二指腸乳頭部癌の取り扱い，カルチノイド腫瘍といった問題について考察した．十二指腸腫瘍が少ない理由として，小腸の解剖・生理学的および免疫学的要因，小腸の発生・分化の関与などが示唆された．カルチノイド腫瘍は内分泌細胞腫瘍をめぐる概念の認識がまず必要であり，早期癌を含む他の十二指腸小病変と同様，丹念な内視鏡検査や免疫組織化学検査の普及によって，新しい知見，認識が得られるであろうことを述べた．

　Duodenal tumour and tumour-like lesion (duodenal tumours, for brevity) are relatively rare. Although radiological and endoscopic examinations have become popular and the duodenum is the segment next to the stomach, we are not so familiar with the duodenal tumours as those of the oesophagus, stomach and colon. Duodenal tumours may be devided in the following 3 categories: Classical symptomatic tumours, small asymptomatic lesions found by examinations, and endocrine cell tumours identified by immunohistochemical studies.

　With this classification, we discussed the general issues including the incidence. When the small intestine is viewed as a whole, small intestinal tumours are uncommon, in which non-epithelial tumours are predominant; compared to Europe, carcinoid tumours are less frequent in Japan. In duodenal carcinoma, those proximal to the duodenal papilla, particularly early carcinoma, are increasing, following the diffusion of radiological examination and endoscopy; early carcinoma is more frequent in the duodenal bulb than in the descending part.

　Furthermore, we discussed the reasons for low incidence of duodenal tumours, histogenesis of duodenal carcinoma, how to deal with carcinoma of the duodenal papilla and carcinoid tumour of the duodenum.

　Low incidence of duodenal tumours seems to be related to anatomical, physiological and immunological factors involving the small intestine and to the development and differentiation of the small intestine.

　Regarding carcinoid tumour, the concept of endocrine cell tumour should first be recognized. Similar to other small lesions including early carcinoma, careful endoscopy and more frequent use of immunohistochemistry will lead to new findings.