胃カルチノイドの臨床診断

Diagnosis and Clinical Pathology of Gastric Carcinoid

　1907年，Oberndorferは小腸腫瘍のうちで，組織学的には癌ににているが，臨床的には良性の経過をとる病変を観察し，これをカルチノイド，carcinoidと呼んだ．その後の報告によると，カルチノイドは虫垂に最も頻度が高く，次いで小腸，直腸や胃にもみられているが，全体としては比較的，稀な疾患である．近年，カルチノイドはセロトニン（5-HT）を始めとして，ヒスタミンやカリクレインなどを産生する一種のfunctioning tumorであることが明らかとなって，病態生理学的にも注目されてきている．これらの物質の影響によって，臨床的にはいわゆるカルチノイド症候群，即ち，顔面及び四肢などの紅潮，即ちflush発作，下痢及び気管支喘息などがあげられており，臨床生化学的には血中5-HTの上昇，尿中5-HIAA（5-Hydroxy indole acetic acid）の増加を証明するとされているが，概して，胃カルチノイドにおいてはこれらの認められる頻度は少ないようである．病理組織化学的には銀親和性反応argentaffin reactionもしくは好銀性反応argentphilic reactionを認めることによっても診断される．

　近年，胃生検法の進歩によって，次第に手術前に胃カルチノイドの確診の得られた例が報告されてきている．胃カルチノイドの多くは緩徐の経過をとるものの，一部では肝転移を来して，予後の不良のこともあるので，臨床診断は慎重でなければならない．

　Including the 6 cases presented here, reported cases of gastric carcinoid in our country amount so far to 35. Chief complaints most often included abdominal pain with hematemesis and melena in 3 cases. The male outnumbered female with a ratio of 20 : 12. It was most frequently seen in the age groups 40～49 and 50～59. Mortality rate wate was 17.1 per cent (6 cases). In 7 out of 9 biopsied cases preoperative diagnosis was accurate; in the other 2 it was carcinoma. Of 18 cases biochemically examined, 3 showed increased level of 5-HT or 5-HIAA. Carcinoid syndrome was encountered in 3. The predilection sites of carcinoid were M, the lesser curvature and posterior wall. The largest lesion was 9.0 cm in diameter, and the greatest diameter measuring from 1.1 to 2.0 cm was most frequently seen (8 cases). We have classified the nature of the tumor surface into three types: smooth, eroded and ulcerating. In each of them 6, 5 and 16 lesions were demonstrated. The latter 2 types are most suitable for gastric biopsy.

　Higher levels of 5-HT in the blood and 5-HIAA in the urine were prerequisites for liver metastasis. A study of the relationship between the metastases to such organs as the liver, lymph nodes and peritoneum and the greatest diameter of carcinoid lesion as well as its ulceration shows that when a carcinoid tumor has either ulceration on the surface or when its greatest diameter exceeds 5 cm, metastases to the liver, lymph nodes, etc. are seen in higher rate and the prognosis is considered unfavorable. It is far better in cases where the tumor surface is smooth or the lesion is less than 5 cm in the greatest diameter.

　Inasmuch as gastric carcinoid chiefly develops in the submucosal layer, it is apt to be regarded as submucosal tumor by both x-ray and endoscopy. Inspite of its slow development, however, gastric carcinoid should be considered malignant. Meticulous planning for accurate preoperative diagnosis is therefore in order with biopsy as its chief armamentarium.