微小早期大腸癌（5mm以下）の内視鏡学的，組織学的検討

Endoscopic and Histopathological Study of Diminutive Carcinomas (5 mm or less in Diameter) of the Large Bowel

要旨　5mm以下の大腸癌を“微小大腸癌”と定義することを提唱した．自験9例の微小大腸癌（m癌8例，sm癌1例）を内視鏡学的，組織学的に検討し，次のような結果を得た．（1）微小癌の分布は直腸に3例と最も多く存在し，次いでS状結腸，上行結腸の2例，横行結腸，盲腸1例の順であった．右側結腸にも3例，33.3％存在したのは注目される．なお4例，44.4％は微小癌以外にも隆起性病変がみられ，うち2例は早期癌（m癌）が1病変ずつ認められた多発癌例であった．（2）9例すべてが隆起性病変であり，平坦型ないし陥凹型の病変は認められなかった．隆起の形態は無茎性（扁平に近いのも含む）5例，亜有茎性3例，中心陥凹を伴うⅡa＋Ⅱc型が1例であった．内視鏡的には4例に退色調，血管拡張模様，出血，緊満性，充実性がみられたが，積極的に悪性を示唆する所見ではなかった．しかし1例は，頂部が決壊し白苔を伴う潰瘍面を形成し，その辺縁は不規則で発赤もみられ，明らかな悪性所見を示した．残りの4例は何ら特徴的所見はなく，切除し組織学的検索後初めて悪性と診断された．（3）組織学的には，いずれも分化型腺癌であった．carcinoma in adenomaが4例で最も多く認められ，adenoma in carcinoma3例，polypoid carcinomaは2例の順であった．深達度に関しては8例（88.9％）が粘膜内に止まっており，1例（11.1％）のみが粘膜下層に腺癌のmassive invasionが認められた．

　Nine diminutive early carcinomas (0.35％) out of 2,540 colonic polyps were identified and removed endoscopically during the past four year and two months. Three of these were located in the sigmoid colon, two each in the rectum and the ascending colon, and one each in the transverse colon and the cecum. Four cases (44.4％) were accompanied by other elevated lesions including focal carcinomas in two cases. All lesions were classified into protruded type. In four cases were discoloration, capillary dilatation, bleeding and significant hardness observed endoscopically on the polypoid lesion. An irregular ulceration with white coat suggestive of malignancy was noted on the top of the lesion in only one case. The rest of the cases did not appear malignant endoscopically, but were shown later to have carcinoma by histological examination. Histopathology showed well differentiated adenocarcinoma in all cases; carcinoma in adenoma in four cases; adenoma in carcinoma in three cases; carcinoma de novo in two cases. Carcinomatous invasion was limited to the mucosal layer in eight cases (88.9％) and seen massively in the submucosa in one case. There was neither lymphatic nor venous infiltration in any cases.

　In conclusion, even in cases of diminutive polyps (5 mm or less in diameter) carcinomas were recognized endoscopically. Furthermore, both carcinomas accompanied by adenoma and carcinomas de novo were shown to exist.