平坦・陥凹型早期大腸癌の内視鏡診断と治療―微小癌の内視鏡像を中心に

The Clinico-Pathological Features of Flat and Depressed Type of Early Colorectal Cancer

要旨　大腸には胃や食道と異なり，Ⅱb型やⅡC型早期癌はほとんどないとされてきた．しかし，その存在を十分に意識してtotal colonoscopyを行うことにより全腫瘍の3.5％に，早期癌の159％に平坦・陥凹型病変が発見された．Ⅱb 7病変，Ⅱc 13病変，Ⅱc＋Ⅱa 5病変であり，平坦・陥凹型の癌の頻度は51.0％と高かった．内視鏡像の特徴は，①淡い発赤，褪色で存在診断されることが多い，②空気変形を80％に伴う，③diffuseな発赤で辺縁不整を伴う，であり，微小癌は，①発赤不整，②微小陥凹，③褪色不整，④発赤類円形，の4型に形状分類された．実体顕微鏡所見では陥凹部に一致しfineな管状～類円形のpitの集合が特徴であり，ときに不整，無構造所見を認めた．10mm未満で，深い陥凹や強い空気変形を伴わない場合は，strip biopsyで治療が可能であった．平坦・陥凹型早期癌は従来考えられていたより多く存在することを強調した．

　Since April 1985, we observed 71 different lesions of flat and depressed type neoplatic lesions by endoscopic examination. We divided them into two different categories : early cancer (32 lesions) ; and tubular adenoma (39 lesions) .

　There were 23 lesions of non-elevated flat lesion (Ⅱb type), under 5 mm ; 7 of Ⅱb type early cancer. 14 of non-elevated depressed type (IIc type) were early type cancer, except one which was a different lesion. And all other lesions were depression-with-peripherally-elevated type (Ⅱc＋Ⅱa, Ⅱa＋Ⅱc).

　One characteristic effect of the visible manifestations of the flat and depressed type early cancer by endoscopic examination showed that the outside of the intes-tines can be stronger than the rising protuberance and the depressed part. Furthermore, the depressed part was emphasized by decreasing the air pressure inside of the intestines (air transformation) .

　The usual color of early cancer is a light red, but sometimes it can be seen as faded white. There was only one case in this series which was shown histologically to be early cancer. It was a case of poorly differentiated adenocarcinoma. All the others were cases of well defined adenocarcinoma. We pursued colon resection as the treatment in eight cases. However, mucosal carcinoma was treated with strip biopsy, in accord with the general practice.

　Using a dissecting microscope, we noticed the shape of tumors was circular, tubular and mixed, with a small pit pattern. Morever, it was observed that the surfaces were irregular and non-organized.