小さな表面型（Ⅱ型）大腸上皮性腫瘍―病理の立場から

Superficial-type Colorectal Carcinoma, Measuring below 1cm in Maximum Size: from the viewpoint of pathology

要旨　1cm以下の表面型粘膜内癌21病巣，sm癌7病巣，扁平腺腫39病巣の肉眼所見，実体顕微鏡観察による所見，病理組織学的所見を比較・検討し，これらの病巣の関連性について考察した．その結果，表面型（早期）大腸癌は高悪性度および低悪性度の早期癌に大別することが可能であり，①肉眼所見で粘膜表面に発赤を伴って陥凹を示す病巣は下方向への進展傾向が強く，高悪性度の早期癌に分類された，②実体顕微鏡観察で不規則溝紋型，不整型の表面微細構造を示し，軽度の陥凹を伴う病巣は高悪性度の癌と考えられた，③病理組織学的には粘膜深層において不整な分岐を示す腫瘍腺管により粘膜筋板の圧排・菲薄化を認める場合には高悪性度の粘膜内癌の可能性がある，④1cm以下のⅡa型粘膜内癌は，扁平腺腫と診断された病巣の一部およびⅡb型，Ⅱc型，Ⅱa＋Ⅱc型早期癌との問に形態学的な類似性を認め，進行大腸癌の前駆病変として注目すべきであろう．

　We have compared superficial-type colorectal carcinomas with small flat adenomas of the colon and rectum with regard to macroscopic, microscopic, and stereomicroscopic characteristics. We did this reviewing our own cases of colorectal carcinoma, which were resected by operation or endoscopic surgery in the last 12 years in our hospital.

　We have examined 21 lesions of superficial-type intramucosal carcinoma, 7 lesions of submucosal invasive carcinoma, and 39 lesions of flat adenoma below 1 cm in size, respectively.

　As a result of this research, we determined that it is possible to distinguish between superficial type colorectal carcinomas with high malignant potentiality and those with low malignant potentiality.

　We can distinguish the former from the latter in the following respects.

　1) We can classify, as carcinomas with high malig-nant potentiality those lesions which show slight depression associated with redness on the mucosal surface. This phenomenon tends to show downward growth.

　2) As a result of stereomicroscopical observation, we determined that carcinomas with high malignant potentiality show superficial minute irregularly grooved structure, or irregular shape with slight depression on the mucosal surface.

　3) Histopathologically, superficial type carcinomas, which show oppressed and thin mucosal muscular layer associated with irregular ramification of carcinomatous glands in the deep portion of the mucosa, can possibly be classified as intramucosal carcinomas with high malignant potentiality.

　We have concluded that it is worthwhile noting that there are morphological similarities between Ⅱa type intramucosal carcinomas below 1 cm in size and other superficial type neoplastic lesions, which are Ⅱb, Ⅱc, Ⅱa+Ⅱc type carcinomas, and are a part of “flat adenomas”, and therefore there is a possibility that these lesions are prototypes of ordinary advanced colorectal carcinomas.