進行大腸癌の初期病変としての大腸“表面型”病変の意義

Significance of Superficial Epithelial Lesions as Lesions Preceding Advanced Colo-rectal Cancers

要旨　進行大腸癌の初期病変と関連して重要視されている“表面型”病変につ

いて検討を行った．切除標本の組織学的検討から，進行大腸癌の8～9割は扁平隆起由来，1～2割は平坦・陥凹型早期癌由来であることが推測された．進行癌に発育する有茎性病変は少ないと思われた．検診受診者6,771名における“表面型”病変の有病率は1.0％で，その中の癌の割合は11.8％であった．われわれの施設で発見した“表面型”病変165病巣の形態は，Ⅱa 97.6％，Ⅱa＋Ⅱc 2.4％であった．純枠なⅡcは認めなかった．大腸癌による死亡を減少させるには，“表面型”病変の存在の可能性を常に，頭に置いて注意深く注腸X線もしくは大腸内視鏡検査を行うことが重要である．

　From April, 1983 to August, 1989, we studied colorectal neoplasms found at our hospital to see what lesion precede advanced colo-rectal cancers. Pathological study of 205 advanced colo-rectal cancers suggested that 80 to 90% of them developed from superficially elevated lesions, and 10 to 20% developed from flat or superficially depressed lesions. It was indicated that only a few advanced color-rectal cancers developed from pedunculated lesions. Epidemiological study of 6,771 patients who first received colonoscopies for screening of colo-rectal cancers revealed that there were 68 cases (1.0%) with superficial epithelial lesion, including superficially elevated, flat and superficially depressed lesion. Endoscopic study on macroscopic types of 165 superficial epithelial lesions revealed that 97.6% of them were Ⅱa, and 2.4 % were Ⅱa+Ⅱc. There were no lesions which were purely Ⅱc. These results suggest we may have missed quite a lot of flat or superficially depressed early colo-rectal cancers so far. In order to decrease the death rate caused by colo-rectal cancer, it is very important to do barium enema or colonoscopy carefully, keeping in mind the possibility of the existence of superficial epithelial lesions.