通常内視鏡による潰瘍性大腸炎関連腫瘍診断の現状と課題

Current Status and Problems of the Diagnosis of Ulcerative Colitis-associated Neoplasia on Conventional Endoscopy

要旨●潰瘍性大腸炎関連腫瘍（UCAN）の通常内視鏡診断について検討した．対象はUCAN 67病変で，内訳はcolitic cancer 38病変，dysplasia 29病変である．UCANを発見する契機となった通常内視鏡所見は，限局性の隆起や発赤が多く，診断には色素内視鏡観察の併用が有用であった．UCANの肉眼型は隆起型が多いが，dysplasiaでは平坦型も認められた．通常内視鏡所見では，UCANは発赤調を呈する病変が多かった．腫瘍の境界が不明瞭な病変はcolitic cancerの61%，dysplasiaの34%を占め，UCANの特徴的所見であると考える．UCANの中でcolitic cancerの多くは通常内視鏡検査で診断可能と考えられるが，平坦型の病変は存在診断さえ難しい場合がある．通常内視鏡所見で，UCの罹患範囲に限局性の隆起や色調変化，凹凸不整や陥凹などが観察される場合は色素内視鏡観察を行い，積極的な狙撃生検を行うことがUCANの診断に必要であると考える．しかし通常内視鏡検査では診断困難な病変や，sporadicに発生する腫瘍との鑑別が難しい病変があることを認識しておく必要がある．

　In this study, we used conventional endoscopy for the diagnosis of UCAN（ulcerative colitis-associated neoplasia）. We reviewed 67 lesions of UCAN, 38 lesions of colitic cancer, and 29 lesions of dysplasia. The main findings using conventional endoscopy for detection of UCAN included presence of localized protrusions or redness. Furthermore, the concurrent use of chromoendoscopy was useful in the diagnostic process. Regarding the macroscopic type, majority of UCAN cases were of elevated type, and some cases of dysplasia were of flat type. Overall, 61% cases of colitic cancer and 34% cases of dysplasia were poorly demarcated, suggesting a characteristic finding of UCAN. Therefore, conventional endoscopy can identify several cases of colitic cancer from the respective UCAN lesions. On the other hand, the identification of flat-type lesions is quite difficult. Conclusively, when conventional endoscopy identifies characteristic findings, such as localized elevation, changes in color, surface irregularities, and depression in a site affected by UC, chromoendoscopy with target biopsy can subsequently facilitate and validate UCAN diagnosis. However, it is imperative to identify and locate the lesions that are difficult to diagnose using conventional endoscopy but also the lesions that are difficult to distinguish from sporadic adenoma and carcinoma.