大腸鋸歯状腺腫の内視鏡診断

Colonoscopic Diagnosis of Serrated Adenoma

要旨　過去3年間に経験した大腸鋸歯状腺腫（serrated adenoma；SA）の内視鏡所見と組織所見を検討し以下の結果を得た．(1)全53病変のうち36病変（68％）が直腸・S状結腸に存在し，有茎性ないし亜有茎性の隆起性病変が34病変（64％）を占めていた．(2)53病変はその表面構造から過形成様（H群）17病変，脳回様（C群）18病変，両者を有する混合型（M群）18病変に分類可能であった．(3)内視鏡的に切除された30病変を腺腫の診断基準に準じて分類すると，腺管状10病変（33％），腺管・絨毛状14病変（47％），絨毛状6病変（20％）で，高度異型を4病変に認めた．(4)同30病変の表面構造と組織像の対比では，H群（11病変）では腺管状が91％であったのに対し，C群（8病変）とM群（11病変）では全病変に絨毛成分が認められ，C群の1病変とM群の3病変が高度異型を呈した．以上から，SAは遠位大腸に隆起性病変として好発し，表面構造が特徴的であること，および癌ないし絨毛腺腫への進展が示唆されたが，臨床的には通常腺腫と同等に取り扱って問題ないと考えられた．

　The aim of this study was to clarify colonoscopic features of serrated adenomas. Endoscopic findings of 53 serrated adenomas of the colorectum were investigated with respect to location, configuration and histologic findings. The serrated adenomas were located predominantly in the distal portion of the colorectum, and they frequently manifested pedunculated or semi-pedunculated configuration. Their surface features determined under colonoscopy could be divided into either hyperplastic pattern, cerebriform pattern or mixed pattern. Tubular type of serrated adenoma was predominant in the hyperplastic pattern, while tubulovillous or villous type of adenoma was frequent in the cerebriform pattern and in the mixed pattern. High grade dysplasia was found in three of 11 lesions with mixed pattern, while it was found in one of 11 lesions with hyperplastic pattern and in none of eight lesions with cerebriform pattern. These findings suggest that 1) surface features in serrated adenoma have close correlation with their histologic type, and 2) they provide important information for endoscopic diagnosis of this type of colorectal neoplasia.