経時的変化を追えたSSA/P（sessile serrated adenoma/polyp）由来早期大腸癌の1例

Sessile Serrated Adenoma/Polyp Developing into Early Colonic Carcinoma, Report of a Case

要旨●患者は70歳代，女性．下部消化管内視鏡検査にて，上行結腸に径7mm大の0-IIa型病変を認めた．表面に強固な粘液の付着を認め，インジゴカルミン色素撒布像では，大部分に開II型pitを認めた（後に，この病変がSSA/Pと判明）．しかし，結腸内に他に病変が多発しており，他病変と併せて厳重に経過観察する方針とした．14か月後に再検したところ，同病変は肉眼型が0-Is＋IIa型に変化していた．腫瘍の大部分でV_I型pitを呈しており，粘膜内癌が疑われたため，EMRを施行した．病理診断は，papillary adenocarcinoma with SSA/P，Tis（M），ly0，v0であった．SSA/Pから癌化したと考えられた1例で，表面構造の変化も含め，経過を追えた興味深い症例であった．

　A woman in her seventies was admitted to our department for the screening of colon cancer. Colonoscopy findings revealed a type IIa lesion, 7mm in diameter, in the ascending colon. The lesion was noted to have copious amounts of surface mucous. A chromoendoscopic view with an indigo carmine dye revealed type II open pit patterns over most of the lesion. On the basis of our findings, the lesion was diagnosed as a SSA/P（sessile serrated adenoma/polyp）. We decided to closely monitor the patient mainly because of the presence of numerous other polyps in her colon. After 14 months, a repeat colonoscopy revealed significant changes to the lesion, which were noted to be type Is＋IIa. Magnifying observation with crystal violet dyeing revealed type VI pit patterns over most of the lesion. On the basis of our findings, this lesion was diagnosed as an early colonic carcinoma that had invaded the mucosal layer. We treated this lesion using endoscopic mucosal resection. A histopathological examination revealed a papillary adenocarcinoma with SSA/P, Tis, ly0, and v0. It was thought that this lesion was an early colonic carcinoma that had developed from SSA/P.