S状結腸表面型serrated adenomaに合併した粘膜内癌の1例

Superficial Serrated Adenoma with a Minute Early Carcinoma in the Sigmoid Colon, Report of a Case

要旨　症例は61歳，女性．大腸X線検査ではS状結腸に結節集簇様・平盤状の隆起を認めた．内視鏡検査では，全体に白色調の扁平な隆起で表面に，発赤，出血，陥凹はなく中央部にやや丈の高い結節状の部分を認めた．拡大内視鏡では，表面は細顆粒状で，II型に類似したpitが認められた．生検でserrated adenoma（SA）と診断，腹腔鏡下S状結腸切除術を施行．切除標本は，35×32mmの丈の低い，類円形，白色調の結節集簇様病変であった．実体顕微鏡観察では，病変全体は星芒状のII型pit，やや丈の高い部位はシダの葉様III型pitの部分より構成され，病変中央部には，V_I型と考えられる部位が認められた．病理組織診断では，全体に腺管は鋸歯状で，基底膜に接した腺底部では核の大型化，多層化もみられSAと診断した．また病変中央付近の径3mmの表面粗ぞう部で，核が粗大化し腺管の構造異型も著しい粘膜内癌を認めた．Ki-67（MIB-1）染色では癌部，腺底部に一致し陽性細胞が認められた．p53染色では癌の部分のみがびまん性に陽性となった．本例は表面型SAに合併した粘膜内癌と考えられた．

　We have excountered an early colon carcinoma arising on a mixed hyperplastic adenomatous polyp called a serrated adenoma.

　A 61-year-old asymptomatic female underwent a barium X-ray examination of the colon because of positive fecal occult blood. A shallow elevated round polyp about 30mm in diameter was seen in the middle sigmoid colon. This lesion appeared to be a granular aggregated-type polyp. Endoscopical examination revealeded a flat, whitish, and round polyp. Biopsied specimens showed adenoma, and laparoscopical partial sigmoidectomy was performed.

　A flat round shallow elevated lesion 35mm in diameter was operated on. Dissecting microscopy showed a large pit pattern on most of the lesion except for an irregular pit pattern in the middle. Histopathological study showed serrated glands with atypical nucleus changes in the lesion. We diagnosed this lesion as serrated adenoma. In adition, well differentiated adeno-carcinoma component 3mm in diameter was detected in the shallow elevated nodular part of the lesion. Carcinoma was observed to be limited to the mucosa. p53 staining showed diffuse positive cells only in the carcinoma. Ki-67 staining positive cells were observed in the lower part of the serrated glands and the whole of the actual carcinoma. We diagnosed this lesion to be an early colon carcinoma arising in a serrated adenoma.