短期間に形態変化を来した早期大腸癌の1例

Mucosal Cancer of the Sigmoid Colon Transforming from a Sessile (so called Is＋IIc) to a Superficial Depressive Lesio n (IIc＋IIa), Report of a Case

要旨　症例は59歳，男性．便潜血反応陽性を指摘され当院を初診した．大腸内視鏡検査でS状結腸に約6mm大の隆起性病変を指摘された．病変の立ち上がりは正常粘膜であり，淡く発赤した陥凹局面と陥凹内結節を認め，いわゆるIs＋IIc型形態を呈していた．陥凹内の微細表面構造観察でも乱れはあるものの無構造部分は認められなかった．約3か月後の内視鏡検査では大きさに変化はないものの陥凹内結節はやや縮小かつ減高していた．また微細表面構造に変化は認めなかった．さらに3週間後には陥凹が深くなりIIc＋IIa型へと変化していた．深達度sm深部浸潤癌と診断し腹腔鏡補助下S状結腸切除術を施行した．病理組織学的には高分化型腺癌が粘膜筋板を押し下げるように粘膜深部に発育していたが，粘膜筋板は保たれており間質反応も認められず深達度はmと診断した．大きな形態変化を来しながら最終的にm癌であった症例はまれであり報告した．

　A 59-year-old male was admitted to our hospital for further examination because of positive testresults for IFOBT. Colonoscopy showed a sessile protrusion with a depressed area on its surface which is so the called type Is＋IIc. Magnifying endoscopy showed type VI pit pattern of the protrusion in the depressed area and type IIIL pit pattern of the depression. Normal pit pattern was detected on the surface of the marginal elevation. After EUS examination, the depth of invasion was estimated as sm massive. Almost three months later, colonoscopy showed a superficial depressed type (IIc＋IIa). Laparo-assisted sigmoidectomy was performed and the resected specimen proved to be a lesion of type IIc＋IIa resembling the sucler of an octopus. Histological section revealed, under a thin muscularis mucosae, a well differentiated adenocarcinoma extending towards the submucosal layer and hemosiderin. The depth of invasion was finally determined as m. We, therefore, guess that our case was transformed because of initial relaxation of the musclaris-musosa and vermiculation of the colon.

　1) Department of Gastroenterology, Watari Hospital, Fukushima, Japan

　2) Department of Pathology, Watari Hospital, Fukushima, Japan