陥凹内隆起様形態を呈した表面型大腸腺腫の2例

Flat Adenoma with Central Elevation Suggesting Submucosal Invasion, Report of Two Cases

要旨　〔症例1〕は76歳，男性．下腹部痛のため内視鏡検査を施行．S状結腸に径4mmの陥凹内隆起を伴う陥凹型病変を認めた．拡大観察で陥凹部にⅢs型pitを認め，内視鏡的粘膜切除術（EMR）を施行した．組織学的には中等度異型腺腫であり，粘膜筋板の挙上による隆起であった．〔症例2〕は70歳，女性．下血のため内視鏡検査を施行．S状結腸に7mm大の陥凹内隆起を呈する病変を認めた．EMR後の実体顕微鏡観察では全体がⅢL型pit，組織学的には軽度異型腺腫であり，粘膜筋板の局所的な挙上による隆起であった．2症例ともに，陥凹内隆起の内視鏡所見より粘膜下層深部浸潤癌を疑ったが，拡大観察により粘膜内病変の診断が可能と考えられた．

　We present 2 cases of flat adenoma with central elevation, suggesting submucosal invasion in ordinary colonoscopy. Case 1: a 76-year-old male complaining of lower abdominal pain underwent colonoscopy. Colonoscopy revealed a depressed lesion with central elevation, measuring 4 mm in the sigmoid colon. On magnified view, Ⅲs pit pattern was observed in the central elevated area. Endoscopic mucosal resection was performed, and histology revealed a tubular adenoma with moderate atypia. Case 2 : a 70-year-old female underwent colonoscopy for further examination of a melena. Colonoscopy revealed a seemingly depressed lesion with central elevation, measuring 7 mm in the sigmoid colon. The margin of the depressed area was clear throughout most of the circumference, but unclear in parts. Endoscopic mucosal resection was carried out. Dissecting microscopy revealed ⅢL pit pattern in almost the whole area of the lesion. Histology showed a tubular adenoma with mild atypia. In past reports, it has been suggested that“central elevation in a depressed area” means massive invasion of the submucosal layer. This phenomenon was observed in the present two lesions, however, these lesions were adenomas. From this we can conclude that such lesions are not necessarily to be diagnosed as submucosal carcinoma and magnifying colonoscopy can be used to diagnose them correctly.