通常内視鏡観察で深達度診断を誤診しEUSで正診しえたIIa型S状結腸癌の1例

A IIa Type Colonic Cancer that was Underdiagnosed by Conventional Colonoscopy, and Diagnosed by Endoscopic Ultrasonography, Report of a Case

要旨　症例は51歳，男性．主訴は下痢，便潜血反応陽性であった．大腸内視鏡検査にてS状結腸に管腔の約2/3周を占めるIIa型病変を認めた．通常内視鏡検査では病変中央に周囲よりやや丈の高い部分が存在したが，腫瘍の表面構造はほぼ保たれており，明らかなsm深部浸潤を疑う所見は認めなかった．注腸X線検査でも明らかな浸潤所見はみられなかった．しかし，超音波内視鏡検査にて病変中央部のやや隆起した部分に一致して腫瘍最深部が第4層に接しており深達度sm³と診断した．腹腔鏡下腸切除術を施行し，病理組織結果は高分化型腺癌，深達度sm³（垂直浸潤距離3,000μm），ly1，v0，n(－)であった．本例は通常内視鏡観察でsm深部浸潤を疑う所見が乏しく，sm浅層までの病変と考えられたが，超音波内視鏡にて深達度sm³と確診しえた．

　A 51-year-old male visited our hospital with diarrhea and positive indication of fecal occult blood. Conventional colonoscopy showed a IIa-type lesion, about 3cm in size, in the sigmoid colon. The center of the lesion was slightly protruded, but sm massive invasion was not suspected because the structure of the surface was almost perfectly preserved. Barium enema also showed no indication of submucosal massive invasion. Ultrasound endoscopy echo revealed the tumor had invaded the deepest layer of the submucosa (sm3). Laparoscopic partial colectomy was performed. Pathologically, the tumor was a well differentiated adenocarcinoma invading the deepest layer of the submucosa (sm3, ly1, v0, n0. The invasive depth was 3,000μm). This case is that of a colonic cancer that was underdiagnosed, using conventional colonoscopy as intramucosal or slightly submucosal invasion, but was diagnosed eventually by ultrasonography as massive submucosal invasion.

　1) Second Department of Internal Medicine, Osaka Medical College, Takatsuki, Japan