5mm以下の大腸微小腺腫の診断と取り扱い―見つけ出しと取り扱い

Diagnosis and Treatment for Minute Adenomas 5 mm or Less in Size Detection and Management

要旨　1991年4月から1995年3月までに発見，治療した5mm以下の大腸微小病変は1,090例1,830病変で，同時期に治療した大腸病変の48％に相当した．肉眼型別では，隆起型ではIsが890病変，Ispが516病変，Ipが88病変であった．これら隆起型病変のうち内視鏡的に処置された過形成は計337病変(22.6％)と高頻度であった．また癌の頻度は1.1％と低かった．表面型では表面隆起型が276病変と表面型微小病変の大多数を占めたが，過形成の頻度は68病変(24.6％)，癌の頻度も2.2％であり，表面隆起型の微小病変は隆起型病変とほぼ同様の傾向を示した．一方，表面陥凹型のIIcは51病変，IIa＋IIcは9病変であり，これらでは病変数は少ないものの過形成は1病変(1.7％)と隆起型，表面隆起型に比較して有意に低く，癌の頻度も20％と有意に高かった．また，同一肉眼型における微小腺腫と微小癌の臨床的鑑別は困難であった．以上から，5mm以下の微小病変のうち隆起型すべてと表面隆起型のIIaについては，積極的な内視鏡的治療は行わずに生検の結果で処置すべき病変を選択すべきと思われた．一方，表面陥凹型のIIc，IIa＋IIcは生検にとどめずに，発見時に積極的に内視鏡的治療を行うべきと考えられた．

　Between April, 1991 and March, 1995, 1,830 colorectal minute lesions in 1,090 cases were detected and treated by colonoscopy and made up 48% in all colorectal lesions treated during the same period. These minute lesions were classified according to the criteria of macroscopic type: 890 lesions of type Is, 516 lesions of type Isp, 276 lesions of flat elevated type (type IIa), 88 lesions of type Ip, 51 lesions of flat depressed type (type IIc) and 9 lesions of flat elevated with depression type (type IIa+IIc). In protruded types of Ip, Isp and Is, hyperplastic lesions (non neoplastic lesions) were encountered in 337 lesions (22.6%), whereas cancer was infrequent at incidence of 0.6%, 1.2%, 4.5%, in each macroscopic type. Moreover, minute flat elevated type (type IIa) also had a high rate of the hyperplastic lesions (68 lesions, 24.6%) but a low rate of cancer-like protruded minute lesions (6 lesions, 2.2%). On the contrary, type IIc and type IIa+IIc had a low rate of hyperplastic lesions but cancer rate was high at 21.6%, 11.1% in each type compared with other types of colorectal minute lesions. It was difficult to distinguish intramucosal carcinomas and adenomas in each macroscopic type by x-ray and colonoscopic examination.

　Thus, we recommend as an initial management to perform only biopsy for minute protruded types of Ip, Isp, Is and minute flat elevated type of IIa rather than carry out endoscopic treatment such as polypectomy and endoscopic mucosal resection (EMR). They also say that endoscopic resection immediately after detection is mandatory in flat depressed types of IIc and IIa+IIc.