微小Ⅱc型早期大腸癌の1例

Ⅱc (depressed) Type Early Carcinoma of the Descending Colon, Report of a Case

要旨　早期大腸癌の肉眼形態は隆起型がほとんどであり，ⅡcあるいはIlb型の報告は非常に少ない．われわれは下行結腸に発生した4mmのⅡc型sm癌を経験したので報告する．患者は50歳，男性．CEA4.1ng/dlとやや高値のため全大腸ファイバースコープ検査を施行し，下行結腸に異常なdiffuseな発赤を認め，空気量を変化させることにより浅い陥凹性病変(Ⅱc)と判断し生検を行った．その結果，腺癌と診断され腸切除を施行した．切除標本では粘膜ひだの集中断裂を伴うⅡc病変であり，組織学的にはわずかにsmに浸潤する高分化腺癌であった．腺腫成分は認められず，de novo癌と考えられた．内視鏡医は発赤で発見されるこのような病変を念頭において注意深く検索する必要があると思われた．

　There have been only a few reports on the superficial depressed (Ⅱc) type early colorectal cancer with its histogenesis and developmental process being totally unknown.

　A 50-year-old man underwent total colonoscopy examination because of high CEA, i.e., 4.1ng. A depressed lesion with redness, measuring 4×4mm, was found in the descending colon. There also was a flat elevated type (Ⅱa) lesion, measuring 5×5mm, in the transverse colon.

　A biopsy specimen taken from the depressed lesion in the descending colon showed adenocarcinoma, while a hot biopsy specimen taken from the flat elevated lesion in the transverse colon showed carcinoma in adenoma. Under these pathological diagnosis, colectomy was carried out.

　Histological examination of the lesion showed well differentiated adenocarcinoma with submucosal invasion (sm_1a). Adenomatous change, however, did not exist in the lesion.

　It is yet to be known whether the incidence per se of this type of colorectal cancer is truly low or diagnostic ability is simply low in detecting this type of cancer.

　This case implicates that superficial depressed cancer should be among the differential diagnosis of red lesion of the colon.