inverted growth patternを示した陥凹型大腸癌の1例

Depressed-type Early Colon Carcinoma Presenting Inverted Growth Pattern, Report of a Case

要旨　患者は51歳，男性．便潜血反応陽性．大腸内視鏡検査にて，S状結腸に深い陥凹を有する約10mmのIIa＋IIc型病変が認められた．拡大観察では，陥凹面はIIILおよびIIIs型pitで占められ，生検部位でVI pitが認められた．粘膜内病変と判断し内視鏡的粘膜切除を施行した．病理学的には高度異型腺腫を伴う高分化型腺癌で，陥凹部で粘膜下層側へ深く侵入する像が認められた．腫瘍腺管は粘膜筋板を押し下げるように発育し，先進部においても部分的に粘膜筋板が認められた．先進部周囲の間質は粘膜内のものと同様であり，desmoplastic reactionを伴っていなかった．以上より，本病変はinverted growthにより深い陥凹を示したが，本質的にはそのほとんどが粘膜内の病変と考えられた．

　A 51-year-old man underwent colonoscopy for further examination for positive fecal occult blood. A IIa＋IIc type lesion measuring 10 mm in diameter was detected in the sigmoid colon. Although there was a deep central depression, other findings of submucosal invasion were not observed. Under magnifying colonoscopy, the surface of both the depressed area and the marginal elevated lesion showed IIIL or IIIS pit patterns. VI pit pattern was not observed except in the area of the previous biopsy. VN pit pattern was not observed. We considered that the lesion was limited to the mucosa without invasion of the submucosa, and endoscopic mucosal resection was successfully carried out. The lesion was histologically diagnosed as a well-differentiated adenocarcinoma associated with adenomatous glands. The center of the tumor deviated toward the submucosa, but the lamina propria of the mucosa was present in the area deviating into the submucosa. Fragments of muscularis mucosae were observed around the deep margin of the lesion, although some parts of them were unclear. There was no desmoplastic reaction. These findings suggested that this lesion showed an endophytic and expansive growth of the musocal component into the submucosa. We diagnosed this lesion as colorectal carcinoma with minute submucosal invasion, but we consider that, basically, it had biological behavior similar to that of a mucosal carcinoma.

　1) Department of Surgery, Jichi Medical School, Tochigi, Japan

　2) Department of Surgery, Omiya Medical Center of Jichi Medical School, Saitama, Japan