内視鏡所見と実体顕微鏡所見からみた陥凹型早期大腸癌の診断

Diagnosis of Depressed Type Early Colorectal Cancers from the Endoscopic and Pathological Point of View

要旨　陥凹型早期大腸癌の特徴を明らかにする目的で表面陥凹型早期癌44病変（m癌33病変，sm癌11病変）を対象とし，その内視鏡像，実体顕微鏡および病理組織学的所見について検討した．陥凹型は5mm以下よりsm癌が存在し，他形態の早期癌と比較した場合sm癌の占める割合とその深部浸潤度が極めて高く，臨床的には小サイズ（10mm以下）での発見が必要であった．陥凹底部の凹凸不整や陥凹部における不整・無構造なpitの存在はsm massive癌を強く示唆する所見であり，陥凹表面の観察はsm浸潤度診断に有用と思われた．内視鏡的に褪色調を呈する腫瘍の多く（80.0％）は非腫瘍部にmelanosisを有していた．大腸進行癌への発育・進展上，絶対および相対陥凹型はいずれの形態も重要な初期病変と考えられる．

　We studied endoscopic and microscopic features of superficial depressed type early colorectal cancer in 44 lesions. They included 33 mucosal invasive lesions and 11 submucosal invasive lesions.

　Superficial depressed type early colorectal cancers may have submucosal invasion even in the lesion smaller than 5 mm in size. Compared to other type of early colorectal cancers, depressed type has higher incidence of submucosal invasion and deeper invasion to the underlying layers. Therefore, it is clinically important to detect the lesions while they are less than 10 mm in size.

　Irregularity or irregular and/or amorphous pit pattern on the floor of the depressed lesion strongly suggests extensive submucosal invasion. It is useful to observe carefully the floor of the depressed lesion for the diagnosis of submucosal invasion. Most of the cases (80%) which had whitish discolored and depressed lesions had melanosis in non-cancerous area.

　Not only absolutely but also relatively depressed type lesions may be important as initial lesions which would develop into advanced colorectal cancers.