大腸早期癌の病理学的特徴―とくに組織発生的観点から

Pathological Characteristics of Colonic Early Cancers: From the viewpoint of histogenesis

　大腸の早期癌の定義は未だ定められていない．しかし胃早期癌にならって深達度sm迄にしようということが暗黙のうちの了解事項になっている感がある¹⁾．したがってここでは深達度smまでの癌を大腸早期癌と仮に定義して話を進めることにする．

　大腸早期癌の病理学的特徴を考える時，これと密接に関連して問題となることはその組織発生的特徴であろう．この問題を抜きにして大腸早期癌の病理学的特徴を論ずることは不可能である．組織発生的特徴とはいうまでもなく腺腫の癌化（adenoma-cancer sequence）である．大腸早期癌は腺腫（性ポリープ）と共存することがしばしばあることは経験上の裏づけである．大きい腺腫の一部に粘膜内癌があれば，これはまぎれもない大腸早期癌である．大腸早期癌というカテゴリーで症例を集めればかなりの率で腺腫内癌（cancerin adenoma）が含まれてくるのである．

　From the viewpoint of histogenesis, colonic early cancers should be classified as the following:

　a) Early cancer with adenoma

　b) Early cancer without adenoma (tous epithelium)

　c) Microcarcinoma

　We collected 25 lesions of colonic early cancer at the Fujieda General Hospital, including operation material and polypectomy material. Two lesions were excluded because of focal cancer (“atypia”) in adenoma. Of 23 lesions, 11 lesions-approxirnately half of the total lesions-contained adenoma or aden0matous epithelium, which indicated adenoma-cancer sequence. In addition, all of these 11 lesions except for 2 were accompanied by adenomas less than 2cm in diameter. This result suggests that most advanced cancers of the large intestine, resulting from a.den0macancer sequence, are originated from medium-sized or small adenomas, not from large adenomas.

　As for microcarcinomas less than 5mm in diameter, three lesions (3 mm, 2 mm and 800μ in diameter) were presented. Two of them, which were elevated lesions, showed co-existence of adenomatous epithelium and cancer. The other one, which were a depressed lesion, showed no accompanying adenomatous epithelium.

　The authors, however, would not consider the former two microcarcinomas as cancer arising from adenoma, but consider them as cancer produced by progression from benign-appearing epithelium (adenomatous epithelium) to malignant tissue. The authors maintain that cancerization by progression should be different from adenoma-cancer sequence.