大腸癌の自然史

Natural History of Colon Cancer

要旨　手術が行われたsm以深の大腸癌のretrospective study，生検でadenoma（一部cancerと診断されたものを含む）と，診断された5mm以上10mm未満の大腸ポリープ（Ⅰp，Ⅰsp，Ⅰs，Ⅱa）のfollow-up studyおよび実体顕微鏡による大腸正常粘膜の検索から次のような結果を得た．①smからsまたはaに達するのに約2年を要する．②mに存在する期間はかなり長く，数年を要する．③Ⅱb，Ⅱc，Ⅱc＋Ⅱa，Ⅱa＋Ⅱcなどの表面平坦，陥凹型から発育・進展するde novo carcinomaが大腸癌発生のメインルートであり，その早期のものはX線，内視鏡とも見逃されやすい．④いわゆるポリープ（Ⅰp，Ⅰsp，Ⅰs，Ⅱa）は発見されやすいが，10mm以上に増大するものは少なく，10mm未満の腺腫またはポリープは多数存在し，多発（同時性，異時性）するものが多く，ポリペクトミーの絶対的適応とはならない．

　Retrospective analysis of the invasive type colon cancer, follow-up investigation of the 5 to 10 mm sized adenomatous polyps confirmed by biopsy, and analysis of abnormal pit patterns of the normal mucosa of the colon by stereomicroscopic examination showed the following results.

　1) It may take about two years for invasive colon cancer to grow from the sm layer to s (the serosa) or a (the adventitia).

　2) Mucosal cancer may remain in the mucosa for several years or more.

　3) Only a few colon cancer may arise from adenoma, most of them were thought to be de novo carcinoma.

　4) Early shapes of de novo carcinoma were Ⅱb (surface flat) type and Ⅱc (surface depressed) type, which were easy to be missed by the radiological and endoscopic examinations.

　5) A de novo carcinoma typically developed into a submucosal tumor when invaded the sm layer, and type 2 or 3 macroscopic shape.

　6) A large majority of adenomas remained less than 10 mm in size, and a few of them may exceed 10 mm in size. Most of polyps were not indicated for polypectomy except for polyps larger than 10 mm in size or markedly deformed polyps.