大腸微小腺腫の自然史

Natural Course of Diminutive Colorectal Adenoma

要旨　(1)腺腫は放置すると，①癌化するか，②そのまま腺腫にとどまるか，③消失するか，のいずれかをたどる．(2)腺腫を放置したときの1年後の癌化率は1.3％程度である．しかし，放置し続けると最終的には36％ほどの癌化率を持つ可能性もある．したがって，腺腫は内視鏡的ポリペクトミーの適応となる病変である．(3)表面型腺腫の一部は隆起型腺腫に発育進展する．(4)腺腫は発生すると定められた大きさまでに急速に発育して，その大きさにとどまる．年間増大率はせいぜい33％であった．(5)腺腫は異型度進展すると急速に発育する．(6)m癌は平均約1mm/月程度の発育をする．

　To survey the natural course of colorectal adenoma, 53 diminutive adenomas were followed prospectively and 13 adenomas were followed retrospectively. The three natural courses of adenoma were shown. The first was to mutate to carcinoma and grow rapidly. The second was to remain adenoma and stay the almost same size. The third was to disappear. To know the rate of each, course, the accumulation curves of adenoma and carcinoma were drawn. The object was 458 cases (male 391 female 67, the average age 55.2) and their 2,820 neoplastic tumors. They were examined with colonoscopy for more than four years. The colonoscopy was 2,818 times during the four years. At the each time of colonoscopy, all lesions were excised and histological study was performed. From those curves, the rate of mutation from adenoma to carcinoma for one year was calculated to be about 1.26%. The rate of disappearance for one year was more than 11.0% and less than 16.0%. If the adenoma is left as it is, the final risk of mutation to carcinoma was calculated to be about as large as 36%. Therefore adenoma should be excised with endoscopical polypectomy method. To know the fate of various kinds of adenoma, their accumulation curves were drawn about the same object from the point of atypism and shape. Some parts of flat adenoma were thought to grow up to be polypoid type of adenoma. Adenoma was thought to be born and grow rapidly up to the defined size and stay the same size. Some adenomas were thought to mutate to the adenoma with the higher grade of atypism and grow up to the larger defined size and stay that larger size. Some adenomas were thought to mutate to carcinoma. Carcinoma did not stop growing. The average speed of growing of mucosal carcinoma was estimated about 1 mm/month.