1999 年 18 巻 2 号 p. 81-92
As the cause of one disease becomes clear and specific therapies for it are established, other diseases formerly of lesser importance become serious problems. Ulcerative colitis and Crohn's disease, which were unfamiliar diseases in Japan about 20 years ago, are on the increase. The cause remains unclear, but the tendency seems to be closely related to changes in Japanese lifestyle, especially to changes in diet, which has become more similar to the Euro-American diet. Part 1 of this paper outlines the recent development of colonic inflammatory diseases in Japan as seen by the pathologist. The endoscope has enabled remarkable clinical progress, and colonoscopic examinations are performed readily in most patients who complain of intestinal problems. There are many opportunities to detect polyps of the colon, and such polyps rank with inflammatory bowel diseases. The adenoma-carcinoma sequence theory was proposed by Morson in 1968, but most adenomas do not generate cancer over the long term, and the wide utilization of polypectomy has not decreased the colon cancer rate. There is some doubt as to whether all colon cancers develop from adenoma. In recent years, practitioners have discovered very small elevated, flat or depressed colon carcinomas that have no polyp (adenoma) component. There are known as de novo cancers. However, neither the adenoma-carcinoma sequence nor de novo cancer give a complete account for the carcinogenesis of colon cancer yet. Part 2 of this paper explores the pathohistological relation between adenoma and carcinoma.