The hereditary form of colorectal cancer (Lynch syndrome, cancer family syndrome "nonpolyposis hereditary colorectal cancer"), which is different from familial adenomatous polyposis, represents probably 5-8% of the development of this malignancy. The main characteristics of the syndrome include an autosomal dominant hereditary type, frequent familial occurrence of colorectal cancer (either solely at this site--Lynch variant I--or in combination with other, particularly gynecological sites of cancer-Lynch variant II), younger age at the time of diagnosis, more frequent localization in the right colon and more frequent occurrence of synchronic and metachronic cancer. During the years 1982-1992, we found 339 asymptomatic members of families meeting the criteria of the syndrome. After initial colonoscopy these individuals entered a long-term surveillance system with repeated colonoscopies; intervals between them where organized according to the individual degree of risk and to at the initial finding. Results of initial colonoscopy showed colorectal cancer in 16.2% and adenomas in 32.1% of the whole group. The right colon was affected in 74.5% of the cancers and in 64% of the adenomas; the mean age of the probands with these findings was 46.4% years. The Lynch variant I was found in 34%, the variant II in 66%. Cancer in relatives of the variant II was mostly in the colorectal, followed by the gynecological region. The highest number of cancers detected on initial colonoscopy was found in probands with the highest degree of genetic risk-with 3 or more than 3 direct relatives. On repeated colonoscopies a new cancer was found in 7 further probands. All the cancers were well resectable, mostly DUKES A and B.(ABSTRACT TRUNCATED AT 250 WORDS)

4 interní klinika 1 lékarské fakulty Univerzity Karlovy Praha