Hereditary Non-polyposis Colorectal Carcinoma (HNPCC)

Overview

Lynch´s Syndrome Lynch´s syndrome (hereditary non-polyposis colorectal carcinoma - HNPCC) is an autosomal dominant predisposition in particular for colorectal carcinoma but also for carcinomas at other sites. The syndrome differs clinically and genetically from familial adenomatous polyposes of the colon. It is characterised in particular by young age at the time of the occurrence of the tumour, by a strikingly frequent localisation in the proximal colon, a more frequent incidence of synchronous and metachronous tumours. Extraintestinal carcinomas are mostly endometri- al, but also ovarian, gastric or at other sites. The incidence of the syndrome is so far not reliably known; according to estimates the syndrome participates in 5-15% of all colorectal carcinomas. Early detection of the syndrome which is possible so far in clinical practice only on the basis of a careful family-history can contribute considerably towards early diagnosis and prevention of colorectal carcinoma assuming periodic coloscopic monitoring of suspect cases. The authors achieved their best results with detection of the syndrome in the completely asymptomatic stage. A molecular biological basis was revealed only recently. An important step towards this was the discovery of microsatellite instability in HNPCC tumours, which results from gene mutations which repair the replication errors of DNA and thus maintain the stability of the genome. The identification of four HNPCC genes opens a new perspective of genetic testing with accurate identification of subjects with the highest risk, with a possibility of tumour development prevention. The appropriate methods are being introduced in our country and their clinical application may be foreseen in the near future.

Key words:
colorectal carcinoma - coloscopy - mutation.