[Colorectal carcinogenesis. 1. Hereditary predisposition and colorectal cancer].

Tumors arising sporadically represent 70-80% of colorectal cancer (CRC). The two best defined forms of inherited CRC-familial multiple polyposis (FMP) and Hereditary Non-Polyposis Colon Cancer (HNPCC) account respectively for<1% and 2-3% of CRC. These rare genetic syndromes (FMP, HNPCC, Peutz-Jeghers Syndrome) are caused by major predisposing gene mutations (APC gene, MMR gene, BMPR1A. SMAD4,...) and local environmental factors play only a minor role. In the sporadic forms of CRC, 25% have significant genetic predisposition probably related to alleles with weak penetration (APC*I1307K, TGFbR1*6Ala...) and are more strongly affected by environmental factors.