[Hereditary nonpolyposis colorectal carcinoma: state of the art].

Familial clustering is found in 20-25% of all cases with colorectal cancer (CRC), 4-5% revealing autosomal dominant inheritance. Hereditary CRC develops from adenomatous, hyperplastic hamartomatous juvenile lesions. Hereditory nonpolyposis colorectal cancer includes two genetically different tumor entities, those with and without microsatellite instability in the corresponding tumors. Those with such instability and with germ-line mutation in DNA mismatch repair genes (Lynch syndrome) have additional neoplasms, an earlier age at onset and a higher risk for syn- and metachronous cancers.