Colorectal polyposis and inherited colorectal cancer syndromes.

The majority of colorectal cancer (CRC) cases are sporadic, with hereditary factors contributing to approximately 35% of CRC cases. Less than 5% of CRC is associated with a known genetic syndrome. Although adenomatous polyposis syndromes, hamartomatous polyposis syndromes, and those previously classified as non-polyposis CRC syndromes are quite rare, it is important for clinicians to know the characteristics of each syndrome and to understand the differences in cancer risks between the different conditions. This information is very important when treatment and surveillance plans are formulated for each individual patient.