This view is supported by the fact that while rare genetic variants with high penetrance do confer a predisposition for inherited forms of CRC, such as the APC gene mutation in familial adenomatous polyposis (FAP) and the mismatch repair (MMR) gene mutation in Lynch syndrome, they account for only about 5% of CRC cases2. The gene discussed is APC; the disease is Familial adenomatous polyposis.