Most polyps, with the exception of the inflammatory pseudopolyps, result from some form of genetic (DNA) mutation in one of the colon lining cells. Fortunately, several, probably at least five, mutations are needed in the same cell before cancer occurs and most benign polyps probably only have one gene mutated. DNA damage occurs surprisingly often. Even in a healthy adult's colon, about 10 per cent of the lining cells, on average, contain major abnormalities of the chromosomes (packages of DNA that contain many genes). Fortunately, almost all these cells seem to undergo a form of programmed death called apoptosis, and then fall off harmlessly into the bowel lumen (cavity). Adenomatous polyps, even those from individuals who do not have familial polyposis, commonly contain mutations that stop the gene working in both copies of the Adenomatous Polyposis Coli (APC) gene, the gene that is mutated in familial polyposis coli.