As with the other cancers, changes in a cell’s genetic material or mutations are the cause. In up to 10% of cases, these mutations may be inherited (hereditary colorectal cancer), in about 25% there is a familial association with no known causal mutation (familial colorectal cancer) and in the remaining 65% of cases the mutations occur throughout life (sporadic colorectal cancer). They can be caused by harmful substances, but can also occur accidentally during cell division. Normally, cells have repair systems to eliminate defects that originate in genes, but these mechanisms are more likely to fail as we age. In most patients, intestinal tumours originate in the glandular cells of the mucosa lining the inside of the intestine (adenocarcinomas). These cells begin to proliferate and generate polyps or clusters of non-cancerous (benign) cells, which slowly develop into malignant cancer cells. Although in most cases of colorectal cancer it is not possible to find a specific cause, we do know some of the risk factors that are associated with the development of colon cancer. Age over 50 years Inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease A diet high in fat and low in fibre Obesity Smoking Alcohol A family history of colon cancer is also a risk factor. The more members of the same family who have had colon cancer (especially first-degree relatives such as parents, siblings or children), the greater the likelihood of developing it.