any cancer that affects the last section of the digestive system. This usually means the colon (large bowel) or rectum (back passage).
Colon cancer is caused by the abnormal growth of cells in the lining of the bowel. Usually small lumps called polyps begin to form. Commonly these lumps are referred to as tumours.
The growth of polyps can be harmless, these are known as benign tumours. However, these polyps can also be caused by the growth of cancer cells. These are called malignant tumours.
If left untreated, these cancerous growths can spread to other parts of the body.