What is bowel cancer?

Cancer cells are abnormal cells that have developed as a result of errors in the way normal cells in the body have reproduced, so that they become aggressive and start to spread to the surrounding tissues and even to other parts of the body.  Bowel cancer, also known as colorectal cancer or colon cancer,  is any cancer that affects the colon (large bowel) and rectum (back passage). It usually grows very slowly over a period of up to 10 years, before it starts to spread and affect other parts of the body. View a diagram of your digestive system to help you to understand more about the bowel.

Most bowel cancers start as benign innocent growths – called polyps – on the wall of the bowel. Polyps are like small spots or cherries on stalks and most do not produce symptoms. Polyps are common as we get older and most polyps are not pre-cancerous. One type of polyp called an adenoma can, however, become cancerous (malignant). If left undetected the cancer cells will multiply to form a tumour in the bowel, causing pain, bleeding and other symptoms. If untreated, the tumour can grow into the wall of the bowel or back passage. Once cancer cells are in the wall, they can travel into the bloodstream or lymph nodes; from here the cancer cells can travel to other parts of the body. For bowel cancer, the most common places for bowel cancer cells to spread to are the liver and the lungs. The process of spread is called metastasis.

Anal cancer is also another very rare form of bowel cancer which is linked very strongly to the HPV virus (Human Papillioma Virus) that also causes cervical cancer in women, and much less commonly to melanomas (a form of skin cancer) – both of which can be treated very successfully when diagnosed at an early stage. Please see our "Anal Cancer" factsheet for more information.
 

The earlier bowel cancer is caught, the easier it is to treat.

This is why it is so important to:

1. Know the symptoms of bowel cancer
2. Understand the causes of bowel cancer
3. Act if you develop symptoms of bowel cancer
4. Take part in the NHS bowel cancer screening programme when  you are invited to participate