Cancer describes any malignant tumour and arises from the abnormal and uncontrolled division of cells that then invade and destroy the surrounding tissues.
The cancer cells often spread (metastasis), setting up secondary tumours at sites distant from the original tumour. Treatment of cancer depends on the type of tumour, the site of the primary tumour and the extent of the spread.
Who is at risk? There are probably many risk factors that can increase a person's chance of getting cancer, some of which are known, such as cigarette smoking, an unhealthy diet or sun exposure.
However, having one or more risk factors does not necessarily mean that a person will get cancer. Some people with one or more risk factors never develop the disease, while other people who do develop cancer have no apparent risk factors. Even when a person who has a risk factor is diagnosed with cancer, there is no way to prove that the risk factor actually caused the cancer.
Reducing the risk The risk of developing most types of cancer can be reduced by changes in a person's lifestyle, for example, by quitting smoking, eating a healthy diet and regular exercise. Research shows that about one-third of all cancer deaths are related to dietary factors and lack of physical activity in adulthood.