Cancer Basics

In a healthy body, the cells in your body normally divide and grow to replace dying or dead cells. This process is controlled by the genes in the cell (your DNA). Sometimes, the genes change (mutate) and the cells start to divide and grow out of control. These cells are referred to as being cancerous or malignant.

Cancer is not one disease, but refers to more than 100 diseases in which genes have mutated and certain cells grow out of control. These cells can spread throughout your body. They can destroy normal body tissue and interfere with normal organ functioning.

Cancer and tumours are often linked. A mass of cancerous cells is commonly called a tumour. In some cases, tumours start in one part of the body and then spread to other locations, a process called metastasis. Not all tumours are cancerous and some do not spread. Not all cancers produce tumours. For example, leukemia is a cancer of the blood cells.

There are many possible causes of cancer. Some you may be able to change, such as stopping smoking. Others cannot be changed, such as your family history, gender or age. No one can predict who will get cancer. But some people may be at a higher risk than others. If you are in a "high-risk" group you may want to talk with your doctor about things you can do to reduce your risk.

You can read about the four main types of cancer in the next section.