What is cancer?

Cancer is a disease of the body's cells. The body is constantly making new cells to replace worn-out ones, to grow, or to heal itself after an injury. Normally cells grow and reproduce themselves in an orderly way. Sometimes, cells can reproduce themselves in an uncontrolled way, which can lead to cancer.

In many cases we don't know why this happens, but we do know that a number of lifestyle risk factors can cause cells to change, such as smoking, drinking alcohol, UV radiation, being physically inactive or inheriting a faulty gene. These abnormal cells may grow into a lump called a tumour.

Tumours can be benign (not a cancer) or malignant (a cancer). Benign tumours do not spread to other parts of the body. A malignant tumour is made up of cancer cells. These cells can spread beyond the area where the cancer first developed. If untreated, the cancer cells may invade and destroy surrounding tissues.

Sometimes cells break away from the original (primary) cancer and may be carried to other parts of the body. When these cells reach a new part of the body they may continue to grow and form another tumour at that site. This is called a secondary cancer or metastasis.

It is important to understand that cancer is not a single disease with a single type of treatment. There are more than 200 different kinds of cancer, each with its own name and treatment.

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