Cancer is the uncontrolled growth and spread of abnormal cells in the body.
Usually the body's defenses destroy abnormal cells, but cancer occurs when those cells manage to overcome the defenses and grow out of control. Benign tumours do not spread, and can usually be completely removed. Malignant tumours may spread to other parts of the body through the blood vessels or lymph channels, creating more tumours. Often, it is these secondary tumours that are responsible for symptoms and death. One in three people will be diagnosed with cancer.