Cancer is a disease of the cells, the body’s basic building blocks. Cancer occurs when abnormal cells grow in an uncontrolled way. The abnormal cells damage or invade the surrounding tissues, or spread to other parts of the body, causing further damage. Tumours can be benign (not cancer) or malignant (cancer).

Benign tumours do not spread outside their normal boundary to other parts of the body. Some benign tumours can be pre-cancerous and may progress to cancer if left untreated. Other benign tumours do not develop into cancer.

A malignant tumour is made up of cancer cells. When it first develops, a tumour is often confined to its original site. For example, in the liver. If the tumour is not treated, it may spread into surrounding tissues and become invasive.