What is cancer?
Cancer is a disease of the body’s cells. Our bodies are always making new cells: so we can grow, to replace worn-out cells or to heal damaged cells after an injury. This process is controlled by certain genes. All cancers are caused by changes to these genes. Changes usually happen during our lifetime, although a small number of people inherit such a change from a parent.
Normally, cells grow and multiply in an orderly way. However, changed genes can cause them to behave abnormally. They may grow into a lump. These lumps can be benign (not cancerous) or malignant (cancerous).
Benign lumps do not spread to other parts of the body.
A malignant lump (more commonly called a malignant tumour) is made up of cancer cells. When it first develops, this malignant tumour is confined to its original site. If these cells are not treated they may spread into surrounding tissue and to other parts of the body.
The beginnings of cancer
How cancer spreads
When these cells reach a new site they may continue to grow and form another tumour at that site. This is called a secondary cancer or metastasis.
For a cancer to grow bigger than the head of a pin, it must grow its own blood vessels. This is called angiogenesis.