What is cancer?

Cancer is a disease of the cells in the body. Normal body cells grow and divide and know when to stop growing. Over time they also die. Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new abnormal cells. Cancer cells can also invade (grow into) other organs and tissues, something that normal cells cannot do.

Cancer cells usually group or clump together to form tumours. Some cancers like leukaemia rarely form tumours. Instead, these cancer cells involve the blood and circulate through other tissues where they grow. Different types of cancer can behave very differently. For instance, breast cancer and skin cancer are very different diseases. They grow at different rates and respond to different treatments. This is why people with cancer need treatment that is specifically aimed at their type of cancer.

What causes cancer?

A cancer cell is one which grows out of control and invades other tissues. Cancer cells usually have changes to their DNA (deoxyribonucleic acid). DNA is in every cell and directs its actions. In a normal cell, when DNA is damaged the cell either repairs the damage or dies. In a cancer cell, the damaged DNA is not repaired and the cell doesn’t die. Instead the cell goes on to make new cells that the body does not need. The new cells have the same damaged DNA as the first cell. People can inherit abnormal or faulty DNA from their parents, but most DNA damage is caused by mistakes that happen while a normal cell is reproducing or by something in the environment. Sometimes DNA damage can be caused by something obvious like cigarette smoking, asbestos exposure or sun exposure, but it’s rare to know exactly what has caused any one person’s cancer.

How does cancer spread?

Sometimes cancer cells break away from the original tumour and travel to other areas of the body through the bloodstream or lymph vessels, where they keep growing and can go on to form new tumours. The spread of a tumour to a new place in the body is called a metastasis. No matter where a cancer may spread, it is always named on the place where it first started (the primary site). For instance, prostate cancer that has spread to the bones is called metastatic prostate cancer, not bone cancer.

Cancer Types

Click the arrow to access more information about a particular type of cancer.