What is cancer?

Cancer is a disease of the body's cells, which are the body's basic building blocks. Our bodies constantly make new cells: to help us to grow, to replace worn-out cells, or to heal damaged cells after an injury.

Normally, cells grow and multiply in an orderly way, but sometimes something goes wrong with this process and cells grow in an uncontrolled way. This uncontrolled growth may develop into a lump called a tumour.

A tumour can be benign (not cancer) or malignant (cancer). A benign tumour does not spread outside its normal boundary to other parts of the body. However, if a benign tumour continues to grow at the original site, it can cause a problem by pressing on nearby organs.

The beginnings of cancer

How cancer spreads

A malignant tumour is made up of cancer cells. When it first develops, this malignant tumour may not have invaded nearby tissue. This is known as a cancer in-situ (or carcinoma in-situ). As the tumour grows, it invades surrounding tissue becoming invasive cancer. An invasive cancer that has not spread to other parts of the body is called primary cancer.

Sometimes cells move away from the original (primary) cancer and invade other organs and bones. 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.

Cancer is not just one disease but many diseases. There are more than 100 different types of cancer. Cancerous groups of cells or tumours are referred to as malignant tumours or a malignant disease. Most cancer forms a lump which is called a tumour, but some cancers, like leukaemia, which is a cancer of the blood or bone marrow do not.

Cancer can be classified into five broad categories:

• Carcinoma - cancer that begins in the skin or tissues that line or cover internal organs.
• Sarcoma - cancer that begins in the bone, cartilage, fat, muscle, blood vessels or other supportive tissues.
• Leukaemia - cancer that starts in blood forming tissue such as bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood.
• Lymphoma and Myeloma - cancers that begin in the cells of the immune system.
• Central nervous system - cancers that begin in the tissue of the brain and / or the spinal cord.

Some cancers may spread to another part of the body, the medical term for the spread of a cancer to another part of the body is called metastases.

Oncology

The branch of medicine that treats cancer is called oncology. Doctors working in the field of cancer may be called oncologists and will work with oncology nurses and other specialists. Most cancers can be treated through a range of treatments which aim to remove, reduce or slow down the cancer. Not all hospitals provide the full range of oncology services.

Benign tumours

Some solid lumps are called benign tumours, these are not cancer. Benign lumps or tumours do not grow in an unlimited aggressive manner like a cancer cell and do not invade surrounding cells or spread to other parts of the body.

More information

For more information about cancer call the Cancer Council Helpline  on 13 11 20.

The information available on this page should not be used as a substitute for advice from a properly qualified medical professional who can advise you about your own individual medical needs. It is not intended to constitute medical advice and is provided for general information purposes only. See our Disclaimer.