What is cancer?
Cancer Institute NSW
Published 18 October 2018
The human body contains billions of cells. As old cells die, other cells divide to make new cells. This process happens in the body millions of times a day.
Cancers start when some cells in the body become abnormal, multiply out of control, and take over from normal cells in the area.
These cells don't behave the same way as normal cells: they can grow and divide faster, or live for longer.
As time passes, more and more abnormal cells are made and they start to outnumber normal cells in the area. They multiply out of control and form a cancer.
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Cancer treatments are designed to stop or slow down this process. They work by removing the abnormal cells, killing them, or stopping them from growing and dividing.
Cancer is not really a single disease – there are more than 200 types of cancers.
Differences can include:
- They start in different types of cells and different parts of the body.
- They affect people of different ages.
- Some are common and others are rare.
- Some grow quickly and others grow slowly.
- Some cause a lot of symptoms and others don’t cause many.
- Some form tumours (lumps) and others don’t.
This is why the experience of having cancer is not the same for everyone.
People with different cancers have different symptoms, they need different tests and treatments, and their chances of recovery after treatment are also different.
What are the different cancer types?
Cancers are generally named after the part of the body where they start or the type of tissue they start in, for example:
Each type of cancer can be divided further, usually based on the kind of cell they start in, for example:
- Skin cancers can be basal cell carcinomas, squamous cell carcinomas or melanomas (which start in cells called melanocytes).
- Lung cancers can be small lung cell cancers or non-small cell lung cancers.
Cancers can also be described by other characteristics, like whether they have certain receptors on their cells.
What are the different cancer groups?
The different types of cancers belong to two main groups:
- solid tumours
- blood cancers (also called haematological cancers).
Solid tumours
Solid tumours include many common cancers like breast cancer, bowel cancer and lung cancer.
A tumour is a lump or swelling, but not all tumours are cancers:
- Benign tumours are not cancers—they can cause problems if they press on nearby tissues or organs, but they don’t spread to other parts of the body.
- Malignant tumours are cancers—they can spread into nearby tissues or to other parts of the body.
Surgery is often used to remove solid tumours, however other treatments like chemotherapy or radiotherapy may be needed if the tumour has spread.
Blood (haematological) cancers
Blood cancers affect the blood, bone marrow or lymphatic system. They include leukaemias, lymphomas and myelomas.
Characteristics of blood cancers include:
- They don’t form solid tumours in the place where they start.
- Most of them start in the bone marrow where blood cells are formed.
- Their cells multiply within the blood or lymphatic system and crowd out the normal cells.
- They stop the normal blood cells from performing their normal functions, like preventing infection or stopping bleeding.
Most blood cancers are treated with chemotherapy and/or radiotherapy to help to bring the cancer under control.
Visit Patient Information to learn about cancer diagnosis, treatment and possible side effects. You will find practical advice about dealing with cancer and finding support.
We also recommend links to more detailed information.