A cancer for every type of cell in our bodies.
The uncontrolled growth causes a tumour to form which, if not treated, can cause problems by invading normal tissues nearby or by causing pressure on other body structures.
There are more than 200 different types of cancer because there are over 200 different types of body cells.
Unlike normal body cells, cancer cells do not stop reproducing after they have doubled 50 or 60 times.
Cancer cells may be able to stop themselves self-destructing, or they may self-destruct more slowly than they reproduce, so that their numbers continue to increase - scientists describe cancer cells as being immortal.
Eventually a tumour is formed that is made up of billions of copies of the original cancerous cell.
Cancer cells also do not obey signals - something in the cancer cells overrides the normal signalling system.
This may be because the genes that tell the cell to reproduce keep on firing, or because the genes that normally tell the cell to stop reproducing have been damaged or lost.
This allows cancer cells to keep on doubling up regardless of the damage caused to the part of the body where it is growing.
Cancer cells can lose the molecules on their surface that keep normal cells in the right place, enabling them to become detached from their neighbours.
This partly explains how cancer cells spread to other parts of the body.
Another characteristic of cancer cells, which helps them to multiply quickly is the fact that they do not become specialised.
Unlike normal cells, cancer cells do not carry on maturing once they have been made.
The cells in a cancer can actually become less mature over time - it is thought that multiple reproduction results in more of the genetic information in the cell becoming lost, making the cells more primitive but able to reproduce quickly and haphazardly.
Cancer starts with one cell, but it can take years before a detectable lump is formed.
There is no one cause of cancer, and different forms of the disease my be triggered by different things - such as the relationship between lung cancer and smoking, and between skin cancer and the sun.
In addition to known carcinogens, cancer may be linked to a person's genetic make-up, age, problems with the immune system, diet, viruses, or even the daily environment. Gender divide: For men the most common forms of cancer are:
Prostate cancer - 2,288 cases
Colorectal cancer - 1,140 cases
Lung cancer - 1,312 cases
For women the most common forms of cancer are:
Breast cancer - 2,314 cases
Lung cancer - 936 cases
Colorectal cancer - 919 cases
[source: Welsh Cancer Intelligence and Surveillance Unit] (number of cases in 2004)
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|Publication:||Western Mail (Cardiff, Wales)|
|Date:||Jun 26, 2006|
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