What is Cancer?
Your body is made up of different groups of specialised cells which are so small you can only see them with a microscope. All of your organs and tissues are made from cells which are continually reproducing to replace the old ones as they die through normal wear and tear. This process usually occurs in an organised manner. However, if this process gets out of control the cells may continue to divide, developing a lump, called a tumour.
A tumour can be either benign or malignant. In a benign tumour the cells do not spread to other parts of the body and so are not cancerous. A malignant tumour contains cancer cells that have the ability to spread beyond the original site, and can invade and destroy surrounding tissue if left untreated. These cells can also break away and spread to other organs in the body. When they develop in a new site this new tumour is called a 'secondary' or 'metastasis'.
Not all cancers form tumours though, such as cancers of the blood. These are called leukaemias and occur when cancer cells start to replace normal white cells which are used to fight infections. If our bodies cannot fight infections we become very ill.
If we get a normal virus our bodies recognise it as an invasion and will fight against it. However, the body does not recognise cancer cells as a potential problem and as such we have no mechanism to fight back with. Therefore cancer treatments have been developed with an intention to kill cancer cells.