Cancer is a disease of the cells. The body contains over two hundred different types of cell so there are also over two hundred different forms of cancer that occur if a particular cell type 'goes wrong'.

A normal cell grows and reproduces according to the strict instructions:
        • If it becomes damaged, it dies.
        • It reproduces a limited number of times before dying.
        • It responds to chemical messages from other cells which tell it what to do.
        • If it travels to the wrong place in the body, it dies.

Cancer occurs when a single cell divides (makes a copy of itself) but 'goes wrong' and produces an abnormal cell. If the abnormal cell continues to divide and does not die, it has become a cancer cell. It has the potential to spread throughout the body although it does not always do this.

There are two main types of cancer:
        • Solid cancers/tumours are when an abnormal cell divides rapidly and a lump forms.
        • Leukaemias and lymphomas are caused when the blood cells divide and multiply abnormally.

What is the difference between benign and malignant tumours?
A benign tumour is non-cancerous, which means they do not have the ability to spread to other parts of the body. They can cause a problem if they grow too large and press on surrounding parts of the body, interfering with the way they work.

A malignant  tumour is cancerous. These tumours can spread to other parts of the body. These are called 'metastases', where the original cancer has 'metastasised'. It is the ability to spread that is the difference between the cells in a benign and malignant tumour. Many doctors use the word ‘malignant’ to mean cancer.
Malignant tumours are classified according to how far they have spread in the body (their stage) and by the type of cancer cells they contain (their grade).