If cells in the bone marrow start to duplicate out of control it is called leukaemia. In all other parts of the body, the extra duplicating cells develop into solid lumps called tumours. Cancer can affect virtually every part of us.

Cancer is described as benign when a tumour is not growing aggressively and affecting the healthy cells or tissues around it. The term malignant is used if a tumour is growing quickly and affecting other tissues. Cells can break off from a malignant tumour and start to grow in another part of the body, this is known as a secondary tumour.

Different stages

There are over 200 different kinds of cancer. Each kind is a separate disease with its own characteristics but there are general terms used to describe how developed a cancer is. In many cancers there are four main stages:

• Stage one: The tumour is very small and has not spread outside the original site. There are usually no symptoms and the tumour cannot be felt. Stage one tumours are normally detected by chance or during a routine medical examination.
• Stage two: The tumour is still localised, but may be felt during examination or may show up on scans.
• Stage three: A tumour which has spread to tissues immediately alongside the original site.
• Stage four: A tumour which has spread more widely to other, often distant, organs such as the liver, lungs and the lymphatic system. This is known as secondary cancer, or metastatic disease.

Screening is an important method of detecting cancer at an early stage. This means that it is more likely to be curable. As you get older screening and self examination become more and more important.