A leukaemia is a type of cancer of the white blood cells in the blood and bone marrow.

The word itself means 'white blood' and was first used by a German doctor in the 19th century. At that time, there was very little understanding about what made up blood and how it could become abnormal.

It had been known for a long time that if you took a sample of blood and left it to settle, it divided into several layers. There was a red layer of red cells at the bottom, a yellow liquid layer of plasma on top with a white/green layer of white cells in the middle.

In a patient with leukaemia, the massive increase in white cells in the blood meant that this layer was much larger and the blood itself looked different. It was much thicker, less red (because of anaemia) and more white/green (because of the white cells). Some early scientists described it as resembling pus mixed with blood!

As our knowledge has increased, we have been able to split this very general term into smaller more precise groups.

We are now able to stain blood cells and group them based on what they look like under the microscope. As a result we now know there a many different types of leukaemia. Special blood tests can add extra information and these help us to identify precisely which sort of leukaemia a person has by recognising the type of cell that has become cancerous.

We can also divide the leukaemias by their behaviour into some that behave very aggressively and acutely and others that behave more slowly and chronically.

This means that leukaemias are usually described by both their behaviour and the type of white cell that is affected. So, for example, chronic myeloid leukaemia is a slow growing cancer of myeloid type white blood cells.

Ask your specialist what type of leukaemia you have, and how it got its name. It is important to remember that the treatments and outlooks for each type of leukaemia will vary.