CLL and types of chronic leukaemia

• A quick guide to what's on this page
• Why leukaemias are called acute or chronic
• The two commonest types of chronic leukaemia - CML and CLL
• Prolymphocytic leukaemia and Richter's syndrome
• Large granular lymphocytic leukaemia
• Hairy cell leukaemia

This is one of the two main ways of grouping leukaemias, or cancers of the white blood cells. It describes how quickly the leukaemia is likely to develop and get worse. Chronic leukaemias develop slowly. In chronic leukaemia the cells are almost fully developed, but are not completely normal. They can still work, but not as well as they should do. Too many abnormal white blood cells are made. But they aren't made as quickly as in acute leukaemia. Chronic leukaemia tends to get worse slowly.

Acute leukaemias tend to develop quickly and get rapidly worse if they are not treated. This section of CancerHelp UK is about chronic myeloid leukaemia. There are other sections on acute myeloid leukaemia, acute lymphoblastic leukaemia and chronic lymphoblastic leukaemia.

The two commonest types of chronic leukaemia are

• Chronic myeloid leukaemia (CML)
• Chronic lymphocytic leukaemia (CLL)

The difference between them is the type of white blood cell that has become cancerous. In CLL the abnormal cells develop from the lymphoid blood stem cells. The cancerous white blood cells are B lymphocytes, also called B cells. (Lymphocytic in CLL is pronounced lim-fo-sit-ik.)

In CML, the abnormal cells develop from the myeloid blood stem cells. So the cancerous white blood cells are myelocytes. These cells are sometimes called granulocytes. So you may hear this type of leukaemia called chronic granulocytic leukaemia or CGL. (Myeloid is pronounced 'my-el-oyd' and granulocytic 'gran-you-low-sit-ik'.)

If you are looking for information on chronic myeloid leukaemia, this is not the right section of CancerHelp UK for you. You need to use this link to go to the section on chronic myeloid leukaemia (CML).

In about 1 in 10 people with CLL, over time it changes into another type of leukaemia called prolymphocytic leukaemia. Doctors call this change from one disease to another 'transformation'. Sometimes prolymphocytic leukaemia is diagnosed in people who have not had CLL.

Advanced CLL can sometimes develop into a cancer of the lymphatic system (a lymphoma). This is called Richter's syndrome. In about 1 in 20 people with CLL it will go on to develop into Richter's syndrome.

This is a rare condition that is similar to CLL. There are 2 different types of lymphocyte blood cells - B cells and T cells. The white blood cells affected in CLL are B cells. The white blood cells affected in LGLL are T cells. This rare leukaemia tends to be diagnosed in younger people than CLL and is more common in women than men.

Although they are all similar diseases in many ways, these different types of chronic leukaemia all behave differently from one another.

Hairy cell leukaemia is a type of chronic leukaemia that is rarer than CLL or CML. The leukaemia cells have outgrowths that look like tiny hairs on their surfaces. These can be seen under a microscope and give this type of leukaemia its name.