CLL and types of chronic leukaemia

Men and women discussing chronic lymphocytic leukaemia

This page tells you about the difference between chronic lymphocytic leukaemia (CLL) and other types of chronic leukaemia. There is information about

A quick guide to what's on this page
Acute or chronic leukaemia
The most common types of chronic leukaemia – CML and CLL
Prolymphocytic leukaemia and Richter's syndrome
Hairy cell leukaemia

Chronic or acute leukaemia

Leukaemias can be chronic or acute. Chronic leukaemias develop slowly and get worse 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. Acute leukaemias tend to develop quickly and get rapidly worse if they are not treated.

The two most common types of chronic leukaemia are chronic myeloid leukaemia (CML) and chronic lymphocytic leukaemia (CLL). If you are looking for information about chronic myeloid leukaemia, look in the CancerHelp UK section about chronic myeloid leukaemia (CML). There is also a section about a very rare type of CLL called hairy cell leukaemia.

Over time, CLL may change into another type of leukaemia called prolymphocytic leukaemia. This happens to about 10 out of every 100 people with CLL. Doctors call this change from one type of leukaemia to another transformation.

Rarely, advanced CLL can also change into a cancer of the lymphatic system (lymphoma) called Richter’s syndrome.

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Leukaemias are cancers of the white blood cells. Dividing leukaemias into acute and chronic types is one of the two main ways of grouping them. It describes how quickly or slowly they are likely to grow.

Chronic leukaemias develop slowly. The bone marrow makes too many abnormal white blood cells and they are almost fully developed. So they can still work, but not as well as they should do. Chronic leukaemia tends to get worse slowly.

Acute leukaemias tend to develop quickly and get rapidly worse if they are not treated. The bone marrow produces many immature white blood cells that cannot work properly.

This section of CancerHelp UK is about chronic lymphocytic leukaemia (CLL). The links below go to sections about the other main types of leukaemia

The two most common 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 (CGL). Myeloid is pronounced my-el-oyd and granulocytic is pronounced gran-you-low-sit-ik.

If you are looking for information about 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 about chronic myeloid leukaemia (CML).

In about 10 out of every 100 people (10%) the CLL changes over time into another type of leukaemia called prolymphocytic leukaemia. Doctors call this 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. About 5 out of every 100 people with CLL (5%) will develop Richter's syndrome.

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.