Chronic lymphocytic leukaemia (CLL)

What is chronic lymphocytic leukaemia (CLL)?

CLL is a type of leukaemia (cancer of the blood). It is usually a slow-growing cancer of lymphocyte white blood cells.

CLL stops the white blood cells working properly to fight infection.

CLL also means that the lymphocytes don’t die off naturally at the end of their life span. The cells may build up in your lymph nodes and spleen, causing them to become swollen. They can also build up in your bone marrow, meaning there is not enough space for normal blood cells to develop. This causes problems with fighting infection, carrying oxygen and bleeding.

Many people with slow-growing CLL can live a normal life. Other people experience symptoms that affect their quality of life at different stages of their disease and treatment.

Small lymphocytic lymphoma (SLL)

 CLL and SLL both affect lymphocytes. They are different forms of the same disease. The difference between them is where the cancer is mainly found: 

• CLL: Most of the cancer cells are in the blood and the bone marrow. The lymph nodes and spleen may be affected too.
• SLL: Most of the cancer cells are in the lymph nodes.

If you have SLL and need more specific information, you can call our Support Line on 1800 200 700.

Medical content updated from our Understanding Chronic Lymphocytic Leukaemia booklet (2023). Reviewed by Dr Johnny McHugh, Consultant Haematologist, Sinead Lawlor, Clinical Nurse Manager, Liz O'Connell, Haematology Nurse Coordinator and Anna Drynan Gale, Daffodil Centre Nurse.