What is small lymphocytic lymphoma (SLL)?

Small lymphocytic lymphoma (SLL) is a type of blood cancer. It is the same as chronic lymphocytic leukaemia (CLL).

SLL and CLL develop when B-cells become abnormal (cancerous). B-cells are white blood cells that normally help fight infection. They are sometimes called B-lymphocytes. Although they have different names, they develop from the same type of B-cell.

Previously, when the abnormal B-cells were mostly in the lymph nodes and spleen, the type of blood cancer was called SLL. When the abnormal B-cells were mostly in the blood and bone marrow, it was called CLL. Most people have abnormal cells in the lymph nodes, spleen, blood and bone marrow. This is why SLL and CLL now considered to be the same condition.

It is more common as people get older. It usually develops slowly. You may not need treatment straightaway.

Symptoms, diagnosis and treatment

To find out more, see our information on chronic lymphocytic leukaemia. This explains: 

  • symptoms
  • causes and risk factors
  • diagnosis
  • stages
  • treatment. 

Getting support

Everyone has their own way of dealing with illness and the different emotions they experience. You may find it helpful to talk things over with family and friends or your doctor or nurse.

Macmillan is also here to support you. If you would like to talk, you can:

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Anne Parker, Consultant Haematologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Reviewed: 01 March 2021
Reviewed: 01/03/2021
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Next review: 01 March 2024
Next review: 01/03/2024