Chronic lymphocytic leukemia (CLL)

Alternative Names

CLL; Leukemia – chronic lymphocytic (CLL)

Definition of Chronic lymphocytic leukemia (CLL)

Chronic lymphocytic leukemia is cancer of a type of white blood cells called lymphocytes.

Causes, incidence, and risk factors

Chronic lymphocytic leukemia (CLL) causes a slow increase in the number of white blood cells called B lymphocytes, or B cells, in the bone marrow. The cancerous cells spread from the blood marrow to the blood, and can also affect the lymph nodes or other organs such as the liver and spleen. CLL eventually causes the bone marrow to fail, resulting in low blood counts, and weakens the immune system.


Symptoms usually develop slowly over time. Many cases of CLL are detected by blood tests done in people for other reasons or who do not have any symptoms.

Signs and tests

Patients with CLL usually have a higher-than-normal .


For most patients with early stage CLL, no treatment is started. However, these people must be closely watched by their doctor.

Expectations (prognosis)

The outlook depends on the stage and behavior of the disease. Half of patients diagnosed in the earliest stages of the disease live more than 12 years. Some people may not require any treatment at all, while others may have faster spreading disease that requires aggressive therapy with multiple chemotherapy agents.


David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 3/2/2010

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Auer rods
Chronic lymphocytic leukemia - microscopic view

ADAM Medical Encyclopedia

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