Hairy cell leukemia

Hairy cell leukemia (HCL) is an uncommon type of lymphocytic leukemia that starts in B cells, or B lymphocytes (a type of white blood cell). The World Health Organization (WHO) categorizes hairy cell leukemia as a mature B-cell neoplasm. It is called hairy cell leukemia because hair-like projections can be seen on the surface of the cancer cells when they are viewed under a microscope.

About 2% of all leukemias in adults are hairy cell leukemia. It is more common in men than in women. The average age at diagnosis is 50 years.

Hairy cell leukemia is usually chronic, but it often progresses. Most people will eventually need treatment.


When hairy cell leukemia first develops, the person may not have any symptoms or may have mild symptoms that slowly get worse over time. Someone with hairy cell leukemia usually has an enlarged spleen (called splenomegaly). Less often, the liver is enlarged (called hepatomegaly). The lymph nodes are usually not enlarged.

Other symptoms of hairy cell leukemia include:

  • fatigue
  • a general feeling of discomfort or illness (called malaise)
  • loss of appetite
  • weight loss
  • fever
  • shortness of breath
  • paleness
  • rapid heartbeat (called palpitations)
  • weakness
  • dizziness
  • vague feeling of fullness or pain in the upper-left part of the abdomen
  • easy bruising or bleeding


Diagnosing hairy cell leukemia usually begins with a visit to your family doctor or when a routine blood test suggests a problem with the blood. Your doctor will ask you about any symptoms you have and do a physical exam to check if your spleen or liver is enlarged. Based on this information, your doctor will order tests to check for hairy cell leukemia or other health problems.

Tests used to rule out or diagnose hairy cell leukemia include:

  • complete blood count (CBC) to measure the number and quality of white blood cells, red blood cells and platelets
  • ultrasound or CT scan of the abdomen to see if the spleen or liver is enlarged
  • bone marrow aspiration and biopsy to confirm whether or not you have leukemia and, if so, the type of leukemia

Find out more about these tests and procedures.


There is no standard staging system for hairy cell leukemia. Instead, hairy cell leukemias are divided into 3 groups:


Hairy cell leukemia is considered untreated when it is newly diagnosed and no treatment is needed. In untreated hairy cell leukemia:

  • There are hairy leukemia cells in the bone marrow and blood.
  • The number of red blood cells, white blood cells or platelets may be lower than normal.
  • The spleen may be enlarged.


Hairy cell leukemia is considered progressive when it has been treated with chemotherapy or the spleen has been removed, and 1 or both of the following apply:

  • There is a greater number of hairy cells in the bone marrow or blood.
  • The number of red blood cells, white blood cells or platelets is lower than normal.

Relapsed or refractory

Hairy cell leukemia is considered relapsed when it comes back after treatment. Hairy cell leukemia is considered refractory when it does not respond to treatment.


Treatment is usually given if hairy cell leukemia starts to progress. Signals that the disease is progressing include symptoms getting worse, low blood cell counts and frequent infections.

Your healthcare team will create a treatment plan just for you. You may be offered the following treatments for hairy cell leukemia. (For more detailed information on specific drugs, go to sources of drug information.)

Watchful waiting

You might not need treatment right away if you don’t have any symptoms or your symptoms are mild and your blood cell counts are not too low. Your healthcare team will watch you closely. Treatment is started if the following symptoms develop or get worse:

  • frequent infections
  • low blood cell counts that continue to stay low
  • discomfort from an enlarged spleen

Supportive therapy

Hairy cell leukemia and its treatments can cause certain problems, including infection, bleeding and low blood cell counts. If you develop these problems, you may be given:

  • antibiotics to prevent and treat infections
  • transfusions of red blood cells and platelets to raise low blood counts
  • growth factors such as filgrastim (Neupogen) and pegfilgrastim (Neulasta)

Growth factors may be used to stimulate the body to make white blood cells. They can shorten the length of time you have a low white blood cell count and so lower the risk of infection.


Chemotherapy uses anticancer, or cytotoxic, drugs to destroy cancer cells. It is usually a systemic therapy. This means that the drugs travel through the bloodstream to reach and destroy cancer cells all over the body. Chemotherapy drugs used to treat hairy cell leukemia include:

  • cladribine (Leustatin)
  • pentostatin (deoxycoformycin, Nipent)

Targeted therapy

Targeted therapy is sometimes used to treat hairy cell leukemia. It uses drugs to target specific molecules (such as proteins) on the surface of cancer cells. These molecules help send signals that tell cells to grow or divide. By targeting these molecules, the drugs stop the growth and spread of cancer cells while limiting harm to normal cells. Targeted therapy may also be called molecular targeted therapy.

Rituximab (Rituxan) is the most common targeted therapy drug used to treat progressive, relapsed or refractory hairy cell leukemia.

Biological therapy

Biological therapy is sometimes used to treat hairy cell leukemia. It uses natural or artificial substances to kill, control or change how cancer cells behave.

Interferon alfa (Intron A, Wellferon) is a type of biological therapy that is commonly used to treat progressive, relapsed or refractory hairy cell leukemia.


Most people with HCL will have surgery to remove the spleen (called splenectomy). Removing the spleen will partially or completely return blood cell counts to normal.

You may be offered splenectomy if you have:

  • pain from an enlarged spleen that cannot be controlled
  • relapsed or refractory hairy cell leukemia

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Follow-up after treatment is an important part of cancer care. Follow-up for hairy cell leukemia is often shared among the cancer specialists (oncologists) or blood specialists (hematologists) and your family doctor. Your healthcare team will work with you to decide on follow-up care to meet your needs.

Don’t wait until your next scheduled appointment to report any new symptoms and symptoms that don’t go away.

Expert review and references

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  • National Cancer Institute. Hairy Cell Leukemia Treatment (PDQ®) Health Professional Version. Bethesda, MD: National Cancer Institute; 2014.
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