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    Hairy Cell Leukemia

    Hairy cell leukemia is a slowly progressing cancer of the blood and bone marrow. It is a rare type of chronic leukemia that mostly affects middle-aged adults. It rarely affects children. Most people with hairy cell leukemia have normal life expectancy with treatment.

    What is hairy cell leukemia?

    Hairy cell leukemia (HCL) is a rare cancer in which the bone marrow (soft inner part of bones) makes too many B-cells. B-cells are white blood cells. White blood cells fight off infections.

    HCL affects B-cells once they have matured. These mature B-cells develop changes in their DNA (genetic material), causing them to function abnormally. They look hairy when viewed under a microscope, giving the condition its name.

    These cancerous cells build up in the bone marrow and eventually spill over into the blood. This allows the cancer to spread to other areas of the body.

    Hairy cell leukemia facts and stats

    • Hairy cell leukemia accounts for 2% of all adult leukemias.
    • One thousand people are newly diagnosed with HCL yearly in the United States.
    • Median age at diagnosis is 55 years.
    • 85-90% of people with HCL achieve complete remission (elimination of cancer symptoms).
    • Around 50% of people in HCL remission survive without relapse (cancer return) for ten years.

    Causes and risk factors of hairy cell leukemia

    Most people (≥95%) with HCL have a mutation (change) in the V600E BRAF gene. This change allows B-cells to divide rapidly, survive, and become cancerous without control.

    HCL is not passed down from your parents. Instead, these mutations occur during a person’s lifetime.

    Risk factors for HCL include:

    • Agent Orange exposure
    • Ashkenazi Jewish ancestry
    • Family history of HCL (This does not mean that you inherit HCL from your parents. Instead, the risk of developing the same type of genetic mutation after birth slightly increases.)
    • Large-animal farming
    • Middle-aged men (four times as likely than in women)
    • Pesticide/chemical exposures
    • White ethnicity

    Signs and symptoms of hairy cell leukemia

    Signs and symptoms of hairy cell leukemia happen slowly over time and may include:

    • Easy bruising
    • Fatigue
    • Pain or feeling of fullness below the rib cage
    • Recurrent fevers/frequent infections
    • Shortness of breath during everyday activities
    • Swelling of lymph nodes
    • Unexplained weight loss

    Diagnosing hairy cell leukemia

    Your doctor performs a physical exam and asks about your medical history to diagnose HCL. They might discover that your spleen is larger than it should be. Enlargement of the spleen occurs in more than 90% of patients with HCL.

    Tests may include:

    • Blood tests: These tests measure the number of platelets, white blood cells, and red blood cells in your blood sample. Blood tests help analyze liver and kidney function and find signs of inflammation and infection.
    • Peripheral blood smear: Laboratory specialists place a blood sample on a slide to look at the blood cells under a microscope. “Hairy” white blood cells may appear once they spill over from the bone marrow to the blood.
    • Bone marrow aspiration or biopsy: Your doctor uses a thin, hollow needle to remove small samples of bone marrow or bone tissue for analysis. This test identifies abnormal, hairy B-cells in the bone marrow. This test is the most common and reliable method for HCL diagnosis.
    • Imaging: Imaging locates affected lymph nodes and tumors. It also allows doctors to measure the size of enlarged organs, such as the spleen or liver. Imaging studies may include:
      • Computed tomography (CT) scans
      • Magnetic resonance imaging (MRI) scans
      • Ultrasounds (US)
    • Genetic testing: This test detects the mutation in the V600E BRAF gene, confirming the HCL diagnosis. Results guide your doctor’s treatment recommendation.

    Treatments for hairy cell leukemia

    Treatment depends on your current symptoms, how fast the HCL progresses, and your response to treatment.

    Treatment options for HCL include:

    • Watch and wait: Your doctor may recommend monitoring your condition without immediate treatment. HCL progresses very slowly, so the doctor starts treatment when symptoms appear. This method delays harmful side effects of treatment.
    • Chemotherapy: Chemotherapy drugs kill cancer cells. You receive this treatment either in pill form or as injections into a vein, muscle, or underneath the skin.
    • Immunotherapy: Immunotherapy is a type of treatment that enhances your immune system’s ability to fight the cancer. Immunotherapy drugs called monoclonal antibodies treat HCL recurrence (return of the cancer).
    • Targeted therapies: New drugs called shut down or slow specific pathways involved in HCL. Other targeted therapies have also been developed to treat HCL.
    • Splenectomy: Although rare, doctors remove the spleen if it is too large or causes discomfort. Some patients may achieve long-term remission after this surgery.
    • Stem cell transplant (bone marrow transplant): Your doctor may suggest a bone marrow transplant. Healthy stem cells (blood-forming cells in the bone marrow) replace unhealthy stem cells. Healthy stem cells most often come from a donor but may also come from your own healthy cells.
    • Clinical trials: Researchers develop and test new drugs through clinical trials at specific medical sites. Eligible patients may gain access to these promising treatments by participating in these trials. These treatments usually are not widely available.
    • Supportive therapies: These therapies may replace or support intensive treatments, such as chemotherapy. They can provide relief from cancer symptoms or treatment-related side effects. Supportive therapies may include:
      • Antibiotics to treat recurrent infections
      • Blood transfusions to treat low platelet and red blood cell levels
      • Counseling
      • Diet
      • Meditation and relaxation exercises
      • Pain management
      • Physical exercise

    Helpful resources

    Support can make a significant difference when you face a cancer diagnosis. You can connect with others who understand these challenges through our peer support programs. We offer an online support community and a mentoring program. We also have a directory of resources to help patients, families, and caregivers.

    Clinical Trials Hub: A resource for leukemia patients and caregivers

    Do you have questions about clinical trials? On our new Clinical Trials Hub learn how clinical trials are developed or if they are right for you. You can also use the new Search Tool to see if there is a current leukemia-focused trial you would qualify for.

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