Hairy cell leukemia is a cancer of the blood and bone marrow. This rare type of leukemia gets worse slowly or does not get worse at all. The disease is called hairy cell leukemia because the leukemia cells look "hairy" when viewed under a microscope.
Anatomy of the bone. The bone is made up of compact bone, spongy bone, and bone marrow. Compact bone makes up the outer layer of the bone. Spongy bone is found mostly at the ends of bones and contains red marrow. Bone marrow is found in the center of most bones and has many blood vessels. There are two types of bone marrow: red and yellow. Red marrow contains blood stem cells that can become red blood cells, white blood cells, or platelets. Yellow marrow is made mostly of fat.
Normally, the bone marrow makes blood stem cells (immature cells) that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell.
A myeloid stem cell becomes one of three types of mature blood cells:
A lymphoid stem cell becomes a lymphoblast cell and then into one of three types of lymphocytes (white blood cells):
Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.
In hairy cell leukemia, too many blood stem cells become lymphocytes. These lymphocytes are abnormal and do not become healthy white blood cells. They are also called leukemia cells. The leukemia cells can build up in the blood and bone marrow so there is less room for healthy white blood cells, red blood cells, and platelets. This may cause infection, anemia, and easy bleeding. Some of the leukemia cells may collect in the spleen and cause it to swell.
This summary is about hairy cell leukemia. See the following PDQ summaries for information about other types of leukemia:
Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn’t mean that you will not get cancer. Talk with your doctor if you think you may be at risk. The cause of hairy cell leukemia is unknown. It occurs more often in older men.Signs and symptoms of hairy cell leukemia include infections, tiredness, and pain below the ribs.
These and other signs and symptoms may be caused by hairy cell leukemia or by other conditions. Check with your doctor if you have any of the following:
The following tests and procedures may be used:
Complete blood count (CBC). Blood is collected by inserting a needle into a vein and allowing the blood to flow into a tube. The blood sample is sent to the laboratory and the red blood cells, white blood cells, and platelets are counted. The CBC is used to test for, diagnose, and monitor many different conditions.
Bone marrow aspiration and biopsy. After a small area of skin is numbed, a bone marrow needle is inserted into the patient’s hip bone. Samples of blood, bone, and bone marrow are removed for examination under a microscope.
The treatment options may depend on the following:
The prognosis (chance of recovery) depends on the following:
Treatment often results in a long-lasting remission (a period during which some or all of the signs and symptoms of the leukemia are gone). If the leukemia returns after it has been in remission, retreatment often causes another remission.
Staging is the process used to find out how far the cancer has spread. Groups are used in place of stages for hairy cell leukemia. The disease is grouped as untreated, progressive, or refractory.
Untreated hairy cell leukemia
The hairy cell leukemia is newly diagnosed and has not been treated except to relieve signs or symptoms such as weight loss and infections. In untreated hairy cell leukemia, some or all of the following conditions occur:
Progressive hairy cell leukemia
In progressive hairy cell leukemia, the leukemia has been treated with either chemotherapy or splenectomy (removal of the spleen) and one or both of the following conditions occur:
Relapsed hairy cell leukemia has come back after treatment. Refractory hairy cell leukemia has not responded to treatment.
Different types of treatment are available for patients with hairy cell leukemia. Some treatments are standard (the currently used treatment), and some are being tested in clinical trials. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment. Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.Five types of standard treatment are used:Watchful waiting
Watchful waiting is closely monitoring a patient's condition, without giving any treatment until signs or symptoms appear or change.Chemotherapy
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the cerebrospinal fluid, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). The way the chemotherapy is given depends on the type and stage of the cancer being treated. Cladribine and pentostatin are anticancer drugs commonly used to treat hairy cell leukemia. These drugs may increase the risk of other types of cancer, especially Hodgkin lymphoma and non-Hodgkin lymphoma. Long-term follow up for second cancers is very important.Biologic therapy
Biologic therapy is a cancer treatment that uses the patient’s immune system to fight cancer. Substances made by the body or made in a laboratory are used to boost, direct, or restore the body’s natural defenses against cancer. This type of cancer treatment is also called biotherapy or immunotherapy. Interferon alfa is a biologic agent commonly used to treat hairy cell leukemia.
See Drugs Approved for Hairy Cell Leukemia for more information.Surgery
Splenectomy is a surgical procedure to remove the spleen.Targeted therapy
Targeted therapy is a treatment that uses drugs or other substances to identify and attack specific cancer cells without harming normal cells. Monoclonal antibody therapy is a type of targeted therapy used to treat hairy cell leukemia.
Monoclonal antibody therapy uses antibodies made in the laboratory from a single type of immune system cell. These antibodies can identify substances on cancer cells or normal substances that may help cancer cells grow. The antibodies attach to the substances and kill the cancer cells, block their growth, or keep them from spreading. Monoclonal antibodies are given by infusion. They may be used alone or to carry drugs, toxins, or radioactive material directly to cancer cells.
A monoclonal antibody called rituximab may be used for certain patients with hairy cell leukemia.
Other types of targeted therapies are being studied.New types of treatment are being tested in clinical trials.
Information about clinical trials is available from the NCI website.Patients may want to think about taking part in a clinical trial.
For some patients, taking part in a clinical trial may be the best treatment choice. Clinical trials are part of the cancer research process. Clinical trials are done to find out if new cancer treatments are safe and effective or better than the standard treatment.
Many of today's standard treatments for cancer are based on earlier clinical trials. Patients who take part in a clinical trial may receive the standard treatment or be among the first to receive a new treatment.
Patients who take part in clinical trials also help improve the way cancer will be treated in the future. Even when clinical trials do not lead to effective new treatments, they often answer important questions and help move research forward.Patients can enter clinical trials before, during, or after starting their cancer treatment.
Some clinical trials only include patients who have not yet received treatment. Other trials test treatments for patients whose cancer has not gotten better. There are also clinical trials that test new ways to stop cancer from recurring (coming back) or reduce the side effects of cancer treatment.
Clinical trials are taking place in many parts of the country. See the Treatment Options section that follows for links to current treatment clinical trials. These have been retrieved from NCI's listing of clinical trials.Follow-up tests may be needed.
Some of the tests that were done to diagnose the cancer or to find out the stage of the cancer may be repeated. Some tests will be repeated in order to see how well the treatment is working. Decisions about whether to continue, change, or stop treatment may be based on the results of these tests.
Some of the tests will continue to be done from time to time after treatment has ended. The results of these tests can show if your condition has changed or if the cancer has recurred (come back). These tests are sometimes called follow-up tests or check-ups.
If the patient's blood cell counts are not too low and there are no signs or symptoms, treatment may not be needed and the patient is carefully watched for changes in his or her condition. If blood cell counts become too low or if signs or symptoms appear, initial treatment may include the following:
Check the list of NCI-supported cancer clinical trials that are now accepting patients with untreated hairy cell leukemia. For more specific results, refine the search by using other search features, such as the location of the trial, the type of treatment, or the name of the drug. Talk with your doctor about clinical trials that may be right for you. General information about clinical trials is available from the NCI website.
Treatment for progressive hairy cell leukemia may include the following:
Check the list of NCI-supported cancer clinical trials that are now accepting patients with progressive hairy cell leukemia, initial treatment. For more specific results, refine the search by using other search features, such as the location of the trial, the type of treatment, or the name of the drug. Talk with your doctor about clinical trials that may be right for you. General information about clinical trials is available from the NCI website.
Treatment of relapsed or refractory hairy cell leukemia may include the following:
Check the list of NCI-supported cancer clinical trials that are now accepting patients with refractory hairy cell leukemia. For more specific results, refine the search by using other search features, such as the location of the trial, the type of treatment, or the name of the drug. Talk with your doctor about clinical trials that may be right for you. General information about clinical trials is available from the NCI website.
For more information from the National Cancer Institute about hairy cell leukemia, see the following:
For general cancer information and other resources from the National Cancer Institute, see the following:
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A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
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PDQ® Adult Treatment Editorial Board. PDQ Hairy Cell Leukemia Treatment. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/leukemia/patient/hairy-cell-treatment-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389248]
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