Hairy cell leukemia is a type of hematologic cancer. This type of cancer starts in the tissues that form blood, such as the bone marrow, or in the cells of the immune system.

Hairy cell leukemia accounts for approximately 2 percent of all leukemias, is more common in men than in women, and is also more frequent in older people. Around 1,000 new cases are reported every year in the United States.

It is a rare form of leukemia, in which the bone marrow produces an excessive amount of a type of white blood cell called B cells. These abnormal B cells do not develop into healthy cells but instead become harmful cells known as leukemia cells.

Leukemia cells can build up in the blood or the bone marrow, taking up space from healthy cells. This may weaken the body’s immune system and make it more prone to infections, anemia, and bleeding.

The name “hairy” comes from the way the leukemia cells look under a microscope — they resemble hair.

Older men may have an increased risk of developing hairy cell leukemia.Share on Pinterest
Older men may have an increased risk of developing hairy cell leukemia.

Hairy cell leukemia progresses slowly, if at all. A person may have few or no symptoms in the early stages of the disease.

When symptoms appear, they may include one or several of the following:

  • frequent infections
  • fever
  • shortness of breath
  • fatigue or weakness
  • bone pain, particularly below the ribs
  • easy bruises
  • easy bleeding
  • enlarged liver or spleen
  • excessive sweating, particularly at night
  • lumps in the neck, underarm, stomach, or groin with no pain
  • weight loss for no known reason

The causes of hairy cell leukemia are not fully understood.

Doctors think that a mutation known as V600E in a specific gene is responsible for most cases of hairy cell leukemia. This gene is the BRAF gene.

Men and older people may have an increased risk of developing this disease.

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A slide showing hairy cell leukemia.
Image credit: National Cancer Institute, ID: 2159, 1985

A doctor may make a diagnosis of hairy cell leukemia based on physical exams, medical questions, and tests that look at the person’s blood and bone marrow cells.

Physical exam

A general body examination to check the person’s overall physical health for unusual signs or symptoms.

The exam may include searching for lumps or swelling that could be enlarged lymph nodes or signal an enlarged spleen or liver.

Medical history

Collecting information about the person’s health habits, past illnesses, and treatments.

Complete blood count (CBC)

A sample of blood is collected and examined to measure a variety of things:

  • amounts of red blood cells, white blood cells, and platelets
  • the amount of hemoglobin attached to red blood cells
  • the hematocrit, which is the proportion of the sample that is made up of red blood cells

Blood chemistry tests

Analysis of a blood sample to measure the levels of certain substances that are released by organs and tissues into the bloodstream. An unusually high or low amount of these substances can be a sign of a disease.

Peripheral blood smear

Checking a person’s blood sample under the microscope to look for changes in the shape of blood cells and the appearance of a “hairy” look. Doctors also check for the amount and type of white blood cells as well as the number of platelets.

Bone marrow aspiration or biopsy

Collection of a small sample of the person’s bone marrow, blood, or bone by inserting a hollow needle into the bone in the hip or breast area. This sample is then examined under the microscope to look for “hairy” leukemia cells, and to track healthy blood cells.

Cytogenetic analysis

Analysis of tissue cells under the microscope to look for genetic abnormalities.


Analysis of markers on the surface of blood or bone marrow cells. Doctors will compare these with healthy cells of the immune system to determine what type of cells they are.

Flow cytometry

Tests a blood sample to estimate the number of cells, and the percentage of living cells it contains. The sample can also reveal other characteristics of cells, including the size, shape, and presence of tumor markers on the cell surface.

For this test, cells are stained with a fluorescent dye and suspended in a liquid. By passing a light beam through the cells, a doctor can identify their characteristics by the way the cells scatter light.

Computed tomography (CT) scan

A test that consists of making several X-ray images, from different angles, of specific body areas. A dye may sometimes be swallowed or infused into the person’s veins so that a doctor can see the organs and tissues more clearly.

A CT scan of the chest, abdomen, or pelvis may be performed to look for swollen lymph nodes or a swollen spleen.

Gene mutation test

A laboratory test that examines a blood or bone marrow sample to look for mutations in the BRAF gene. This gene is mutated in around 80–90 percent of people with hairy cell leukemia.

Hairy cell leukemia progresses slowly, and so some people survive for many years without receiving treatment.

When treatment is necessary, treatment options can depend on several factors, such as:

  • how far the leukemia has developed
  • the proportion of leukemia cells to healthy blood cells in the blood and bone marrow
  • the presence of a swollen spleen
  • the presence of signs or symptoms of leukemia, such as infections
  • the return of the leukemia after the previous treatment
  • the person’s age, level of fitness, and general health status

Different types of treatment are available to people with hairy cell leukemia. These include standard treatments used in clinical practice and treatments that are studied in clinical trials.

Here are five different types of standard treatments currently being used:

1. Watchful waiting

Careful monitoring of the person’s condition to watch for new signs or symptoms before deciding that it is necessary to start treatment.

2. Surgery

A surgical procedure, known as splenectomy, to remove the spleen.

With the emergence of new effective treatment options, this procedure is now rarely used. It may be used to treat pregnant women to delay the use of other treatments, such as chemotherapy.

3. Chemotherapy

A type of therapy that stops the progression of cancer by killing cancer cells or stopping them from dividing.

Depending on the type and stage of the cancer, chemotherapy can be given orally or injected.

The chemotherapy drugs cladribine and pentostatin are the standard first-line treatments for hairy cell leukemia. Bendamustine is another chemotherapy drug that can be used in people who get worse after the initial treatment.

4. Biologic therapy

Also known as immunotherapy, biologic therapy is a type of treatment that uses the body’s own immune system to fight cancer.

Alpha-interferon is one type of biologic agent used to treat hairy cell leukemia.

5. Targeted therapy

A form of treatment that recognizes and attacks cancer cells without harming healthy cells.

Targeted therapy includes the use of monoclonal antibodies, which are molecules made in the laboratory that identify and attach to substances on cancer cells or substances that help cancer cells grow. Doing so prevents cancer from growing or spreading.

In hairy cell leukemia, rituximab is a commonly used monoclonal antibody. Others, such as obinutuzumab and ofatumumab, are being studied.

Other targeted therapies that doctors use for people with mutations in the BRAF gene are ibrutinib and vemurafenib.

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Acupuncture may help to relieve nausea brought on by chemotherapy.

Natural treatment options cannot cure hairy cell leukemia. However, some may help people deal with their disease or with the side effects of treatment.

Natural treatments that may help include:

  • Acupuncture: a procedure where fine needles are inserted in specific body points to relieve nausea and vomiting caused by chemotherapy.
  • Massage: therapeutic manipulation and application of pressure to body tissues and muscles to reduce anxiety and fatigue.
  • Mind-body therapies: guided meditation and relaxation techniques to help relax and relieve pain.
  • Aromatherapy: the use of fragrant oils to give a sense of well-being and relieve stress. These substances can be directly massaged into the skin, added to bath water, or heated to release their scent.

Treatment of hairy cell leukemia has a high rate of success, and most people have a similar life expectancy to healthy people of the same age. However, people below 40 years old may have a lower life expectancy compared with people of the same age.

Hairy cell leukemia is considered a chronic cancer, as it never completely goes away. However, most people with the disease usually experience an extended period with few or no symptoms after the initial treatment.

Once a person is in remission, they will still require follow-up visits with their doctor to monitor blood counts and their health condition. If a person gets worse or sees their disease come back, they can be retreated and enter another remission.

A person’s chances of recovering from hairy cell leukemia depend on whether the disease responds to treatment, and on whether it does not progress or progresses so slowly that it does not require treatment.