Hairy cell leukemia is a cancer of the blood and bone marrow. It gets its name from the “hairy” appearance of its cancer cells.

Treatment for hairy cell leukemia will depend on the cancer’s progression. Treatment options include surgery, chemotherapy, and biologic and targeted antibody therapy.

This article outlines what hairy cell leukemia is, its symptoms and causes, and what treatment options are available.

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Hairy cell leukemia is a rare form of leukemia in which the bone marrow produces an excessive amount of B cells, a type of white blood cell. These atypical B cells develop into harmful 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 term “hairy” comes from how the leukemia cells look under a microscope — they resemble hair.

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

Hairy cell leukemia progresses slowly. 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
  • shortness of breath
  • fatigue or weakness
  • bone pain, particularly below the ribs
  • easy bruises
  • easy bleeding
  • lumps in the neck, underarm, stomach, or groin with no pain
  • unintentional weight loss

The causes of hairy cell leukemia are not clear. However, the BRAFV600E gene mutation may play a role in developing the disease. This mutation is an indicator of hairy cell leukemia and is present in 80–90% of patients.

Researchers in a 2021 study referred to the BRAFV600E mutation as “the genetic lesion underlying HCL.”

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

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

To diagnose the disease, a doctor may perform any of the following tests.

Physical exam

This is 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.

Doctors will also assess a person’s medical history.

Complete blood count

During a complete blood count, a doctor will take a blood sample and assess any of the following:

  • 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 red blood cells

Learn more about complete blood counts here.

Blood chemistry tests

This test involves the analysis of a blood sample to measure the levels of substances in the bloodstream. A doctor can use a blood chemistry test to check a person’s:

Peripheral blood smear

During this test, a medical professional will check a blood sample under the microscope to look for changes in the shape of blood cells and to look for a “hairy” appearance. Doctors also check for the amount and type of white blood cells and the number of platelets.

Learn more about the different types of blood tests here.

Bone marrow aspiration or biopsy

A doctor may take a small sample of the person’s bone marrow to analyze for the presence of hairy leukemia cells. They may also assess general bone marrow health and blood cell production.

Learn more about bone marrow biopsies here.

Gene mutation test

This test examines a blood or bone marrow sample to look for mutations in the BRAF gene. It is an important diagnostic tool for confirming hairy cell leukemia.

Cytogenetic analysis

During this test, a medical professional will analyze blood, bone marrow, or other tissue samples to look for changes in chromosomes. Cytogenetic analysis can reveal broken, additional, or missing chromosomes, which may signify different cancers and genetic diseases.


In immunophenotyping, doctors use antibodies to determine the presence or absence of white blood cell antigens. These antigens typically form on the surface of white blood cells. Unusual formations of these antigens can indicate leukemias and lymphomas.

Learn about the differences between leukemias and lymphomas here.

Flow cytometry

In flow cytometry, a medical professional 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.

CT scan

A CT scan consists of several X-ray images from different angles of specific body areas. Doctors may inject a special dye into the person’s veins so that a doctor can see the organs and tissues more clearly.

Hairy cell leukemia often progresses slowly and does not progress at all in some cases. When treatment is necessary, treatment options can depend on several factors, such as:

  • how far 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 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.

  • Watchful waiting: This involves careful monitoring of the person’s condition to watch for new signs or symptoms before deciding that it is necessary to start treatment.
  • Chemotherapy: Chemotherapy uses drugs to stop cancer cells from growing and dividing to make more cells.
  • Immunotherapy: This type of treatment helps the person’s immune system fight leukemia cells. There are various types of immunotherapy.
  • Targeted therapy: This therapy uses drugs to target certain genes and proteins involved in the growth of cancer cells. Doctors may recommend targeted therapy for use alongside chemotherapy or in its place.
  • Surgery: If a person’s spleen enlarges and causes adverse symptoms, doctors may perform surgery to remove it. However, this is extremely uncommon.

Natural treatment options cannot cure hairy cell leukemia. However, some home treatments may help people manage the symptoms of leukemia and its treatments. Options include:

  • Acupuncture: In this procedure, a licensed professional inserts fine needles into specific body points to relieve nausea and vomiting caused by chemotherapy.
  • Massage: Therapeutic manipulation and application of pressure to body tissues and muscles help reduce anxiety and fatigue.
  • Mind-body therapies: These are guided meditation and relaxation techniques that can help a person relax and manage pain symptoms.
  • Aromatherapy: Aromatherapy uses the smell of fragrant oils to give a sense of well-being and relieve stress. Some people may find that aromatherapy helps them relax.

Learn more about natural treatment options for leukemia symptoms here.

Hairy cell leukemia develops slowly, and treatment can manage the condition for many years. However, it is still a chronic cancer, as it never completely disappears.

Treatment can help a person sustain periods of remission. These are times when there are little or no signs of cancer or its symptoms.

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 their overall health status.

Hairy cell leukemia is a rare type of blood and bone marrow cancer. Chemotherapy, immunotherapy, and targeted drug programs can help manage the condition.

A person’s outlook will depend on the progression of the disease at diagnosis, how it responds to treatment, and their overall health status. Typically, the outlook for people with hairy cell leukemia is positive with proper, prompt treatment.