A rare subtype of chronic lymphocytic leukemia, hairy cell leukemia, gets its name from the way white blood cells look under a microscope when sampled from patients with this condition. In the case of hairy cell leukemia, abnormal changes in certain white blood cells known as B lymphocytes cause thin, hair-like projections on the cells’ surfaces. As with other types of leukemia, health problems arise when the bone marrow produces so many hairy cells that they prevent normal blood cells from developing.

Hairy cell leukemia is a disease that occurs in adults—it’s almost never diagnosed in children. According to the National Organization for Rare Disorders (NORD), an estimated 6,000 Americans have hairy cell leukemia, accounting for about 2% of adult leukemia cases in the U.S. Approximately 600 to 800 new cases are diagnosed each year.

If you have been diagnosed with leukemia, Moffitt can help. Request an appointment with one of our experts today.

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If you’ve been diagnosed with hairy cell leukemia or you’re concerned that you might have symptoms of this type of blood cancer, you can feel confident seeking care at Moffitt Cancer Center. The multispecialty team of our Malignant Hematology Program has vast experience in diagnosing and treating all types of leukemia. Connect with us today if you’d like more information or to request an appointment with one of our leukemia specialists.

What are the signs and symptoms of hairy cell leukemia?

This type of leukemia typically progresses slowly and sometimes remains stable for a long time. However, after years of overproduction, hairy cells can build up in the blood and bone marrow, crowding out healthy white blood cells, red blood cells and platelets. This can make the patient more susceptible to infection. It can also cause anemia, easy bleeding and potentially swelling of the spleen.

As a result, typical hairy cell leukemia symptoms include:

Weakness and chronic fatigue
Easy bruising or bleeding
Frequent infections
Shortness of breath
Fever or night sweats
Unintentional weight loss
Pain or an uncomfortable feeling of fullness below the ribs
Painless lumps in the neck, stomach, underarm or groin areas

It’s important to remember that many of the symptoms of hairy cell leukemia can also be signs of other common health conditions. You should consult with your doctor if you are experiencing the symptoms listed above.

Older male patient with hairy cell leukemia

What causes hairy cell leukemia?

The exact cause of hairy cell leukemia is unknown. As with other types of cancer, it occurs when cells mutate and begin to grow uncontrollably. Some studies have associated the development of hairy cell leukemia with the use of certain farming chemicals.

Apart from that, few risk factors have been identified. Hairy cell leukemia can affect people as young as 20, but most people diagnosed with the disease are 50 or older. Additionally, men are far more likely to develop this type of cancer than women.

Approx. 600 to 800

new cases of hairy cell leukemia diagnosed yearly in the U.S.
Estimated 6,000

Americans have hairy cell leukemia

How is hairy cell leukemia diagnosed?

When abnormal hairy cells leave the bone marrow and circulate through the bloodstream, they typically collect in the spleen, which is a small organ on the upper left side of the stomach. The spleen’s job is to filter and remove worn-out blood cells. However, over time, the accumulation of hairy cells can cause the spleen to swell and cause discomfort.

Physicians can often feel the enlarged spleen during a physical exam. This may prompt them to order blood tests that will lead to a hairy cell leukemia diagnosis. In other cases, anomalies in the results of a routine complete blood count (CBC) test might lead to follow-up testing that confirms a diagnosis of hairy cell leukemia.

Additional diagnostic tests may include:

Peripheral blood smear, which involves analysis of blood cells under a microscope
Immunophenotyping, a process that uses antibodies to identify cells based on the markers present on the cells’ surface
Bone marrow biopsy, which involves the removal and testing of a small bone marrow sample
Scans of the patient’s belly area using ultrasound or computerized tomography (CT) imaging
Flow cytometry, which can identify hairy cells by a surface protein pattern that does not occur in healthy B lymphocytes

What are the treatment options for hairy cell leukemia?

As with all cancers, the best treatment for hairy cell leukemia depends on many factors, including the patient’s age, overall health and the specific characteristics of their leukemia cells. For many patients with hairy cell leukemia, the cancer’s progress is so slow that it produces few, if any, symptoms or complications. For these patients, the only treatment required may be careful monitoring of their condition, also known as “watchful waiting.”

Another common treatment for hairy cell leukemia is chemotherapy, or the use of drugs to kill cancer cells or stop them from reproducing. Two common anticancer drugs used in chemotherapy for hairy cell leukemia are cladribine and pentostatin.

Some other treatments a cancer specialist might recommend include immunotherapy and targeted therapy. In some cases, a patient with an enlarged spleen caused by hairy cell leukemia may have surgery to remove the organ.

Hairy cell leukemia prognosis

The prognosis for people who receive proper treatment for their hairy cell leukemia is excellent, thanks largely to advances in chemotherapy that occurred in the 1980s and ‘90s. In fact, some recent studies indicate that most people with this form of leukemia can look forward to a normal lifespan.

At present, there’s no cure for hairy cell leukemia. Like all cancers, it can come back after years of remission. However, many patients receive effective second-line treatments that help them live many years more after their cancer relapse.

Hairy cell leukemia FAQs

If you've been diagnosed with HCL, you likely have questions about what comes next, especially regarding the unique "watchful waiting" period and the high success rates of the available drug therapies. Our experts at Moffitt Cancer Center have compiled answers to some common questions they're asked about HCL's signs, diagnosis, and long-term prognosis to provide you with some clarity and the confidence you need to manage this journey.

What exactly is Hairy Cell Leukemia, and where does the name come from?

Hairy Cell Leukemia (HCL) is a rare, slow-growing subtype of chronic lymphocytic leukemia that affects the white blood cells. It's so rare that it only accounts for about 2% of adult leukemia cases. HCL's name comes from how the abnormal white blood cells (B lymphocytes) look under a microscope - they have thin, hair-like projections on their surfaces.
What are the most common signs and symptoms of HCL?
HCL symptoms arise when the abnormal "hairy cells" multiply in the bone marrow and crowd out healthy red cells, white cells, and platelets. This often leads to:
- Catching infections frequently because you have a shortage of normal white blood cells
- Feeling weak and chronically tired due to anemia, which is a low red blood cell count
- Noticing easy bruising or bleeding that results from a low platelet count
- Having pain or an uncomfortable fullness below your ribs, which can signal an enlarged spleen
Other common signs can include fever, night sweats, or unexpected weight loss.
Do I need treatment for HCL right away, or is "watchful waiting" an option?

Treatment is not always required immediately. Because HCL often progresses very slowly and may produce few or no symptoms, a period of "watchful waiting" is a common initial approach. Treatment typically begins only when the leukemia starts to cause symptoms, infections, low blood counts, or other complications.
What is the long-term prognosis for Hairy Cell Leukemia, and is it curable?

The prognosis for patients with HCL who receive proper treatment is excellent. While HCL is not yet considered curable, advances in chemotherapy have led to highly effective remissions. Many recent studies indicate that most people with this form of leukemia can look forward to a normal lifespan. Like most cancers, HCL can relapse, but effective second-line treatments are available to manage the disease long-term.
What are the main treatment methods for Hairy Cell Leukemia?
Treatment is always tailored to your specific needs, but the goal is generally to use powerful drugs to achieve a deep and lasting remission. The main approaches include:
- Chemotherapy: This is the most common and effective method. Chemotherapy drugs work to destroy the hairy cells in your system. This often leads to a long-term remission.
- Targeted and Immunotherapy: Advanced drug types may be used to specifically target the cancer cells or enlist your own immune system to help fight the leukemia.
- Surgery (Splenectomy): If the buildup of hairy cells causes your spleen to become severely swollen and painful, your doctor may recommend surgery to remove the organ and immediately relieve those symptoms.

Treatment for hairy cell leukemia at Moffitt Cancer Center

The leukemia specialists in the highly regarded Malignant Hematology Program at Moffitt take an individualized, patient-centric approach to the diagnosis and treatment of blood cancers. As the only Florida-based Comprehensive Cancer Center designated by the National Cancer Institute, we offer advanced screening and treatment options that aren’t available at all cancer hospitals.

Moreover, many of our patients benefit from access to clinical trials aimed at testing the effectiveness of new treatments and preventing leukemia recurrence. Our robust clinical trials program and personalized approach to leukemia treatment are just two of the ways we’re continually improving patient outcomes and enhancing our patients’ quality of life.

When you entrust your care to Moffitt, you will be a top priority of a cancer center that delivers nationally-ranked care in new and transformative ways. One of the ways we deliver this high level of care is by connecting every new patient with a cancer expert as soon as possible. Connect with us today by calling 1-888-663-3488 or filling out our convenient online new patient registration form. A referral is not required.

References

National Cancer Institute – Hairy Cell Leukemia Treatment
National Organization for Rare Disorders (NORD) – Hairy Cell Leukemia
Hairy Cell Leukemia Foundation – Understanding Hairy Cell Leukemia
National Institutes of Health – Hairy Cell Leukemia Patients Have a Normal Life Expectancy
Federal Register – Diseases Associated With Exposure to Certain Herbicide Agents

Leukemia

Hairy Cell Leukemia