Hairy cell leukemia

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at February 16, 2016
StartDiseasesHairy cell leukemia

Hairy cell leukemia (HCL) is a rare type of blood cancer that affects fewer than 1 in every 10,000 people. It usually develops slowly and can be kept under control for many years with proper treatment. Many people diagnosed with this condition can expect to have a normal length of life.


Definition & Facts

Hairy cell leukemia is a cancer of the blood in which your bone marrow produces too many lymphocytes, or B cells, which are a type of white blood cell that fights infection. This cancer is rare, slow-growing, and gets its name from the fine projections extending from the surface of the abnormal cells, giving them a “hairy” appearance when viewed under a microscope.

HCL affects more men than women and is most common in middle-aged and older adults. While treatment is very effective at causing the cancer to go into remission, it is a chronic condition that may never be completely cured.

Symptoms & Complaints

Many people with hairy cell leukemia will not show any symptoms and may only discover their condition while undergoing a blood test for a separate illness or routine medical exam. People who do show symptoms may complain of the following:

Symptoms are generally mild at first and build up slowly. These symptoms can often be attributed to other causes besides hairy cell leukemia so it is important to be evaluated by a doctor.


Like with many cancers, doctors are unsure of the causes of hairy cell leukemia. Genetic mutations in DNA cause bone marrow stem cells to create too many improperly functioning white blood cells. However, doctors do not know what causes the initial mutation of a patient’s DNA.

Certain factors are thought to increase a person’s risk of developing the disease. These include exposure to environmental toxicants such as radiation, chemicals, or sawdust. Ethnicity may also be a factor as the disease appears to affect men of Ashkenazi Jewish decent more than any other group. However, studies into these linkages have proven inconclusive.

Diagnosis & Tests

Hairy cell leukemia must be diagnosed by a medical professional. Based on a patient’s symptoms, a doctor may perform a physical examination to determine if a patient’s spleen and/or lymph nodes are enlarged. This can also be detected using a computerized tomography scan, or CT scan which shows a detailed image of the inside of a patient’s body.

Blood tests such as a complete blood count, or CBC, may be performed to determine the levels of red blood cells and white blood cells and platelets in a patient’s blood. A person with hairy cell leukemia will have low levels of all three of these cells. Doctors may also perform another type of blood test called a peripheral blood smear which enables the “hairy” blood cells characteristic of the disease to be seen under a microscope.

Lastly, a bone marrow biopsy may be performed. During this procedure, a small amount of bone marrow is removed from a patient’s hip. This sample is then examined for abnormal cells.

Following diagnosis, HCL is divided into three groups; untreated, progressive, and relapsed or refractory. Untreated is when hairy leukemia cells are detected in the bone marrow and blood, blood counts may be low, and the spleen may be enlarged but no treatment is necessary. Progressive HCL is when the condition still exists after a round of treatment. Relapsed is when the condition goes into remission after treatment but then returns, and refractory is when it does not respond to treatment.

Treatment & Therapy

Many people will wait until they begin to show signs before they seek treatment. The majority of people diagnosed with this condition will require treatment at some point. There is no cure for hairy cell leukemia, but current treatments are highly effective at managing it.

The first treatment option most patients receive is chemotherapy which is given through a direct infusion into the bloodstream. Cladribine is the most common chemotherapy drug for hairy cell leukemia. It is given one time through a continuous infusion over the course of several days. People who receive cladribine will often go into remission for several years before they require another treatment. Common side effects include fever and infection.

Pentostatin is another common chemotherapy treatment for hairy cell leukemia. Unlike cladribine, infusions are given every other week for three to six months. Remission rates for both drugs are similar, and common side effects include fever, infection, and nausea.

Patients may also receive biological therapy which attempts to make cancer cells more recognizable to the immune system and therefore cause the body to destroy the abnormal cells. Biological treatments are limited and less effective than chemotherapy, but they are a good option for patients who do not tolerate chemotherapy well or for whom chemotherapy has not been effective. The two types of treatment used are interferon and rituximab. Both may cause the condition to go into partial remission, and common side effects are flu-like symptoms.

The last treatment option is a splenectomy, a surgical procedure in which the spleen is removed. This is not a common treatment, but it may be helpful in a patient whose spleen has ruptured or is enlarged and causing pain. A splenectomy is often effective for restoring normal blood counts, but it is not considered a cure.

Prevention & Prophylaxis

Since its cause is unknown, there is no way to prevent hairy cell leukemia. Hairy cell leukemia is a rare blood cancer that grows slowly and generally causes mild, if any, symptoms. Treatments such as chemotherapy are highly effective, and patients can expect to maintain a normal quality of life in most cases.