Hairy cell leukemia
Hairy cell leukemia is a rare, chronic cancer that affects the blood and bone marrow, primarily in adults over the age of forty. It is characterized by the presence of abnormal B lymphocytes, which develop threadlike projections making them appear "hairy" under a microscope. This cancer leads to a decrease in the production of normal blood cells, resulting in conditions such as anemia, thrombocytopenia, and increased susceptibility to infections. Symptoms often develop gradually and may include fatigue, easy bruising, abdominal bloating due to spleen enlargement, and unexplained weight loss.
The disease is usually diagnosed through a combination of physical examinations, blood tests, and a biopsy of bone marrow. Though the exact cause of hairy cell leukemia is not known, certain risk factors such as family history, Ashkenazi Jewish heritage, and exposure to certain toxins may increase the likelihood of developing the disease. Treatment typically involves chemotherapy, which can lead to remission in a significant number of cases. Some patients may also receive biological therapies or surgical intervention if necessary. Despite its slow progression, untreated hairy cell leukemia can lead to serious health complications, but with appropriate management, many patients can achieve long-lasting remission.
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Hairy cell leukemia
ALSO KNOWN AS: Leukemic reticuloendotheliosis
RELATED CONDITIONS: Anemia, thrombocytopenia (excessive bleeding and bruising), neutropenia, splenomegaly
DEFINITION: Hairy cell leukemia is a rare, chronic, slow-progressing cancer of the blood and bone marrow that is most often found in people over age forty and does not occur in children.
Risk factors: Although there is some debate about the role of risk factors in hairy cell leukemia, the following appear to increase the likelihood of developing this cancer: a family history of blood cancers, Ashkenazi Jewish heritage, a previous diagnosis of cancer, and exposure to radiation, sawdust, and toxins, especially those in agricultural chemicals and petrochemicals.
Etiology and the disease process: Researchers have not yet determined exactly what changes in deoxyribonucleic acid (DNA) cause the development of hairy cell leukemia. They do know that hairy cell leukemia begins in the bone marrow. The bone marrow makes stem cells that develop into three types of blood cellsred blood cells, white blood cells, and platelets. Hairy cell leukemia is a defect in white blood cell production.
White blood cells are part of the immune system. Their function is to produce antibodies (proteins) and fight infection. Hairy cell leukemia affects the type of white blood cells called lymphocytes. There are three kinds of lymphocytes. In response to foreign organisms (bacteria, viruses, fungi), B lymphocytes produce antibodies that help destroy these foreign organisms. They are aided by T lymphocytes and natural killer (NK) cells. All three types of lymphocytes must function adequately to control infections.
Too many stem cells can become B lymphocytes in people with hairy cell leukemia. These B lymphocytes develop abnormal threadlike projections that make them look “hairy.” Hairy lymphocytes are defective and do not function correctly in fighting infections. Because an abnormally large number of stem cells turn into hairy B lymphocytes, the number of other blood cells is smaller than usual. A decrease in red blood cells leads to anemia. A decrease in platelets makes it difficult for the blood to clot. The increase in hairy B lymphocytes occurs gradually and produces no noticeable signs at the start of the disease. As the bone marrow produces more defective B lymphocytes, these cells collect in the spleen and sometimes in the liver. The spleen begins to swell and become tender.
Incidence: Between 800 and 1,000 people in the United States are newly diagnosed with hairy cell leukemia yearly. Five times more men than women develop this cancer. Most are diagnosed in their early fifties, though some are diagnosed in their seventies.
Symptoms: Hairy cell leukemia usually produces gradual, very general symptoms that initially are not very noticeable. A decrease in red blood cells causes anemia, which results in unusual tiredness, weakness, and shortness of breath. A decline in platelets causes easy bruising and difficulty getting blood to clot. Defective B lymphocytes lead to increased infections and sometimes a low-grade fever associated with chronic infection. The individual may feel bloating or tenderness below the ribs. This is caused by spleen swelling (splenomegaly) as masses of hairy B lymphocytes collect there and sometimes in the liver. Individuals may lose weight for no apparent reason.
Screening and diagnosis: Hairy cell leukemia is rare, so there are no routine screening tests for this cancer. Most people first see a physician for anemia symptoms or repeated infections due to malfunctioning B lymphocytes. Hairy cell leukemia is usually discovered during testing to determine the cause of these symptoms.
Diagnosis of hairy cell leukemia begins with a physical examination. About 80 percent of people with hairy cell leukemia have a spleen so enlarged that the physician can feel it by pressing on (palpating) the abdomen. However, an imaging scan (computed tomography, ultrasound) may be done to determine the size of the spleen, especially if the individual complains of bloating and tenderness. A complete blood count (CBC) determines the number and type of blood cells. If the lymphocyte count is high, a peripheral blood smear is done. This test looks at a thin layer of blood under a microscope to check for abnormal or “hairy” cells. About 20 percent of people with hairy cell anemia show abnormalities on liver function tests.
Diagnosis continues with a bone and bone marrow biopsy. Under local anesthetic, a small piece of bone and marrow is removed from the hip bone and examined in the laboratory for cancer cells. A definitive diagnosis of hairy cell leukemia comes from studying the pattern of proteins on the surface of B lymphocytes under the microscope. This is called immunophenotyping, and it helps distinguish between hairy cell leukemia and other blood cancers.
Since hairy cell leukemia is a chronic, slow-growing cancer, it is not staged using the standard TNM (tumor/lymph node/metastasis) system. The staging of hairy cell leukemia is as follows:
- Untreated or newly diagnosed hairy cell leukemia: Hairy B lymphocytes are found in the blood and bone marrow. Other blood cell levels may be decreased, and the spleen is enlarged.
- Progressive hairy cell leukemia: The cancer has been treated with chemotherapy or removal of the spleen (splenectomy). There is an increased number of hairy cells, or other blood cell levels are below normal.
- Relapsed or refractory hairy cell leukemia: Hairy cell leukemia has returned after treatment (relapsed) or has not responded to treatment (refractory).
Treatment and therapy: Because hairy cell leukemia progresses very slowly and sometimes not at all, the patient and physician may decide to wait and monitor the blood to see if conditions worsen. Early treatment, although imperative for most other cancers, does not improve the chance for remission, survival, or cure, so if symptoms are manageable, waiting does not harm the patient. Eventually, most people need treatment, but some individuals go ten or more years before treatment becomes necessary.
One course of chemotherapy puts as much as 85 percent of hairy cell leukemia cases into complete remission and the remainder in partial remission. Remission is a condition in which symptoms disappear, but the cancer is still present in the body and can reoccur. The chemotherapy drug of choice is cladribine (Leustatin), and the alternative is pentostatin (Nipent).
About 10 percent of patients do not improve with chemotherapy, and others have health conditions that prohibit chemotherapy treatments. These individuals may receive biological therapy (immunotherapy). Biological therapy aims to boost the immune system and make cancer cells more recognizable to healthy immune system cells so that they will be destroyed. Interferon alpha and rituximab (a monoclonal antibody made in the laboratory) are the standard biological therapies for hairy cell leukemia. Biological therapy is frequently successful in bringing about remission.
If the spleen is so enlarged that it may burst, surgery to remove it is necessary. This does not cure hairy cell leukemia but does restore the blood count to normal, which helps the body fight infection.
Prognosis, prevention, and outcomes: Hairy cell leukemia rarely is chronic, but it can be put into remission through treatment. Remission can last many years before symptoms recur. Recurring symptoms are often successfully treated. The overall five-year survival rate for individuals who receive treatment is about 90 percent, with more than half of individuals showing no progression of symptoms. About 17 percent of people with hairy cell leukemia eventually go on to develop other types of cancer, and those who do not receive treatment usually die within four years of diagnosis.
Bibliography
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