Definition and Overview

Hairy cell leukaemia (HCL) is a rare type of chronic leukaemia (cancer of the blood) that develops from B lymphocytes or B cells.

The condition is named as such because the cancer cells appear to have hair-like outgrowths on their surface when viewed under a microscope. HCL develops when the bone marrow produces excessive amounts of B cells, which restricts the normal production of healthy platelets and white and red blood cells.

Unlike other types of cancer, HCL progresses very slowly, does not metastasise (spread), and in many cases, remains stable for many years. It is also very rare, affecting approximately 500 people in the United States every year. For unknown reasons, it is more common in men than women.

HCL is treatable but cannot be cured. Treatment is not always necessary but if symptoms develop (such as low blood cell counts, recurrent infections, or a swollen spleen), chemotherapy and biological therapy are initiated. The use of chemotherapy drugs often results in prolonged disease remission and restoration of the patient’s normal quality of life. The survival rating for patients who have undergone hairy cell leukaemia treatment is not significantly different from those who do not have HCL. However, about 40% of patients experience relapses after about ten years of successful treatment. When this happens, they undergo the same therapies but the remissions tend to last for a shorter period following retreatment.

Causes of Condition

In general, malignant cells develop as a result of errors in the DNA. In the case of HCL, the abnormal changes in the DNA affect the bone marrow causing it to produce defective white blood cells.

Certain factors that are thought to increase the risk of HCL are the following:

  • Previous cancer treatment (radiotherapy) for another type of cancer

  • Exposure to certain chemicals and sawdust

  • Age - HCL is commonly diagnosed in people over 30 years old

  • Gender - Eight out of ten HCL sufferers are men

Key Symptoms

HCL progresses very slowly. In its early stages, its symptoms are either non-existent or very minor that they are often ignored.

HCL symptoms are often observed when other organs are involved and secondary complications arise.

  • Anaemia or low red blood cell count, resulting in weakness, fatigue, dizziness and shortness of breath

  • Low white blood cells count, which increases the risk of infections

  • Low platelet count, which can result in spontaneous bleeding and increased bruising

  • Enlarged spleen, which can result in pain, difficulty eating, and spleen rupture

  • Pain in the right side of the abdomen if there’s liver involvement

  • Weakened immune system

Rare HCL symptoms include:

  • Unusual infections due to pathogens that affect the brain, skin, liver, and lungs

  • Painful rash due to herpes zoster

  • Severe headaches and confusion, if there’s brain involvement

  • Increased joint pain and swelling

Who to See and Types of Treatments Available

Hairy cell leukaemia is diagnosed with these tests and procedures:

  • Physical examination, to determine if the spleen is enlarged

  • Computed tomography (CT) scan of the abdomen

  • Blood tests

  • Blood smear - Detects the presence of malignant cells in blood samples observed under a microscope

  • Bone marrow biopsy - Involves taking a small sample of bone marrow tissue to identify any blood cell abnormalities

Patients diagnosed with hairy cell leukaemia are referred to a haematologist-oncologist, a doctor who specialises in the diagnosis, treatment, and management of blood cancers.

Treatment is not automatically recommended following HCL diagnosis. Often, doctors advise watchful waiting especially when there are no apparent symptoms. This “watch and wait” surveillance approach is preferred because the risk of the cancer progressing is very minimal. Thus, exposing patients to chemotherapy drugs when not absolutely needed may not be beneficial.

However, if the immune system is severely compromised or unable to effectively fight infections, chemotherapy is initiated right away. The great majority of people who receive a continuous infusion of chemotherapy drugs for about three to six months experience partial or complete remission. However, chemotherapy drugs have side effects including fever, infection, and nausea.

Biological therapy, which strengthens the immune system to fight HCL, is recommended for patients who cannot tolerate chemotherapy drugs. Most people experience partial remission after taking a drug called interferon for a full year. Just like chemotherapy, biological therapy also has side effects including fatigue and fever.

A surgery called splenectomy can be part of HCL treatment. The procedure, which goal is to remove an enlarged or ruptured spleen, is now commonly performed on an outpatient basis using a minimally invasive method (laparoscopic splenectomy) in which a tiny video camera (laparoscope) and special surgical tools are used. Since the procedure does not require a large incision in the abdomen, the risks of scarring and infection are minimised.

Patients whose spleen has been removed have an increased risk of infection and are thus vaccinated against meningitis, pneumococcal infection, and Haemophilus infections. They should also have a supply of antibiotics that they can immediately take at the first sign of infection.


  • Tallman MS, et al. Clinical features and diagnosis of hairy cell leukaemia.

  • Hairy cell leukaemia treatment (PDQ): Health professional version. National Cancer Institute. /HealthProfessional/page1.

  • https://www.hairycellleukaemia .org/about-hcl/treatment/

  • Naik, R. R. & Savin, A. (2012 Jan) My Treatment Approach to Hairy Cell Leukaemia . Mayo Clin Proc, 87(1) 67-76.

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