Hairy Cell Leukemia 101 : Symptoms, Causes, Stages & Treatment

Hairy cell leukemia is a rare type of blood cancer that begins when the bone marrow produces too many B cells (lymphocytes). Find out more about its symptoms, survival rates, causes, stages, and treatment options.

by Calvyn Ee

What is Hairy Cell Leukemia (HCL)?

Hairy cell leukemia, commonly abbreviated as HCL, is a type of cancer of the blood, which begins in the bone marrow. It is called hairy cell leukemia due to the thin, hair-like projections seen on the leukemia cells when viewed under a microscope. It is also a rare form of cancer, with a higher prevalence in men (four times higher compared to women), especially those above the age of 50. However, it may still occur in men between the ages of 20 to 80. Due to its rarity, HCL makes up 2% of all leukemias diagnosed.

Our body produces healthy blood cells from the bone marrow. There are three types of healthy blood cells:

  • Red blood cells, which deliver oxygen to the entire body
  • White blood cells, which fight off infections
  • Platelets, which help in clotting to prevent blood loss from cuts, wounds, etc.

HCL occurs where the bone marrow creates an abundance of defective white blood cells, which are also called leukemia cells. As these defective cells multiply uncontrollably, the bone marrow becomes ‘flooded’ and there is not enough space for healthy blood cells. This shortfall of healthy blood cells is known as pancytopenia.

The leukemia cells will then invade the bone marrow, liver and spleen. This causes a number of complications, which are further compounded by the reduced number of healthy blood cells in the body.

Hairy cell leukemia is incurable, but available treatment options allow patients to live long and fruitful lives.

Symptoms of Hairy Cell Leukemia (HCL)

The symptoms of HCL may appear gradually over time. Because of how it affects the bone marrow and its production of healthy blood cells, a number of symptoms will crop up based on the reduction of healthy blood cells.

Decreased red blood cells lead to anaemia, where not enough oxygen is supplied to the entire body, leading to increased tiredness, fatigue, shortness of breath, and/or dizziness.

Decreased white blood cells can lead to a weaker immune system, as there are not enough white blood cells to fight off infections. This can lead to recurring fevers and other illnesses that may further compromise your overall health.

Decreased platelet counts, or thrombocytopenia, can be life-threatening, as there are not enough platelets to form blood clots whenever you are cut or wounded. This may also present itself as nosebleeds, bleeding gums, bruising easily, or even severe stomach bleeding.

Because of how the leukemia cells also travel to other parts of the body, other symptoms may be present. In some cases, there occurs an enlargement of the spleen, called splenomegaly, sometimes enlarging to two to three times its normal size. Persons with HCL may have abdominal pains where the spleen is located, a feeling of fullness in the stomach, or severe pain.

The liver and lymph nodes can also be adversely affected and may also be enlarged. The enlargement of the liver is known as hepatomegaly, leading to pain on the right side of your body, abnormal liver functions, or accumulation of fluids in the abdomen.

There are other complications that may arise from HCL. However, the variety of symptoms, coupled with the rarity of HCL and its slow onset, can make an accurate diagnosis difficult.

Causes of Hairy Cell Leukemia (HCL)

The exact causes of HCL are not readily understood, partly due to its rarity. Problems or mutations in a cell’s DNA are what causes cancer, and in this case, changes to developing blood cells in the bone marrow are what lead to the spread of hairy cells. What exactly causes the bone marrow to create these leukemia cells is still not well known. Some medical studies suggest that it may be a mutation of specific genes in our body.

Risk Factors of Hairy Cell Leukemia (HCL)

While men are at higher risk of getting HCL, there are other risk factors that can increase a person’s risk of getting HCL. These may include:

  • Radiation exposure with little to no protective equipment (inconclusive evidence, but a possible risk factor, nonetheless)
  • Long term exposure to heavy industrial chemicals from defoliants or pesticides
  • Long term exposure to organic solvents (i.e. benzene, used in making plastics)
  • Family history of HCL (genetics)

You must remember that having a risk factor does not mean you will contract the disease.

Diagnosing Hairy Cell Leukemia (HCL)

A thorough diagnosis is important in order to accurately determine if you or your loved one may have HCL. There are a number of tests that can be done, based on your medical history and by conducting a physical examination. Generally, the doctor will want to find out the following:

  • Past illnesses or injuries
  • Any family history of illnesses
  • Current medications taken
  • Any ongoing treatments
  • Any other complications

The physical exam will determine if you or your loved one may have an enlarged spleen or lymph nodes, or to find other irregularities. While an enlarged spleen is a general sign of HCL, blood tests are more accurate in detecting it, as a lower blood count in the absence of symptoms is a more common sign of HCL.

A complete, or full, blood count may be required to follow up on the initial investigations. This test measures the number of healthy blood cells in a sample of blood drawn from you or your loved one. Medical professionals may also perform a peripheral blood smear to look for hairy cells in the blood sample, as well as changes to the shape of blood cells.

There are other procedures that the doctor may perform.

Bone marrow testing

This diagnostic procedure takes a sample from your bone marrow for examination. There are two procedures involved: aspiration and biopsy. Bone marrow aspiration is when the doctor uses a needle to extract (or aspirate) a sample of cells from your bone marrow, while bone marrow biopsy extracts a small part of the bone marrow itself.

Samples are drawn from the hip bone, so the area will be numbed by the doctor before undertaking the test. This test will help doctors determine the state of the bone marrow and whether there are hairy cells present, and informs them of the right treatment plan for you.


This test uses special antibodies that will test the presence of specific leukemia cells, based on specific markers found on the surface of these cells. This will help identify specific types of leukemia, which again inform the possible treatment plan.

Flow cytometry

This is a laboratory test used to classify cells based on a number of characteristics, including their size, shape and any markers found on the cells’ surface.

CT scan

Also called CAT scans, this test requires an x-ray machine that scans and produces pictures of areas within your body for detailed examination. A dye may be injected into the bloodstream or consumed to allow internal organs to be visible. A CT scan may be done to check for swollen lymph nodes or an enlarged spleen or liver.

Staging of Hairy Cell Leukemia (HCL)

Staging is the process to determine how far cancer has progressed throughout the body. You will have encountered the term before if a loved one was previously diagnosed with cancer. Leukemia is a type of blood cancer, so there is also a need for a standard staging system.

In the case of HCL, however, there is no standard staging system. Some hospitals or medical bodies may consider HCL stages in terms of how many hairy cells are found in your body or the symptoms you experience from it. Based on the results from your diagnosis, doctors will determine the best course of action in treating HCL.

Treating Hairy Cell Leukemia (HCL)

Though HCL is not curable, treatment options allow you or your loved one to remove the leukemia cells in the body. Treatment will lead to remission, a partial or complete reduction of symptoms of HCL, which can last for many years. Usually, treatment does not need to start immediately if there are no symptoms, or if they are mild. This is called the “watch and wait” method. Follow-ups will be necessary to account for your/your loved one’s state of health; if there are noticeable changes (such as a drastic drop in blood count) in follow up reports, then treatment may begin.

There are instances where HCL may relapse, or reoccur, some time after remission. This may happen after years of being in remission, so even after treatment is complete, regular checkups are important in assessing your overall health during remission.


Chemotherapy involves the use of anti-cancer drugs to fight off HCL. This is the main treatment plan for HCL, and is highly effective in treating it; in some cases, 80 to 85 per cent of patients experience long-lasting and complete (no remainder of HCL in the body) remission.

There are two chemotherapy medicines commonly used:

  • Cladribine – given as either an injection just below the skin for 5 days in a row; or as a continuous drip directly into a vein for 7 days
  • Pentostatin – given by injection directly into a vein (intravenously) every 2 weeks until remission or the HCL is under control

Your blood count will also be monitored while undergoing chemotherapy, to ensure that it is taking effect on the leukemia cells.

While effective, you should always consult your doctor before undergoing chemotherapy. There are instances where individuals undergoing chemotherapy do not respond to treatment or may undergo significant side effects from the medication.

Some side effects that may occur include:

  • Increased infection risk
  • Fatigue
  • Nausea
  • High fever
  • Easily bruised, or bleeding

You should immediately report to a care provider if any of these side effects occur.


Immunotherapy sometimes referred to as biological treatments or targeted therapy, is a treatment that involves targeting differences in leukemia cells that enable them to thrive, and enabling the immune system to attack these leukemia cells. In some cases, immunotherapy involves both: a medicine is introduced to target the leukemia cells, allowing your immune system to identify and neutralize them. There are also medicines that help strengthen your immune system to ward off HCL.

For instances where chemotherapy is not effective against HCL, or if there is a relapse, immunotherapy may be recommended to treat the condition. You may even be prescribed an immunotherapy medicine to complement chemotherapy.

There are two types of medication used in immunotherapy.

  • Rituximab: attaches itself to proteins found on the surface of leukemia cells, allowing the immune system to target these cells and kill them
  • Interferon: a hormone that is naturally produced in the body to fight infections; it helps fight off leukemia cells and inhibit their growth while boosting the immune system; rarely used today, but maybe prescribed if required

There may also be side effects from the use of these medications. These may include fevers, chills, headaches or nausea. Again, report all side effects you experience to your care provider.


Surgical removal of the spleen, or splenectomy, is rare but may be done if:

  • The spleen is enlarged and causes pain or discomfort
  • It is destroying large numbers of healthy blood cells
  • The swelling has not reduced after chemotherapy

It will take time to recover from surgery, but in the event that HCL persists even after the splenectomy, your care provider may suggest further treatment until remission.

Clinical Trials

Clinical trials are often conducted by medical professionals to find new ways to safely and effectively treat HCL. Most existing treatment options were based on successful clinical trials. They are designed with scientific rigour and meet ethical standards to ensure scientific accuracy and safety are met throughout the trials. Even if a clinical trial does not meet expectations, the results may help to shine a light on important questions on the nature of HCL.

You or your loved one may opt-in to a clinical trial at any point of treatment. During the trial, there will be occasions where repeat tests will be conducted to determine how the treatment is going. Any decisions to proceed, delay or outright cancel the trial will be based on these results.

While there are ways to find ongoing clinical trials in the country, it is best to consult with a medical professional first before volunteering for any trials.

Treating Relapse/Refractory Incidences

There may be times when, sometime after remission, HCL will make a return or relapse. In other cases, the treatment may not have any effect on HCL at the start of treatment or during treatment. This is called refractory HCL.

Prior to deciding on re-treatment of relapses or refractory conditions, the medical team will need to correctly ascertain the cause of such a relapse/refractory condition. There may be instances where the blood count does not return to normal due to side effects caused by treatment.

For refractory cases, a different treatment plan may be necessary if there is no effect on the HCL, as it may have become resistant during the course of treatment. For example, if chemotherapy has no effect on your condition, you may be treated via immunotherapy instead.

For relapses, follow up tests will be conducted frequently (i.e. on a quarterly basis) to ensure that the condition has fully subsided, or if there may be trace amounts of HCL remaining. Generally, remission can last for many years before symptoms present themselves again. Should a relapse occur, another round of treatment will need to be undertaken to bring about another remission. The treatment plan will depend on the quality and duration of the first or preceding remission.

Living with Hairy Cell Leukemia (HCL)

It is always important to carefully consider your options before going for treatment. Research is important in helping you make informed decisions for care for yourself or your loved one. Speak to a healthcare professional who can assist you with answering your questions and addressing your concerns. It helps to have a list of questions to ask. Optionally, bring a chaperone along as well, as they may have their own set of questions they would like to ask.

HCL’s complications can make you or your loved one more vulnerable to illnesses. It is therefore recommended that you prioritise adequate care to ensure you or your loved one are well. This would include maintaining a healthy diet, exercising frequently, quitting unhealthy habits such as smoking, and so on. You may also consider getting a prescription for medicines that boost blood counts to abate the effects of anaemia.

It is also important to get sufficient support from loved ones. Talk with them about the condition and how you feel. It will help alleviate your stress and find solace in their warmth and understanding. You can also look to support groups with people who also have HCL to share experiences and find camaraderie. For example, the National Cancer Society Malaysia also provides support options and useful resources.

Because the diagnosis can be a stressful time, and subsequent treatment can produce a variety of side effects, you can consider investing time in various “alternative therapies”, such as art therapy, meditation and music therapy to help you or your loved one cope with the stress of the procedures. Constant communication is key to managing your overall health, as well, so let care providers know if you feel ill before, during or after treatment.

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About the Writer
Calvyn Ee
Calvyn is an aspiring author, poet and storyteller. He spends his time reading, gaming and building stories with his action figure photography.
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