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Hairy cell leukaemia variant (HCL-V)

Hairy cell leukaemia variant (HCL-V) is a separate type of leukaemia from the typical or classic hairy cell leukaemia.

What is it?

Doctors used to think HCL-V was a rare type of hairy cell leukaemia, but they now consider it to be a completely different condition. HCL-V and classic hairy cell leukaemia are both chronic leukaemias and they develop slowly from cells called B lymphocytes. 

B lymphocytes are a type of white blood cell that fights infection. When you have hairy cell leukaemia, the body makes too many B lymphocytes. These B cells aren’t normal and can’t fight infections properly. If you look at the cells under a microscope you can see tiny, hair-like, outgrowths on their surface.

HCL-V cells:

  • are usually smaller than classic hairy leukaemia cells
  • have different genetic material in the cells
  • respond differently to treatment

HCL-V is less common than classic hairy cell leukaemia. It can develop at any age, but it is more common in older people.

Knowing the type of leukaemia you have helps your doctor to decide the best treatment for you.


The symptoms of HCL-V are the same as for classic hairy cell leukaemia. They include:

  • a swollen tummy (abdomen) due to a bigger (enlarged) spleen
  • frequent infections
  • tiredness and breathlessness due to low levels of red blood cells (anaemia)
  • bleeding and bruising due to low levels of platelets (platelets are important for blood clotting)


Your doctor will examine you and arrange blood tests to check your general health. Other tests include:

  • bone marrow tests
  • an ultrasound scan or a CT scan

The blood tests show how many blood cells you have and whether they are normal. Tests usually show a high white blood cell count.

You also have tests to look at the bone marrow cells. The bone marrow tests can show whether you have HCL-V or classic hairy cell leukaemia.

You might have tests to look for anything unusual in the chromosomes of the leukaemia cells. Chromosomes contain the genetic material inside cells. These tests are called cytogenetics (pronounced sigh-toe gen-et-ics).

The ultrasound scan or CT scan will show whether your spleen is enlarged and if you have any swollen lymph nodes.

Treatment decisions

If you don't have any symptoms you probably won’t need to start treatment immediately. Some people don’t need to start treatment for a number of years. Instead you have regular check-ups. Doctors call this watch and wait.

You have treatment if your blood cell levels change or if you develop symptoms. Your treatment will depend upon:

  • how far your leukaemia has developed
  • your symptoms
  • your general health and level of fitness

Doctors are still trying to find the best treatments for HCL-V.

If your leukaemia starts to cause uncomfortable symptoms you may have surgery to remove your spleen.

You might have a targeted drug (such as rituximab) if you can’t have surgery, or you get symptoms after surgery. You might have this in combination with chemotherapy. 



Many people with HCL-V have an enlarged spleen. The spleen filters the blood and breaks down worn out red blood cells. It also gets rid of bacteria and dead tissue. In HCL-V the spleen can get so clogged up with cells it can’t work properly.

Your doctor might suggest removing your spleen if:

  • the spleen is so large that it is causing pain
  • it is destroying too many red blood cells or platelets

Removing the spleen (splenectomy) can help to control symptoms.

Targeted cancer drugs

Targeted cancer drugs work by targeting the differences in cancer cells that help them to grow and survive.

Rituximab is a type of targeted drug called a monoclonal antibody. It works by searching for a protein that is found on normal and leukaemic white blood cells (lymphocytes). Rituximab sticks to the protein on the cells. The immune system can then target the cells and kill them.

Sometimes, rituximab or a similar drug is combined with chemotherapy.


Chemotherapy means using anti cancer drugs to destroy cancer cells.

You might have a chemotherapy drug called cladribine.

If hairy cell leukaemia variant comes back

Treatment for HCL-V aims to control the cancer for as long as possible. This is called remission. 

If your HCL-V comes back (relapses) after targeted drugs or chemotherapy, you will have more treatment. Treatment depends on:

  • the treatment you had before 
  • the time since your last treatment 
  • your general health and fitness 

If your first treatment doesn't put HCL-V into remission, you might have a different targeted drug. This might be part of a clinical trial. 

Very rarely, doctors might recommend you have high dose chemotherapy with a stem cell transplant. This is not suitable for everyone because it is a very intense treatment. You can only usually have it if you are in reasonably good health.

Newer treatments

Researchers are looking at other targeted drugs for hairy cell leukaemia. 


This is a type of monoclonal antibody. Alemtuzumab targets a protein called CD52. It sticks to all the CD52 proteins it finds on the leukaemia cells. Then the immune system picks out those cells and kills them.


These are monoclonal antibodies that have a toxin (type of poison) attached to them. The antibody attaches to a protein on the leukaemia cells and delivers the toxin. The toxin kills the cancer cells. 

These treatments have only been tested in a few people, so it is too early to know how well it works. More research is needed to look at the benefits and possible side effects.

Research and clinical trials

There may be fewer clinical trials for rare types of cancer than for more common types.

It is hard to organise and run trials for rare cancers. Getting enough patients is critical to the success of a trial. The results won't be strong enough to prove that one type of treatment is better than another if the trial is too small.

The International Rare Cancers Initiative (IRCI) aims to develop more research into new treatments for rare cancers. They are designing trials that involve several countries so that more people will be available to enter trials.

Coping with hairy cell leukaemia variant

Coping with a rare condition can be difficult, both practically and emotionally. Being well informed about your condition and its treatment can help you to make decisions and cope with what happens.

The symptoms of HCL-V often mean that you find it hard to do everyday things. Talk to your doctor or nurse about any symptoms you have. There may be supportive treatments that can help you. You may also feel better if you:

  • eat a healthy well balanced diet
  • do some exercise – after checking with your doctor
  • rest when you are tired

If you get tired easily, try to work out your priorities each day. Talk to your family and friends and ask for any help you need. 

Last reviewed: 
23 Nov 2020
Next review due: 
23 Nov 2023
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