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Hairy cell leukaemia (HCL) is a very rare form of cancer. It usually develops very slowly and is referred to as a chronic leukaemia.
Blood cells are formed in the bone marrow, which is the spongy tissue found inside the bones. Blood-forming stem cells divide to produce either more stem cells or immature cells that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. Hairy cell leukaemia (HCL) is a specific type of leukaemia in which the lymphocytic (antibody producing) white blood cells that are produced by the bone marrow are affected.
A lymphoid stem cell becomes a lymphoblast cell and then one of three types of lymphocytes (white blood cells):
In HCL there is an excess number of lymphocytes in the circulating blood. These lymphocytes are abnormal and cannot help the body to defend against infections. They are called hairy cells because the cells have fine projections on the surface – which look like hairs under the microscope. When you have HCL, the marrow is not able to make enough normal blood cells.
HCL is very similar to a type of leukaemia called chronic lymphocytic leukaemia (CLL).
The cause of HCL is not known. The only factors which are definitely known to increase the chance of developing the condition are older age and being male. You cannot catch HCL from someone who has it and you cannot pass HCL on to your children.
What are hairy cells?
The normal equivalent of the hairy cell is a type of white blood cell called a B lymphocyte. The function of a B lymphocyte is to produce antibodies which help the body to defend itself against infection. A very important recent discovery has been the fact that a very high proportion, possibly all, hairy cells have a specific mutation of a gene called BRAF. This is not an abnormality which has been passed on by parents; the gene is only abnormal in your hairy cells and not in your normal cells. This may help in confirming diagnosis of HCL and in developing new treatments.
About a quarter of all patients have no symptoms at the time of diagnosis. Typically these patients are identified because of abnormal results from a routine full blood count.
Symptoms can include:
If you are experiencing any of the symptoms above, you should visit your doctor. A blood test will be arranged and if the results show HCL, you will be referred to a haematologist. They will take your full medical history, carry out a physical examination and initiate further blood tests.
The blood tests will show the number of abnormal white blood cells, and the typical appearance of ‘hairy’ cells may also be seen in the blood sample. People with HCL may also have low numbers of platelets and red blood cells. Other blood tests are usually done to check your general health.
The spleen becomes enlarged in most people with HCL. Your specialist will usually be able to feel this when examining you.
A bone marrow biopsy may also be taken from the hip to confirm diagnosis.
If you are being treated for any type of leukaemia, you may be asked to consider taking part in a clinical trial. Clinical trials are scientific studies to find the best treatment; you can find more information on our website here.
The aim of treatment is to reduce the number of abnormal cells to as low as possible. It is generally accepted that standard treatment will not cure HCL; but it does offer a very high chance of a normal lifespan with a good quality of life.
Treatment options include:
Watch and wait
If you have no symptoms when you are first diagnosed with HCL and your blood counts are not very low, your haematologist may suggest a ‘watch and wait’ approach. This usually involves regular check-ups and blood counts, as well as your haematologist advising you on ways to live a healthy lifestyle. If symptoms develop or the disease progresses, you may then start a suitable treatment.
Chemotherapy has a very high success rate in the treatment of HCL.
It does not cure the disease but it gives very good control and most patients can expect a normal or near-normal lifespan.
The main drugs used are pentostatin (2-deoxycoformycin or DCF) and cladribine (2-chlorodeoxyadenosine or CDA) which are purine analogues.
Rituximab is a monoclonal antibody which has been used widely to treat a condition called CLL and which may be useful if HCL comes back (relapses) after responding to treatment.
Splenectomy (surgical removal of the spleen)
This was a standard treatment for HCL before effective drugs became available. It may be an option if your enlarged spleen is painful and causing complications and your blood count results are reasonably normal. If you have a splenectomy, it may take some time for it to improve your condition, so it is recommended that you do not have any treatment for at least six months.
Interferons are proteins that occur naturally in our bodies and help us fight infection. Interferon alpha can be used to treat HCL – usually only in cases where the numbers of normal blood cells are very low and a very quick response is needed. Once the blood count has improved, interferon can be stopped and treatment with cladribine or pentostatin given instead. Interferon is very rarely used nowadays.
We understand going through a blood cancer journey can be difficult. It may help to talk to a close friend or relative about how you are feeling. Here are some questions that may be useful to ask your doctor.