Blood cells are formed in the bone marrow, which is spongy tissue found inside 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.
A myeloid stem cell becomes one of three types of mature blood cells:
- Red blood cells that carry oxygen to all tissues of the body.
- Platelets that form blood clots to stop bleeding.
- Granulocytes (white blood cells) that fight infection and disease.
A lymphoid stem cell becomes a lymphoblast cell and then one of three types of lymphocytes (white blood cells):
- B lymphocytes that make antibodies to help fight infection.
- T lymphocytes that help B lymphocytes make the antibodies that help fight infection.
- Natural killer cells that attack cancer cells and viruses.
Prolymphocytic leukaemia (PLL) affects B lymphocytes in about four out of five case. About one in five cases of PLL affects T lymphocytes. The cells seen in the blood are large immature lymphocytes called prolymphocytes.
PLL is similar to CLL but affects a more immature cell type.
What causes PLL?
In most cases of PLL there is no obvious cause but it is important to understand that:
- It is not a condition which can be caught from someone else (contagious)
- It is not passed on from a parent to a child (inherited)
- Age – Like most forms of cancer PLL is more common in older people
- Being male – PLL affects slightly more males more than females
- CLL – A small proportion of cases of B-PLL affects people who have already been diagnosed with CLL.
Signs and symptoms of PLL
Most people with PLL have an enlarged spleen at the time when they are diagnosed. It is unusual for the lymph nodes (glands) to be enlarged. Lymph nodes are more likely to be enlarged in T-PLL than in B-PLL. In T-PLL there may be leukaemia cells in the skin.
There are no specific signs or symptoms which would allow a diagnosis of PLL to be made. The most common signs and symptoms are caused by the bone marrow being unable to produce enough normal blood cells.
- Anaemia – due to lack of red blood cells.
- Weakness, tiredness, shortness of breath, light-headedness, palpitations
- Infections – due to lack of normal white blood cells.
- Infections are more frequent, more severe and last longer.
- Fever, malaise (general feeling of illness) and sweats.
- Purpura (small bruises in skin), nosebleeds, bleeding gums.
- Bleeding and bruising – due to lack of platelets.
Patients with PLL often have a very high white cell count at diagnosis. There is a condition called mixed CLL/PLL in which there are prolymphocytes present but these make up less than half of the lymphocytes in the blood. PLL is diagnosed when more than half of the lymphoid cells in the blood are prolymphocytes. Specialised tests are needed to distinguish between B-PLL and T-PLL.
Most patients with PLL will have bone marrow samples taken to confirm the diagnosis and to help to determine exactly what type of leukaemia a patient has. A bone marrow sample may not be necessary if treatment is not being started, but it is often valuable to have an initial sample to compare with later samples. More specialised tests are often done at the same time.
Blood samples will be taken to test for any problems with the liver, kidneys or other organs. Some blood tests and scans will be repeated to check for the response to treatment and any complications. Other tests are usually only done at diagnosis.
Blood tests and bone marrow samples may be repeated during treatment to monitor response.
Treatment of PLL
Some patients with PLL do not need to start treatment immediately after diagnosis. If patients are not being treated they have regular check-ups. This is known as “watchful waiting” or “active monitoring”. Treatment is started when there is evidence of progression or when symptoms are causing distress.
PLL is not considered curable with standard treatments; with the possible exception of stem cell transplants in a small number of younger and/or fitter patients.
The main ways in which PLL is treated are:
- Chemotherapy – Cell-killing drugs
- Biological therapy – Treatments which use the immune system to destroy leukaemia cells. Often these use antibodies against markers on the PLL cells – these are known as monoclonal antibodies
- Radiation therapy – Sometimes given locally to relieve symptoms caused by swollen spleen
- Stem cell transplant – A small minority of younger/fitter patients may be given a stem cell transplant (bone marrow transplant). This is done using healthy stem cells from a donor
Chemotherapy is the use of cell-killing drugs. These kill the cancer cells and/or stop them from dividing. Chemotherapy is usually given in blocks or ‘cycles’ of treatment. One cycle of treatment will consist of a series of doses of chemotherapy followed by a break for the healthy cells to recover.
Chemotherapy is normally given as a combination of drugs. The details of your treatment will vary depending on the type of PLL, age and general fitness. Patients will be given a chance to discuss treatment options and detailed information on the treatment plan before it starts. The side effects of treatment vary between different types of treatment and different patients.
Patients will be given detailed information about any likely side effects before you start treatment.
Questions to ask your medical team about PLL
We understand going through a blood cancer through 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.
- How would I know if I had PLL?
- What tests will I need to have?
- What will the tests show?
- How long will the results take?
- How rare is PLL?
- What sort of treatment will I need?
- How long will my treatment last?
- What will the side effects be?
- Is there anything I should or shouldn’t eat?
- Will I be able to go back to work?
- Where can I get help with claiming benefits and grants?
- Where can I get help dealing with my feelings?
We have free patient information available for PLL patients.
You can download the booklets on our information pages here.
Alternatively, you can have the information delivered free of charge by requesting it through our resources page.
Published date: August 2016
Review date: August 2018