Primary central nervous system lymphoma (PCNSL)

Primary central nervous system lymphoma (PCNSL) is a type of blood cancer that affects the brain, spinal cord or eyes (the central nervous system).

PCNSL is a type of non-Hodgkin lymphoma. It affects white blood cells called B cells, causing them to grow out of control.

Other types of lymphoma can spread to the brain or spine from other areas of the body. This is called secondary CNS lymphoma. PCNSL starts in the central nervous system and does not affect the rest of the body.

PCNSL can affect parts of the eye. In this case, doctors count the eye as part of the central nervous system. Sometimes the eye is the only area affected by PCNSL.

In most cases, PCNSL is a variation of a more common blood cancer called diffuse large B-cell lymphoma (DLBCL). Because of where it starts, PCNSL affects the body differently, and is not treated in the same way as DLBCL.

PCNSL is a fast growing blood cancer. Treatment usually starts within a few weeks of diagnosis.

Thanks to research, treatment for PCNSL has improved in recent years. Most people go into remission, where there are few or no lymphoma cells left, after treatment.

Your individual prognosis will depend on things that are personal to you, such as your age, your overall health and where the lymphoma is in your body. It also depends on how well the first treatment works, but there are more treatment options if it doesn’t work as well as hoped.

PCNSL can cause a wide range of symptoms, depending on where it grows. Common symptoms include:

• changes in behaviour or memory (forgetfulness, confusion, mood swings)
• trouble speaking or understanding
• weakness on one side of the body
• eye pain or problems with your eyesight
• headaches, feeling or being sick
• seizures (fits)
• depression or personality changes.

To get an accurate diagnosis, doctors will run a range of tests. You may have:

Scans

• an MRI scan of your brain and spine to check where the lymphoma cells are
• a PET-CT scan to check other areas of your body
• if you have testicles, an ultrasound to rule out testicular lymphoma.

Tissue or fluid tests

• a biopsy – a sample of tissue taken from your brain under anaesthetic, so you won’t feel anything
• a biopsy or sample of fluid taken from your eye, under anaesthetic
• a lumbar puncture (sometimes known as a spinal tap) to take a sample of spinal fluid. This is usually only done if a biopsy isn’t possible.

Tissue or fluid samples are sent to a lab to check for lymphoma cells. Doctors may also check for particular genetic changes that show you have lymphoma.

Blood tests

You may have blood tests to check how well your liver and kidneys are working and count the number of each type of blood cell in your blood (a full blood count).

We have more information on common tests for blood cancer, including scans.

Other tests

You may have a range of neurological tests to find out whether the lymphoma has affected your memory, thinking skills and movement. These tests may be repeated after treatment.

Your treatment will depend on your overall health and fitness, and how the lymphoma reacts to the first round. These are the main treatment options:

If your hospital team think that standard treatments will be hard for your body to cope with, you may be offered one or more of these treatments:

• less intensive chemotherapy
• lower dose radiotherapy
• steroids
• a combination of these.

These treatments aim to control the lymphoma and ease your symptoms.

If the lymphoma only affects the eyes and you are fit enough, you are likely to have the same treatment as for other types of PCNSL.

Less fit people may have chemotherapy injected directly into the eye – you’ll have drops to numb your eye, so this won’t hurt.

You may be offered treatment through a clinical trial. A clinical trial will give you the best treatment currently available on the NHS, and the chance of a newer treatment that may be even better.

It's your choice whether you go on a clinical trial and you can withdraw at any time.

Side effects are unwanted effects of treatment. They depend on the treatment you are having and vary from person to person – ask your hospital team what to look out for.

You won’t have all of the possible side effects and there are things you and your hospital team can do to help. Tell them if you notice anything new or different during your treatment.

We have more information on common side effects of blood cancer treatment.

Supportive care

Supportive care doesn’t aim to kill lymphoma cells but helps your body cope with your any symptoms and side effects. This could include medicine to protect you against infections.

Read more about your infection risk as someone with blood cancer.

If PCNSL comes back (relapses), you may have the same combination of chemotherapy drugs, or a different combination, depending on how long it has been since your last treatment.

You may be offered a stem cell transplant or whole brain radiotherapy if you have not had it before.

There is lots of research happening to find new targeted treatments for PCNSL and other blood cancers. You may be offered one of these treatments through a clinical trial.

You are likely to have MRI scans during and after your treatment, to check what’s happened to the lymphoma. Your doctor might suggest follow-up scans every 3 to 4 months for the first 2 years after treatment. Ask your hospital team about your follow-up plan.

You may need assessment and support from other medical professionals, including:

• a neurologist or neuropsychologist for memory and other cognitive difficulties
• a physiotherapist for movement or co-ordination problems.

If treatment doesn’t clear the lymphoma, you may see a palliative care team. Palliative care aims to manage your symptoms and give you the best possible quality of life.

A blood cancer diagnosis can affect your life in many ways: your mental health, your financial situation, the effect on your family and friends.

You may find it helpful to read our information on these topics:

• mind and emotions, including self-help tips and accessing counselling
• money, work and other practical advice
• guidance on eating well with blood cancer
• the benefits of keeping active
• information for family and friends.

Call our Support Line nurses free on 0808 2080 888 to talk through anything that’s worrying you or you’re not sure about.

First published August 2025. Next full review due August 2028. We may make factual updates to the information between reviews.

We would like to thank Consultant Haematologist Dr Matthew Wilson for checking the clinical accuracy of this information.