How is a brain tumour diagnosed?

Brain Tumours

How is a brain tumour diagnosed?

If your doctor (GP or A&E doctor) suspects you have a brain tumour, they will refer you to a specialist, such as a neurologist. These are specialists in brain and nerve disorders. If they suspect a child has a brain tumour, they will refer them to a paediatrician.

Neurological examination

If your doctor (GP or A&E doctor) suspects you have a brain tumour, they will refer you to a specialist, such as a neurologist. These are specialists in brain and nerve disorders. If they suspect a child has a brain tumour, they will refer them to a paediatrician.

The specialist will:

  • Ask questions about your health
  • Give you a physical examination

Test your nervous system (called a neurological examination) – this involves looking at your vision, hearing, alertness, muscle strength, co-ordination and reflexes.

They may also look at the back of your eyes to see if there is any swelling of the optic disc. Any swelling is a sign of raised pressure inside the skull, which could be a sign of a brain tumour.

Eye tests

If you have problems with your eyes or vision, you may visit your local optometrist for an eye test. Your GP may refer you to an optometrist to review your symptoms.

Most people should have their eyes examined every two years. You may be advised to have an exam more often depending on your age and eye health. Some people are entitled to a free NHS eye test.

If you experience problems with your eyes or notice changes, you should book an appointment with your optometrist.

Problems related to brain tumours may include:

  • abnormal eye movements
  • persistent/recurrent headache
  • suspected loss of vision
  • abnormal head position such as wry neck, head tilt or stiff neck
  • blurred or double vision and loss of vision.
  • Diagnostic brain scans

Scans provide a detailed 3D image of the brain by taking multiple pictures of the inside of your head. Scans are used during diagnosis. They allow doctors to see whether there is a tumour and, if there is, its size and position.

Scans are also used for monitoring during and after treatment.

The two scans that are most commonly used are:

  • CT scans
  • CT stands for Computerised Tomography. You may also sometimes hear doctors referring to CT scans as CAT scans – these are the same thing.
  • CT scanners use x-rays to build up the 3D image of the inside of your head. They take several cross-sectional pictures through your head, then use a computer to stack these 2D picture ‘slices’ into a 3D image.


A biopsy is where a sample of abnormal tissue is removed to help diagnose the type and grade of tumour you have. The sample is taken during an operation and examined under a microscope in a laboratory.

For brain tumours, sometimes a biopsy will be taken as part of a craniotomy. A craniotomy is an operation to remove all, or as much is safe, of your tumour.

However, depending on the location of your tumour, a craniotomy might not always be possible, so a smaller operation is performed to get a sample of the tumour for diagnosis.

This operation is a surgical biopsy and is often called a burr hole biopsy.The tumour sample will be sent to the laboratory to be analysed and diagnosed by a neuropathologist.

A biopsy generally takes about 1-2 hours and can often be done as a day case.The results of your biopsy will show the type and grade of your brain tumour. This will allow your healthcare team to decide the best treatment for you.

What happens during a biopsy?

First you will have an MRI scan or CT scan to show exactly where the tumour is.

The scan can be up to a few weeks before the biopsy operation.

You will then be given either a general anaesthetic to fall asleep.

Occasionally the procedure is performed under a local anaesthetic, but you will be sedated. If this is thought to be your best option, your healthcare team will discuss it with you, explaining what is done to prevent you feeling any pain, and help you mentally prepare for it.

Types of biopsy

Biopsy as part of a craniotomy – If you are able to have surgery to remove all or part of your tumour this is called a craniotomy. As part of this, your neurosurgeon may take a small sample of your tumour to send to the lab for testing.

Guided needle biopsy – During a guided biopsy your neurosurgeon uses either a CT or MRI scan to locate and take a sample from the tumour. This can be done in 2 ways:

Frame-based stereotactic biopsy – before your MRI or CT scan, you are fitted with a special frame around your head. Markers on the frame allow your surgeon to know exactly where to put the needle to remove a sample of the tumour.

Frameless neuronavigation biopsy – after an MRI or CT scan, your surgeon is able to use a neuronavigation system (computer-assisted technologies) to pinpoint precisely where the biopsy should be taken from. You will then be given a general anaesthetic to fall asleep and a very small ‘burr hole’ will be drilled into your skull by the neurosurgeon. A needle is passed through the hole to take a small sample of the tumour, which is sent to the lab for analysis and diagnosis.

Open neuronavigation biopsy – Sometimes a larger sample of the tumour might be needed, or if there is a high risk of bleeding, your surgeon may perform an open biopsy. This is for tumours which are on the surface of the brain, not deep inside. A neuronavigation system is used and a small part of your skull (‘bone flap’) is removed to give your neurosurgeon better access to your tumour. Samples are taken without passing a needle into the tumour. The hole is closed using staples or stitches.

After your biopsy, you may be given steroids to help with any brain swelling.

After a biopsy

After having a biopsy you may need to stay in hospital overnight or for a few days. However, sometimes a biopsy can be done as a day case and you will be allowed home that day.

If you have had a craniotomy, your recovery might take longer and you may need a longer stay in hospital.


A biomarker is a biological marker or indicator of a certain process happening in the body. If you have a brain tumour, a biomarker test may be used to look at the genes associated with your type of tumour.

With brain tumours, biomarker tests can be used to see if your tumour has certain changes in its genes that may be used to:

  • help diagnose the type of tumour you have
  • predict how fast your tumour will grow
  • suggest how you may respond to certain treatments, such as chemotherapy and, possibly, radiotherapy.

Research is still in early stages and it’s important to know that :

biomarkers are not treatments

biomarker tests are only available for certain types of tumours, but research is continually discovering more biomarkers

biomarkers often don’t give absolute answers, but suggest likely tumour behaviour

not all hospitals offer biomarker tests (although you may be able to be referred to another hospital that does)

there are advantages and disadvantages to testing.


Biomarker test results can be useful in giving more detailed information about your tumour type. This can help to give a more accurate diagnosis and plan appropriate, more personalised treatment.

For certain tumour types, they may also suggest how your tumour may respond to certain treatments and also give information that can help estimate your prognosis (likely outcome of your treatment).

The results may also help give an indication as to which clinical trials may be suitable for you. For more information about clinical trials, see our Clinical trials webpage and fact sheet.


While many scientists believe that biomarker testing is helpful, others argue that the results are sometimes unclear due to a number of factors. For example:

  • mistakes in detecting the marker
  • not enough of the tumour was available to test
  • the heterogeneity of the tumour.

Some people prefer not to know too much detail about their tumour and how this might predict their prognosis.

For example, if you have a biomarker test which suggests your tumour type doesn’t respond well to treatment, this is likely to be difficult news. If you’ve been working hard to maintain a positive frame of mind on a day-to-day basis, this could set you back.

Quite often biomarker testing is done routinely, so you may not be consulted before this is done. You can, of course, choose not to be told the result.

Ask your healthcare team if testing is done routinely and, if it’s not, think about it carefully and discuss it with them and your family before deciding whether to ask for it.

What is tumour heterogeneity?

Many tumours are heterogeneous. This means all the cells are not the same. Instead, some cells, or groups of cells, throughout the tumour will have different genetic mutations (changes in the genes) or a different molecular make-up.

If a sample is taken from a part of a tumour that’s different to the rest of the tumour, it may show different results to a sample taken from elsewhere in the same tumour.

This means that the results of the biomarker test may not truly reflect the tumour and its likely behaviour.

Things to be aware of about biomarkers for brain tumours

None of the predictions from biomarkers are perfect.

Some people’s tumours will respond differently to what the test predicts.

Biomarker testing isn’t suitable for everyone with a brain tumour and The Brain Tumour Charity is unable to advise on your individual case.

Biomarker tests can only be carried out on a sample of your tumour, either removed during a craniotomy or biopsy operation, and the sample has been analysed.

It doesn’t matter how long ago the biopsy was performed, so previous samples can be used, if they’ve been stored appropriately.

Testing for biomarkers is a relatively new practice, so it’s availability can vary widely, as the time taken to implement the new molecular tests will be different between centres.

How brain tumours are graded

Brain tumours are graded 1-4 according to their behaviour, such as the speed at which they are growing, and how likely they are to spread into other areas of the brain. Over time, some brain tumour’s behaviour can change and the tumour may become, or come back as, a higher grade tumour.

Each year in the UK, approximately 4,300 people are diagnosed with low grade, slow growing brain tumours and 5,000 with high grade fast growing brain tumours. Combined, this represents less than 2 out of every 10,000 people in the UK.

Brain tumours are graded from 1 – 4 depending on how they are likely to behave.

Grade 1 and 2 tumours (low grade)

Grade 3 and 4 tumours (high grade)

Confirming the diagnosis of the different grades of brain tumours is done, where possible, by analysing cells from the tumour, taken during a biopsy or during surgery. A neuropathologist examines the cells in the laboratory, looking for particular cell patterns that are characteristic of the different types and grade of brain tumour.

Why is the grade important?

Accurate diagnosis is important as it allows your medical team to give you information about how the tumour could behave in the future, and also to recommend treatment options. This could include a clinical trial.

Sometimes confirming the grade can be difficult as some low grade and high grade tumours can look very similar.

  • Low grade tumours
  • Low grade brain tumours are:
  • slow growing
  • relatively contained with well-defined edges
  • unlikely to spread to other parts of the brain
  • have less chance returning (if they can be completely removed).

Grade 1 and 2 tumours are low grade, slow growing, relatively contained and unlikely to spread to other parts of the brain. There is also less chance of them returning if they can be completely removed. They are sometimes still referred to as ‘benign’.

The term ‘benign’ is less used nowadays as this can be misleading. These low grade brain tumours can still be serious.

This is because the tumour can cause harm by pressing on and damaging nearby areas of the brain, due to the limited space capacity of the skull. They can also block the flow of the cerebrospinal fluid (CSF) that nourishes and protects the brain, causing a build-up of pressure on the brain.

High grade tumours

High grade brain tumours are:

  • fast growing
  • can be referred to as ‘malignant’ or ‘cancerous’ growths
  • more likely to spread to other parts of the brain
  • may come back, even if intensively treated.

Grade 3 and 4 tumours are high grade, fast growing and can be referred to as ‘malignant’ or ‘cancerous’ growths.

They are more likely to spread to other parts of the brain (and, rarely, the spinal cord) and may come back, even if intensively treated. They cannot usually be treated by surgery alone, but often require other treatments, such as radiotherapy and/or chemotherapy.

‘Mixed grade’ tumours

Some tumours contain a mixture of cells with different grades. The tumour is graded according to the highest grade of cell it contains, even if the majority of it is low grade.