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Find out about the grades and the difference between benign and malignant brain tumours.

Brain tumours are put into groups according to how quickly they are likely to grow. There are 4 groups, called grades 1 to 4.

To decide on the grade, an expert called a pathologist looks at a sample of the brain tumour.  They examine the cells under a microscope.

The more normal the cells look, the lower the grade. The more abnormal the cells look, the higher the grade.

Grade 1 and 2 tumours are low grade. Grade 3 and 4 tumours are high grade.

Benign or malignant

Doctors might refer to your low grade tumour as benign. Or your high grade tumour as malignant.

Benign tumours tend to be:

  • relatively slow growing 
  • less likely to come back after surgery if it is completely removed
  • less likely to spread to other parts of the brain or spinal cord 
  • less likely to need radiotherapy or chemotherapy after surgery 

Malignant tumours are more likely to:

  • be relatively faster growing 
  • come back after surgery, even if completely removed
  • spread to other parts of the brain and spinal cord 
  • need radiotherapy or chemotherapy to stop it coming back or to control symptoms 

With some types of cancer this black and white explanation of benign and malignant works well. With brain tumours, there are many grey areas.

For example, a slow growing benign tumour can cause serious symptoms and be life threatening if it's in an important part of the brain. Some low grade astrocytomas can spread to other parts of the brain or spinal cord. Radiotherapy and chemotherapy is sometimes used to treat benign tumours. 

So ask your specialist to explain what your grade means in your situation.

Changing from benign to malignant

Some benign tumours can develop into a malignant tumour. It is called malignant transformation or progression to malignancy.

For example, a grade 2 tumour could progress to a grade 3 tumour. Or a grade 3 tumour could change to a grade 4. 

Last reviewed: 
22 Sep 2015
  • Cancer and its Management (7th edition)
    Tobias J and Hochhauser D
    Blackwell, 2015

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