Grades of brain tumours

Doctors put brain tumours into groups according to how quickly they are likely to grow. These are called grades.

The grade of a brain tumour gives doctors an idea of how the tumour might behave.

What is the grade of a tumour?

Grading is a way of dividing tumour cells into groups.

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. This might be after your:

• biopsy
• surgery to remove some, or all, of the tumour

The pathologist bases the grade on how the cells look. They also look at genes and proteins in the tumour cells.

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

Generally, Grade 1 and 2 tumours are low grade. Grade 3 and 4 tumours are high grade. The high grades are a form of cancer.

The grading system differs, depending on the type of brain tumour you have. For example, all oligodendrogliomas are either grade 2 or grade 3. And meningiomas range from grades 1 to 3. 

Your doctor or nurse can tell you more about the grade of your tumour and what this means.

Grade 1

The cells look very like normal cells. They are usually slow growing and less likely to spread. 

Grade 2

The cells look less like normal cells. They are usually slow growing but can grow into the nearby brain tissue. Doctors sometimes call grade 2 gliomas 'diffuse brain tumours'.

Grade 3

The cells look more abnormal. They can spread to other parts of the brain and the spinal cord. Doctors sometimes call grade 3 gliomas 'anaplastic tumours'.  These tumours are cancerous (malignant).

Grade 4

The cells look very abnormal. These are the fastest growing tumours and they often come back after treatment. They can spread to other parts of the brain and sometimes the spinal cord.

These tumours are cancerous (malignant).

Benign or malignant?

Doctors might refer to some low grade tumours as non cancerous (benign). And high grade tumours as cancerous (malignant).

This grading system generally works well for most tumours. But for some brain tumours, it isn’t as clear as this.

For example, a slow growing benign tumour can cause serious symptoms and be life threatening if it's in a particular part of the brain. And sometimes a low grade brain tumour can change over time and become high grade.

Benign tumours are sometimes treated with radiotherapy and chemotherapy. This is to help to control them and reduce the risk of tumour coming back.   

Changing from benign to malignant

Some low grade tumours develop into malignant tumours. This is called malignant transformation or disease progression.

For example, a grade 2 tumour could progress to a grade 3 tumour. Or a grade 3 tumour (for example, an astrocytoma) could change to a grade 4. 

Other tests on the cells

Your doctor also looks to see if there are certain gene  changes in the cells of some types of brain tumours. These tests are also called biomarker or molecular studies.  

This can help the doctors grade your brain tumour. It also helps your doctor:

• understand the type of brain tumour you have
• work out how quickly it might grow or re-grow in the future
• make decisions about treatment
• work out how likely it will respond to treatment

Doctors in the laboratory measure the level of certain biomarkers. There are a number of different biomarkers.