Grades of brain tumours

What is the grade of a tumour?

Grading is a way of dividing tumour cells into groups.

To work out 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 much 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. They may come back after treatment. Sometimes they can develop into a higher grade tumour.

Grade 3

The tumour cells look more abnormal. They can spread to other parts of the brain and the spinal cord. These tumours are cancerous (malignant).

Grade 4

The tumour cells look very abnormal. These tumours grow quickly and 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 may be life threatening if it's in a particular part of the brain. 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 the tumour coming back.   

We have information about astrocytomas and other common types of brain tumours

Changing from benign to malignant

Some low grade tumours develop into high grade (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 tumour.

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.  

These tests can help 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 come back

• decide on the best treatment

• work out how likely it will respond to treatment

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

Read more about the biomarker tests on our page about the types of brain tumours