What is a brain tumour?

A brain tumour is a lump in the brain which is caused when brain cells divide and grow in an uncontrolled way. What causes brain cells to start growing and dividing differently from healthy cells, forming a high grade (cancerous) or low grade (benign) tumour is not yet understood.

There are over 130 different primary brain and spinal tumours which are grouped and named according to the type of cell they grow from, their location in the brain and how quickly they are likely to grow and spread.

Primary brain tumour

A brain tumour originating in the brain is known as a primary brain tumour.

Secondary brain tumour

If the tumour started somewhere else in the body e.g. the lung, then spread to the brain, it is known as a secondary brain tumour or metastases. There are over 130 different primary brain and spinal tumours which are grouped and named according to the type of cell they grow from, their location in the brain and how quickly they are likely to grow and spread.

How common are brain tumours?

Around 11,000 people are diagnosed with a primary brain tumour each year. This means that 29 people in the UK are diagnosed with a brain tumour every day. It is important to note that other conditions can cause similar signs or symptoms of brain tumours, but it is important to recognise these, so you can go to your doctor if you are concerned.

How brain tumours form

Normal cell division and growth

The images below show normal cell division and growth and what happens when there is abnormal cell division and growth, which can lead to the development of a tumour.

Signals from your genes tell your cells when to grow and when to stop growing, when to divide and when to die. This means your cells normally grow in a controlled way.

If these signals are not there, our bodies have further checkpoints to stop cells dividing in an uncontrolled way.

When a cell divides, it has to copy its genes to put into the new cell. However, mistakes can sometimes be made when copying the genes. These mistakes are called mutations.

graphic showing how normal cells divide

Abnormal cell division and growth, leading to the development of a tumour

Many mutations don't have any obvious effect, but if a mistake happens in a gene that helps to control how a cell grows and divides, it can cause the cell to grow uncontrollably and a tumour to grow.

This could be by either making the cell think it is receiving a growth signal even when it's not, or by shutting down the checkpoints that would normally stop the cell from dividing. As a result, the cell continues to divide.

Each of the new cells formed will also have this change (mistake) in the gene and so will also keep dividing when it shouldn't. As a result, more and more cells keep dividing and develop into a tumour.

a graphic diagram showing the process of cancer cell division

It's important to know that these types of mutation are mistakes that are found only in the tumour cells and not in the egg or sperm cells that make up a baby. This means they will not be inherited by your children.

Very often, we don't know what will have caused your brain tumour, read more about the brain tumour risk factors we know about.

Research, including pioneering programmes funded by The Brain Tumour Charity, is gradually discovering which genes are involved in causing different types of brain tumour to develop in the first place, as well as their ongoing growth.

This will hopefully lead to discovering what causes the mistakes in the genes to happen and also to treatments that are tailored to the genetic make-up of each person's tumour.

Read more about brain cells and brain tumours.

Find out more

Whether you've been diagnosed with a brain tumour, or it's a family member or friend, find out more about the types of brain tumour, how they are diagnosed and treated.

Diagnosing brain tumours

Read about how brain tumours are diagnosed, brain tumour grading (1-4), scans for both adults and children, and prognosis.

Types of brain tumour

There are over 130 types of brain tumour but in this page you will find detailed, reliable information the most common types.

Treating brain tumours

Read about different treatment options that may be available to you. Including neurosurgery, chemotherapy and radiotherapy.

If you have further questions, need to clarify any of the information on this page, or want to find out more about research and clinical trials, please contact our team:

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