Brain tumour

A guide for patients and carers

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Common questions about brain tumour

What is a tumour?

Our bodies are made from building blocks called cells each with its own structure and function. Cells grow and multiply naturally and normally as we grow up through childhood into adulthood and to repair tissue and wear-and-tear damage to our bodies (for example, when our skin heals after a cut or graze).

A tumour is a swelling or lump formed when certain cells grow and multiply abnormally.

What is a brain tumour?

A brain tumour is an abnormal growth of cells in the brain. If any brain cells grow and multiply abnormally to cause a brain tumour, this is called
a primary tumour.

If abnormal cells have spread to the brain from a cancerous tumour in another part of the body, this is called a secondary tumour or a metastasis ("secondaries" or metastases).

What are benign and malignant tumours?

Benign brain tumours are non-cancerous. They are always primary tumours (that is, they start in the brain). They do not spread into and invade the brain tissue surrounding them in the same way as malignant tumours (see below) and they do not send secondary tumours to other parts of the body. However, benign tumours can grow to a considerable size, creating pressure on and damaging the surrounding brain tissue.

Malignant brain tumours are cancerous. They spread into and invade the brain tissue surrounding them. The rate at which they invade the surrounding tissue depends on how malignant they are.

Primary malignant brain tumours very rarely spread from the brain to other parts of the body but they can cause problems by invading the cerebrospinal fluid (CSF) which surrounds the brain and spine. CSF flows
between four chambers in the brain (two lateral ventricles (cavities), the third ventricle and the fourth ventricle). Brain tumours can block the flow of CSF between these chambers and cause physical symptoms and other problems such as headaches.

Grading of brain tumours

Brain tumours are graded by doctors according to the speed at which they are growing. Slower growing tumours are given lower grades (grades 1 or 2) and faster-growing tumours are given higher grades (grades 3 or 4).

The grading system was devised by the World Health Organisation.

Metastases (secondary tumours)

The most common types of brain tumour are metastases or secondary tumours that have spread to the brain from malignant primary tumours in other parts of the body. Metastases are always malignant.

Malignant primary tumours in the lungs, breasts, skin (malignant melanomas) and bowel are the most common sources of metastases in the
brain.

Meningiomas

Meningiomas are intracranial tumours (tumours within the skull) found on the brain rather than in the brain. They are found on the meninges (the layers of membrane that surround the brain).

They are usually benign and can be managed effectively with surgery.

What causes brain tumours?

We do not yet know with any certainty what causes primary brain tumours and we do not know why some are benign and some are malignant.

Radiotherapy for childhood cancers and leukaemia has been identified as a risk factor and people who have undergone this treatment as children are at an increased risk of developing brain tumours as adults. However, the risk is low.

It used to be thought that some types of brain tumour occurred after head injuries but we now know that this is not the case except for a very small link between head injuries and some meningiomas.

Secondary brain tumours are always caused by a cancerous tumour in another part of the body.

There have been concerns that the use of mobile phones is a risk factor for developing brain tumours. Currently, the scientific evidence that we have available suggests that this is not the case. However, because the widespread use of mobile phones is still relatively recent, there has not been extensive research into any possible health risks. Studies into the use of mobile phones have begun but it might be many years before any possible links to brain tumours are established.

Could I have prevented it?

No. We have not established clear risk factors for the majority of brain tumours in the way that, for instance, smoking has been established as a clear risk factor for lung cancer.

Are there warning signs?

No, there are no warning signs before the onset of symptoms. Some benign tumours grow very slowly over several years and can reach a large size before they are detected. Malignant tumours tend to grow more quickly and will usually have been present for a shorter time when they are discovered.

The onset of symptoms does not tell us how long the tumour has been there or whether it is benign or malignant.

Why me?

We do not know why the majority of brain tumours happen and, in most cases, there is no way of identifying the people who are at risk. There is a slight hereditary factor. A very small number of people can inherit from their family a greater risk of having a brain tumour.

Are my family at risk?

The hereditary risk of brain tumours is very low. It is extremely rare for a brain tumour to be traced to a genetic factor passed on within a family. If one of your relatives has also had a brain tumour it can almost certainly be put down to coincidence.

There are some very rare family cancer syndromes which affect the genes that control the multiplication of cells and can increase the risk of brain tumours. An example is Li-Fraumeni syndrome.

How common are brain tumours?

Approximately 5000 people are diagnosed with a primary brain tumour each year in the UK. Slightly less than one third of these tumours are benign. The rest are malignant.

Primary brain tumours can affect people of any age. They are more common in people aged between 50 and 70 years but are also the most common cancer after leukaemia to affect children.

In addition, around a quarter of people who have or have had cancer in a different part of their body develop secondary brain tumours (metastases). Approximately 7500 people are diagnosed with secondary brain tumours each year in the UK.

Please note that, currently, the number of people diagnosed with brain tumours in the UK is not systematically recorded for all types of tumour. The above numbers are approximate and they are conservative estimations.

What other terms are used to describe brain tumours?

Lots of different terms are used to describe brain tumours. They include swelling (the word tumour literally means ‘a swelling’), growth (because tumours form when cells grow abnormally) and lesion or space-occupying lesion (SOL). Space-occupying lesion is a term used when the medical team are not yet sure whether the abnormal area seen on a brain scan is a tumour or another problem such as an abscess, inflammation, or bleeding (haemorrhage) in the brain. This is often the situation after a scan has been done but before the results of a biopsy are known.

Doctors might use swelling, growth or space-occupying lesion when they do not yet know what type of tumour is involved.

The term cancer is sometimes used to describe malignant brain tumours but this term is usually reserved for describing malignant tumours elsewhere in the body.

If you are confused by any of the terms used by your doctors, you should ask them to explain. They are not deliberately trying to baffle you. Sometimes doctors forget how confusing these different terms can be.

Names of brain tumours

There are many different types of brain tumour, some of which have long and complicated medical names.

The names of specific brain tumours tend to be based on the type of cell that is growing abnormally or their particular location in the brain. For example, gliomas grow from glial cells and, more specifically, astrocytic gliomas grow from a particular type of glial cell called astrocytes (‘star-shaped’ cells).

An example of tumours named after their location in the brain is pituitary tumours such as pituitary adenomas which grow in the pituitary gland.