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Types of primary brain tumours

There are about 130 different types of brain tumour. They are generally named after the type of cell they develop from. Most develop from the cells that support the nerve cells of the brain. These are called glial cells. A tumour of the glial cells is called a glioma. Brain tumours can also be named after the area of the brain they are growing in. There is information below about some of the most common types.

Grade – benign or malignant

Brain tumours are put into groups according to how quickly they are likely to grow. A pathologist examines the tumour cells under a microscope. The more abnormal the cells look, the more quickly the tumour is likely to grow and the higher the grade. As a rule of thumb, low grade tumours are regarded as benign and high grade as malignant.

By benign we generally mean that the tumour is relatively slow growing. It is less likely to come back after it is completely removed and is less likely to spread. It may not need treatment with chemotherapy or radiotherapy after surgery.

By malignant we generally mean that the tumour is relatively fast growing. It is likely to come back after surgery, even if it is completely removed. It may spread to other parts of the brain or spinal cord. After surgery it will need radiotherapy or chemotherapy to try and stop it coming back.

Changing from benign to malignant

In some patients, a benign tumour will develop into a malignant tumour but this is not common. It is called malignant transformation or progression to malignancy.

 

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Sorting brain tumours into different types

There are about 130 different types of brain tumours. They are generally named after the type of cell they developed from. Most brain tumours develop from the cells that support the nerve cells of the brain called glial cells. A tumour of glial cells is a glioma.

Brain tumours can also be named after the area of the brain they are growing in. A tumour of the pituitary gland is called a pituitary adenoma. A tumour developed from the covering of the brain (the meninges) is called a meningioma. Tumours growing from the nerves entering the brain are called neuromas. An acoustic neuroma is a tumour growing on the nerve that controls hearing.

 

Brain tumour grade – benign or malignant

Brain tumours are put into groups according to how quickly they are likely to grow. There are 4 groups, called grades 1 to 4. A pathologist examines the cells under a microscope. The more normal the cells look, the more slowly the brain tumour is likely to develop and the lower the grade. The more abnormal the cells look, the more quickly the brain tumour is likely to grow and the higher the grade. Low grade gliomas (grade 1 and grade 2) are the slowest growing brain tumours.

You may have been told you have a benign tumour or a malignant tumour. As a rule of thumb, low grade tumours are regarded as benign and high grade as malignant. By benign, we generally mean the following.

  • The tumour is relatively slow growing
  • It is less likely to come back if it is completely removed
  • It is not likely to spread to other parts of the brain or spinal cord
  • It may just need surgery and not radiotherapy or chemotherapy as well

By malignant, we generally mean the following.

  • The tumour is relatively fast growing
  • It is likely to come back after surgery, even if completely removed
  • It may spread to other parts of the brain or spinal cord
  • It can't just be treated with surgery and will need radiotherapy or chemotherapy to try to stop it from coming back

With other types of cancer, these black and white explanations of benign and malignant often work well. But with brain tumours, there are a lot of grey areas. Some low grade astrocytomas can spread to other parts of the brain or spinal cord. Radiotherapy and chemotherapy are sometimes used to treat benign tumours. Even a slow growing tumour can cause serious symptoms and be life threatening if it is in an important part of the brain. So, it is important to ask your specialist to explain your own situation to you fully and simply.

 

Changing from benign to malignant

In some patients, a benign tumour will develop into a malignant tumour but this is not common. It is called malignant transformation or progression to malignancy.

 

Gliomas

Around 45 out of 100 (45%) of all primary brain tumours are gliomas. There are 3 main types of glioma

A fourth type is called unspecified glioma, which is where the type is not clear or there is a mixture of cell types.

Your doctor will use the grade of your glioma to decide your treatment and the likely outcome. But the position of the tumour in the brain is also very important. For example, brain stem gliomas are particularly difficult to treat, whatever their grade. The brain stem is a very complicated and delicate part of the brain and completely removing the tumour is not likely to be possible. Unfortunately, high doses of radiotherapy are not recommended either because this may cause too much damage to the normal brain stem.

 

Astrocytomas (including glioblastoma multiforme)

Astrocytomas are the most common type of glioma in both adults and children. A third of all brain tumours (34%) are astrocytomas. They develop from cells called astrocytes. The astrocytes are the cells of the brain that support the nerve cells (neurones). Astrocytomas can be slow growing (low grade) or fast growing (high grade). Some are very localised (focal). This means it is easy to see the border between the tumour and normal brain tissue on a scan or during an operation. Focal astrocytomas are more often diagnosed in children and are not common in adults. 

Other astrocytomas are called diffuse. These do not have a clear boundary between the tumour and normal brain tissue.

Anaplastic astrocytoma (also called grade 3 astrocytoma) and glioblastoma multiforme (GBM or grade 4 astrocytoma) are the most common type of brain tumour in adults. These are malignant (high grade) brain gliomas. They can sometimes spread to other parts of the brain.

 

Oligodendrogliomas

About 3 out of every 100 brain tumours (3%) are oligodendrogliomas. These develop from cells called oligodendrocytes. These cells make a white fatty substance that covers nerves, called myelin. It helps the nerve signals (impulses) to travel along the nerves more quickly. 

Oligodendrogliomas are most often found in the cerebrum, in the temporal or frontal lobes. They can be fast or slow growing. They are most likely to be diagnosed in adults, although they do occur in young children. Sometimes this tumour can spread within the central nervous system, in the fluid that circulates round the brain and spinal cord.

 

Ependymomas

About 2 out of every 100 brain tumours (2%) are ependymomas. These develop from cells called ependymal cells. These cells line the fluid filled areas of the brain (the ventricles) and the spinal cord. Their job is to repair any damaged nerve tissue.

Most ependymomas are diagnosed in children or young adults and can occur in any part of the brain or spinal cord. In older patients they tend to occur in the lower part of the spinal cord. Ependymomas can be high or low grade, but the cells' appearance under a microscope does not always fit with their behaviour. So the grade may not tell you much about how likely the tumour is to grow or spread. 

Rarely, ependymomas can spread to other parts of the central nervous system, through the fluid that circulates around the brain and spinal cord.

 

Unspecified gliomas

Around 6 out of every 100 brain tumours (6%) are unspecified gliomas. Unspecified glioma means that the cells are glioma cells but the doctor cannot tell exactly which type they are. Or the tumour may contain 2 or even 3 of the different types of glioma cells. The cell types can be different grades too. Your doctor will look at the different types of glioma cells and give you the treatment that is appropriate for the most aggressive cell type in your brain tumour.

 

Meningiomas

About 1 in 4 brain tumours in adults (25%) is a meningioma. They are more common in older people and in women. These tumours start in the tissues covering the brain (membranes). They are most often found in the cerebrum or cerebellum. They are usually benign (not cancerous) but some are atypical. This means that they behave more aggressively than normally expected for meningiomas. They can grow into surrounding brain tissue and may come back after they have been removed.

Meningioma symptoms vary a lot depending on their position in the meninges.

 

Haemangioblastomas

Only 2 out of every 100 brain tumours (2%) are haemangioblastomas. They grow from blood vessel cells. They are very slow growing and do not spread. But they can grow in the brain stem and then they are very difficult to treat. Sometimes these brain tumours can be part of a rare syndrome called von Hippel Lindau syndrome (vHL) which runs in families. People with vHL who develop haemangioblastoma may have more than one. Not everyone with vHL will get haemangioblastomas – the condition behaves differently in different people.

 

Acoustic neuromas

Acoustic neuromas are also called vestibular schwannomas. They start in the nerve that runs from the ears to the brain and controls hearing and balance. They are nearly always slow growing, do not spread, and are thought of as benign brain tumours. Often, they have been there a long time by the time they are diagnosed. 

Acoustic neuromas are found most often in older people. Loss of hearing in one ear can be a sign of acoustic neuroma. Rarely, they are associated with one form of a genetic condition called neurofibromatosis type 2 (NF 2). In these cases, they are usually diagnosed at a much younger age, can be on both sides (bilateral), and people affected may also develop meningiomas.

 

Craniopharyngiomas

Craniopharyngiomas are very rare benign tumours. Around 12 people are diagnosed with this type of tumour in the UK every year. These tumours tend to grow near the base of the brain, just above the pituitary gland. They are most often diagnosed in children, teenagers and young adults. 

Craniopharyngiomas do not usually spread, but they occur close to important structures in the brain and can cause problems as they grow. They can cause changes in hormone levels and problems with eyesight. Children with craniopharyngioma can have weight gain and growth problems.

 

Lymphomas

Sometimes lymphoma can start in the brain or spinal cord. This is called primary cerebral lymphoma or primary central nervous system (CNS) lymphoma. Fewer than 1 in 20 brain or spinal cord tumours (5%) are primary CNS lymphomas. Most are a type of lymphoma called diffuse large B cell non Hodgkin lymphoma.

Lymphoma is a cancer of the lymphatic system. These tumours are treated differently to other types of brain tumour. There is a section about non Hodgkin lymphoma on this website, including treatment information.

 

Germ cell tumours

Germ cell tumours account for about 2 out of 100 (2%) of all brain tumours. Around half of these tumours occur in young people between 10 and 20 years old. 

A germ cell tumour grows from primitive developing cells that form in the embryo and develop into the reproductive system. They are also called embryonal tumours. Most occur outside the brain, in the chest or abdomen, but they can occur in the brain. In the brain they are most commonly found in the area close to the pineal gland and the pituitary gland

Germ cell tumours sometimes produce chemicals that can show in the blood. The chemicals include alpha fetoprotein (AFP), human chorio gonadotrophin (HCG) and placental alkaline phosphatase (PLAP). So sometimes these tumours can be diagnosed with a blood test. They are often picked up when they are still small. They can block the circulation of fluid around the brain and so they tend to cause symptoms early on.

 

Pituitary tumours

About 8 out of 100 tumours (8%) are in the pituitary gland. They are more common in older people. The pituitary gland is attached to the underside of the brain. It lies in a small hollow in the skull, just behind the eyes. It controls many body functions by making and releasing chemical messengers (hormones) into the bloodstream. The pituitary hormones travel in the blood to other glands in the body, such as the thyroid, ovaries and testicles. The pituitary hormones control the amounts of other hormones that these glands make and release into the blood.

Most pituitary tumours develop from the gland tissue and are called adenomas. They are nearly always benign, so they grow slowly and tend not to spread. Pituitary tumours can often cause quite odd symptoms because the tumour cells make too much of one of the pituitary hormones. Doctors call tumours that make extra hormones which cause symptoms functioning tumours. These are sometimes also called neuroendocrine tumours.

 

Pineal region tumours

The pineal gland is in the middle of the brain, just behind the top of the brain stem. It makes the hormone melatonin. Pineal tumours are rare and account for only 1 to 2 out of every 100 brain tumours (1 to 2%). Several different types of tumour can grow in the pineal region, including gliomas. The most common types are germ cell tumours.

 

Primitive neuroectodermal tumours (including medulloblastoma)

Sometimes called PNETs, these tumours develop from cells that are left over from the earliest development of the body in the womb. Normally, these cells are harmless. But sometimes they can become cancerous. 

Medulloblastoma is the most common type of PNET. These grow in the cerebellum (the hindbrain). They are the second most common brain tumour in children, but the most common malignant (high grade) childhood brain tumour. Medulloblastomas are also diagnosed in young adults. These tumours can be fast growing and can spread to other parts of the brain and to the spinal cord through the cerebrospinal fluid (CSF).

 

Haemangiopericytomas

Fewer than 1 in 100 tumours of the brain and spinal cord are haemangiopericytomas. They start from cells called pericytes in the walls of tiny blood vessels (capillaries). They are a type of sarcoma and occur mostly in the meninges (the membranes covering the brain and spinal cord). They tend to be quickly growing tumours and are likely to spread to other parts of the brain or spinal cord. Sometimes they can spread outside the brain and spinal cord.

 

Spinal cord tumours

Up to 1 in 5 central nervous system tumours (20%) are in the spinal cord. There are a few different types. The success of treatment depends on the type of spinal cord tumour.

Meningiomas and neurofibromas are the most common types seen in adults. They grow outside the spinal cord but press on it. Astrocytomas and ependymomas grow in the spinal cord tissue itself. These are the most common types in children. Another rare type is called a chordoma.

 

Uncertain or unknown brain tumours

It is not always possible to find out the type of brain tumour you have. This may be because the tumour is in a delicate part of the brain that a surgeon is unable to operate on. These are called unspecified type brain tumours. Up to 1 in 6 brain tumours (around 14%) may be unspecified.

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Updated: 26 November 2013