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Glossary of Brain Tumour Terms

16,000 people diagnosed with a brain tumour every year

Glossary of Brain Tumour Terms

Types of brain tumours

There are many different types of brain tumours – the WHO have listed over 120 in their 2016 guidelines. The type of tumour depends on its location within the brain, the cells from which it originated, the pathology and its genetic make-up. This will also influence the shape and size of the tumour as well as its growth rate. Tumours can be classified as low-grade or high-grade, depending upon their nature.

Low-grade tumours

Grade I (1) — the tumour grows slowly and rarely spreads into nearby tissues. Depending on its location, it should be possible to remove the entire tumour by surgery.
Grade II (2) — the tumour grows slowly, but may spread into nearby tissue and the tumour may regrow at some stage following surgery. Some tumours may develop to form a higher-grade tumour.

High-grade tumours

Grade III (3) — the tumour cells grow quickly, are likely to spread into nearby tissue, and the tumour cells look very different from normal cells.
Grade IV (4) — the tumour grows and spreads very quickly. These tumours can be difficult to treat and not be removable by surgery, depending on the size, location within the brain and the extent to which they have invaded the surrounding tissue.

Benign tumour

This term is usually used to describe a low-grade tumour which grows slowly and is unlikely to invade into the surrounding brain tissue.

Malignant tumour

These are high grade tumours where the cells are growing rapidly and are actively invading neighbouring brain tissue.

Association of Medical Research Charities (AMRC)

This is a coalition of UK research funding charities. There 140 member charities, who together spend over £1.4bn a year on research here in the UK. In order to join the AMRC, a charity has to demonstrate transparency by the use of peer review of all research applications, as well as publishing a research strategy. Research funded by an AMRC member attracts an additional 26% of its value to cover the cost of University overheads and this is funded by the Charity Research Support Fund.

Blood-Brain Barrier

Because it is so sensitive, the brain needs to be protected from toxic factors which may be present in the blood. So, a specific membrane called the blood-brain barrier surrounds the blood vessels within the brain to prevent the passage of these agents into the brain. However, it can also prevent certain drugs from entering the brain and this is why some drugs, which have been developed for other tumours, are ineffective for the treatment of brain tumours.

Cannabis Oil

There is one cannabis-based drug, Sativex, which is licensed for the alleviation of spasticity in people with multiple sclerosis. The active ingredients, which are derived from the cannabis plant, are called cannabinoids. These compounds are also contained in cannabis oil, although usually at a much lower concentration. Some people have used cannabis oil as a potential treatment for their brain tumour, although there is no evidence that it is of benefit. Because cannabis oil is available to purchase without prescription, primarily over the internet, it is not considered as a medicinal product. Therefore, the quantity and nature of the cannabinoids present may vary and there is no quality control process to monitor the contents.


The use of drugs to treat cancer is referred to as chemotherapy. These drugs act to halt the growth of the tumour cells, or to kill them. While there are many different types of drugs available, the majority of these can’t be used for the treatment of brain tumours because they can’t cross the blood-brain barrier to get to the site of the tumour. The most common drug used for the treatment of brain tumours is temozolomide.


This refers to the removal of at least part of a tumour by surgery so that there is less tumour present for subsequent treatment by chemotherapy or radiotherapy. 


This is the study of the cells and tissues under a microscope. It involves the preparation of a thin slice of tumour tissue using a specialized cutting device and placing it on a glass microscope slide. This can then be examined in order to obtain specific information about a tumour such as its type and grade.


Although tumours are different to normal cells and should be identified as “foreign” by our immune system, they use specific mechanisms to prevent this from happening and essentially puts the immune cells near the tumour into hibernation. Immunotherapy refers to the reawakening of the immune system in order to allow it to attack the tumour cells. There are two main approaches being used. One stimulates the cells into action, and these drugs are called checkpoint inhibitors. An example of this is the drug nivolumab which has undergone clinical trials which were unsuccessful. However, other trials using similar drugs are in the planning stage. The second is to use a vaccination approach. This involves the generation of a part of the surface of the tumour that can be injected into the body to produce antibodies which can attack the tumour cells.

Liquid Aspirin

Soluble aspirin forms a suspension and appears as a cloudy solution rather than fully dissolving in water. Because it is not fully soluble, only a small amount will cross the blood-brain barrier to enter into the brain. By combining aspirin with another compound which itself has no action in the brain, researchers have developed a truly soluble form of the drug which is more likely to enter the brain. Initial studies using brain tumour cells grown in the lab suggest that this form of aspirin may kill the cells and trials are currently being planned to see whether this effect can be seen in the brain itself.

Myelin Sheath

Insulates the neurons in the brain in order to ensure that electrical impulses are carried safely and effectively.


A doctor who specialises in the prevention, diagnosis and treatment of cancer is called an oncologist. Those who focus on the treatment of brain tumours are referred to as a neuro-oncologist.


This is a new type of therapy called “Tumour Treating Fields”. It involves the placing of electrodes onto a person’s shaved skull which are then kept in place by a skin-tight cap. These are connected to a battery which is carried around for 18 hours per day. While the results look promising, further research is required in order to understand who would benefit from the treatment. The high cost makes it unlikely to be available on the NHS in near future.


This describes the study of various aspects of a disease including its cause, mechanisms of development, the structural alterations of cells and the consequences of the changes that are observed. It is mostly concerned with analyzing specific changes that have been identified as markers of a disease. A clinical pathologist will use a number of different techniques, including histology, in order to make a diagnosis and this will provide information on what treatment should be used. A pathologist works in close collaboration with clinical staff including oncologists.

Peer Review

It is vital that Brain Tumour Research only funds the highest quality research. Following submission, we send all funding applications to world experts in the specific field and ask them to examine the research proposals in detail. We will only fund research which has received the highest quality reviews from the experts.

Peripheral nervous system

The peripheral nervous system connects the central nervous system (CNS) that lies inside the brain and spinal cord, to other organs. 

Peripheral nerves are the 12 cranial nerves (that originate from the brain and brainstem), the nerves in the spine and the autonomic nerves. Autonomic nerves control automatic functions of the body such as regulating the muscles that control heartbeat, the muscles that line blood vessels (hence supporting blood flow around the body), and the functions of glands.

Proton beam therapy

This is a new form of radiotherapy which uses a specific form of radiation called proton beams. It is considered to be more accurate than existing radiotherapy with less damage to the tissue surrounding the tumour.


This is also referred to as radiation therapy and is a treatment using radiation as part of cancer treatment to control or kill tumour cells. It can be administered along with chemotherapy in certain forms of cancer. However, further research is required to identify which types of brain tumour will respond best to this form of therapy.


Surgery to remove part or all of a brain tumour.

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