Brain cancer & tumour definitions
A brain tumour (or “tumor” with the American spelling) is a mass of unnecessary and abnormal cells growing in the brain.
There are two basic kinds of brain tumours – primary brain tumours and metastatic brain tumours.
Brain tumours are categorised according to where the tumour originated, its pattern of growth and whether it is benign or cancerous. The tumour is also graded by its degree of malignancy and its chances of growing and spreading. There are approximately 130 different types of brain tumour. Names of the more common varieties include: gliomas (astrocytomas, glioblastomas, oligodendrogliomas, ependymomas and mixed cell type gliomas) meningiomas, medulloblastomas and central nervous system lymphomas.
Brain tumours can be benign or malignant. Malignant brain tumours are also called brain cancer.
Primary brain tumours
A tumour that starts in the brain is a primary brain tumour. Primary brain tumours may be grouped into "benign" and "malignant" tumours. Glioblastoma multiforme (GBM), astrocytoma, medulloblastoma and ependymoma are examples of primary brain tumours.
A benign tumour consists of very slow growing cells, usually has distinct borders, and rarely spreads. Treatment and/or surgery is often effective, however, if a benign tumour is located in a vital area of the brain, it can be considered life-threatening.
Malignant brain tumours vary widely both in the way they grow and the way they respond to treatment. Some are neatly contained within a capsule (encapsulated) and relatively easy to remove. Others have long, thin filaments spreading through the brain, like the roots of a plant.
- Slow growing
- Distinct borders
- Rarely spreads
- Usually rapid growing
- Life threatening
Metastatic brain tumours
Metastatic brain tumours begin as cancer elsewhere in the body and spread to the brain. All metastatic brain tumours are malignant since they begin as cancer elsewhere in the body. Most common metastatic brain tumours start in the lung, breast, colon (bowel), or skin (melanoma).
For more information about metastatic cancer visit Cancer Council Australia, or Cancer Australia.
Paediatric brain tumours
Children are different to adults—their bodies and brains are still developing. Their tumours are different too. The most common childhood brain tumours are not the same as the most common adult brain tumours.
Though rare, brain tumours are the most common form of solid tumours among children under
the age of 15.
Childhood tumours frequently appear in different locations and behave differently than brain tumours in adults. Treatment options vary depending on the type of tumour and age of the child. Children with tumours may also have a much better prognosis than adults with a similar condition.
To read more about childhood brain tumours, click here.
Grades of tumours
Tumours are graded according to how serious and advanced they are. Tumour grade is assigned based on the tumour’s microscopic appearance using some or all of the following criteria:
- similarity to normal cells (atypia)
- rate of growth (mitotic index)
- indications of uncontrolled growth
- dead cells in the centre of the tumour (necrosis)
- potential for invasion and/or spread (infiltration) based on whether or not it has a definitive margin (diffuse or focal)
- blood supply (vascularity).
Most doctors now use the World Health Organization (WHO) classification system to grade brain tumours.
WHO Grading System
Grade I Tumour:
- Slow-growing cells
- Almost normal appearance under a microscope
- Least malignant
- Usually associated with long-term survival
Grade II Tumour:
- Relatively slow-growing cells
- Slightly abnormal appearance under a microscope
- Can invade adjacent normal tissue
- Can recur as a higher grade tumour
Grade III Tumour:
- Actively reproducing abnormal cells
- Abnormal appearance under a microscope
- Infiltrate adjacent normal brain tissue
- Tumour tends to recur, often as a higher grade
Grade IV Tumour:
- Abnormal cells which reproduce rapidly
- Very abnormal appearance under a microscope
- Form new blood vessels to maintain rapid growth
- Areas of dead cells (necrosis) in centre
Another method of tumour classification is ‘staging’. To learn more about cancer staging click here.
Types of brain cancer
Astrocytomas grow from glial cells. Glia provide structure in the brain and spinal cord, and probably have other functions such as nourishing nerve cells and playing a role in learning and memory. Astrocytomas can occur in any part of the brain or spinal cord. They can either grow slowly, or grow rapidly and invade surrounding brain tissue.
CNS lymphoma is a disease in which malignant cells form in the lymph tissue of the brain and/or spinal cord. The lymph system is part of the immune system and is made up of the lymph, lymph nodes and vessels, spleen, thymus, tonsils and bone marrow. Lymphocytes (carried in the lymph) travel in and out of the CNS and in some cases become malignant.
Diffuse Intrinsic Pontine Glioma (DIPG)
An aggressive but rare tumour that arises in the glial tissue of the lowest, stem-like part of the brain which controls many of the body’s most vital functions. DIPG primarily affects children. Read more about childhood brain tumours here.
Ependymomas may originate from ependymal cells (which line the ventricles of the brain and the centre of the spinal cord) or from radial glial cells (cells related to early development of the brain). These are relatively rare tumours. Subependymomas are a Grade I type of ependymoma and usually occur near a ventricle.
Also called “astrocytoma, grade IV” and “glioblastoma multiforme” or “GBM”, glioblastomas commonly contain a mix of cell types. Glioblastoma cells are highly malignant; there are abnormal and numerous blood vessels and a high percentage of tumour cells are reproducing (dividing) at any given time. Necrotic (dead) cells may also be seen, especially toward the centre of the tumour. Glioblastomas are generally found in the cerebral hemispheres of the brain but can be found anywhere in the brain or spinal cord.
Glioblastoma Multiforme (GBM)
Another term for glioblastoma - see above. (The terms “glioblastoma multiforme”, “glioblastoma” and “grade IV astrocytoma” all refer to the same disease.)
The group of brain tumours that includes astrocytomas and oligodendrogliomas. Gliomas are the most common types of malignant brain tumours. Together, they make up about 40% of all primary brain tumours and around 70% of all primary malignant brain tumours (brain cancers).
Medulloblastomas are always located in the cerebellum. Medulloblastomas are fast-growing, high-grade tumours which frequently spread to other parts of the central nervous system. Given its location, close to one of the fluid cavities of the brain called the fourth ventricle, the tumour may also extend into that cavity and block the cerebrospinal fluid circulation or send cells through the spinal fluid to the spine.
These tumours arise from the arachnoid mater—one of the layers of the meninges (the lining of the brain). Anaplastic or malignant meningiomas (grade III) and papillary meningiomas are malignant and tend to invade adjacent brain tissue.
A mixed glioma containing a high proportion of both astrocytes and oligodendrocytes.
A type of tumour that is thought to grow from oligodendrocytes, which are cells that normally provide insulation to nerves in the brain.
More details about adult gliomas can be read or here.
It is not known what causes brain cancer; it appears to occur randomly. This is why we need to invest in research. For the vast majority of people with a brain tumour, no outside cause can be clearly identified.
Most astrocytomas and oligodendrogliomas occur when there is damage (a mutation) in genes that control how a cell grows and multiplies. The cells with the gene mutation develop into the tumour, but the abnormality cannot be inherited by the person’s children.
Known risk factors for astrocytomas and oligodendrogliomas include:
- ionising radiation (X rays and gamma rays)
- male sex (slightly higher risk than for females)
- genetically inherited tendency (rare).
Brain tumours are rare, so it is extremely difficult to collect information about a large enough group of cases to enable statisticians to make reliable conclusions. However, information is being collected around the world and here in Australia, and researchers plan to analyse data from a large number of patients with gliomas. Cure Brain Cancer is promoting collaboration within Australia and internationally to not only share discoveries and extend clinical trials but also to maximise the data available.
Research is underway into whether certain genes are important risk factors for brain tumours.
Read more about brain cancer research supported by Cure Brain Cancer.
Symptoms may be associated with the type, size, and/or location of the tumour. Symptoms may be caused by treatments used to manage it. Surgery, radiation, chemotherapy, and other treatments all have the potential to generate new symptoms as they work to reduce the impact of the tumour.
Common symptoms include:
- sensory (touch) and motor (movement control) loss
- deep venous thrombosis (dvt, or blood clot)
- hearing loss
- vision loss
- behavioural and cognitive (thinking) changes
- endocrine dysfunction (hormone/gland changes).
More information about brain tumour symptoms and diagnosis can be found here from the Brain Foundation or here from ABC2 , one of our international partners. For symptoms of childhood brain tumours click here for HeadSmart which defines the specific symptoms by age bracket.
Survival with a brain tumour
Survival time after treatment for a brain tumour varies and depends on several factors, including:
- the type of tumour
- the location of the tumour within the brain
- the tumour grade
- how much tumour was removed during surgery
- the person’s age
- the person’s general health.
It is difficult to predict accurately the outcome for a person with a brain tumour. Because each person’s circumstances are different, they may not give an accurate idea of survival time that can be expected for an individual.
Read more about support and care for people living with brain tumours here.
Read more about the facts and statistics regarding brain cancer here.
More comprehensive information about brain tumours can be found in the following booklets available for download:
“Understanding Brain Tumours - A guide for people with brain or spinal cord tumours, and their families and friends” Cancer Council NSW
"About Brain Tumors: A Primer for Patients and Caregivers" American Brain Tumor Association
“Adult gliomas: a guide for patients, their families and carers” Cancer Council Australia.
"2014 Literature Review: Current Knowledge in Brain Cancer Research" Cure Brain Cancer Foundation
The following are also useful sources of information about brain tumours and brain cancer in general:
Cancer Research UK
Johns Hopkins Brain Tumor Centre
Please note, whilst the above sources contain valuable information for patients and carers, they are based on the situation and standard of care in the USA, and as such the availability of treatment and what constitutes standard treatment and patient care processes often differs from those in Australia.