A brain tumour is a growth of cells in or around the brain which multiply in an abnormal, uncontrollable way. There are two major types of brain tumour: primary brain tumours and secondary brain tumours. Primary brain tumours arise from cells normally found in and around the brain. Secondary brain tumours (also called brain metastases) arise from the spread of cancer from another part of the body (e.g. lung cancer, breast cancer, skin cancer such as malignant melanoma). Secondary brain tumours are more common than primary brain tumours.
Primary Brain Tumours
There are four important factors that affect the management and outcomes of primary brain tumours: type of tumour, grade of tumour location of tumour and the general health of the patient.
Primary brain tumours arise from cells normally found in and around the brain with the different types of primary brain tumour named according to the type of brain cell they have grown from. More than half of all primary brain tumours are called gliomas (tumours arising from glial tissue, the tissue that binds nerve cells and fibres together). Gliomas most commonly arise from glial cells called astrocytes and/or oligodendrocytes. A glioma arising from an astrocyte is called an astrocytoma, while one arising from an oligodendrocyte is called an oligodendroglioma, and one arising from both cells is called an oligoastrocytoma (also referred to as a mixed glioma).
Primary brain tumours are also graded from 1 to 4 according to their behaviour, such as how fast they grow and how likely they are to spread. This grading system can be looked upon as a malignancy scale with Grade 1 tumours being the slowest growing, Grade 2 tumours being slow growing without frankly malignant cells but having the capacity to become malignant, Grade 3 tumours being more rapid growing and containing malignant cells, and Grade 4 tumours being the most rapidly growing frankly malignant tumours. The gliomas (astrocytomas or oligodendrogliomas or mixed gliomas) are graded from 2 to 4 with a Grade 4 astrocytoma being the most aggressive malignant type and also being called by its old name, Glioblastoma Multiforme. This grading of tumours is performed by the neuropathologist when they receive tumour tissue from the operating theatre. An X-Ray such as an MRI scan may give an indication as to the grading of an underlying tumour but this is not precise and can in some situations be misleading. Hence a final true grading of a brain tumour can only be provided by the neuropathologiost examining tumour tissue removed by the neurosurgeon. Gliomas are described as being Low Grade (Grade 2) or High Grade (Grade 3 or 4).
The location of primary brain tumours refers to their location in and around the brain. This affects the possibility of neurosurgical removal. A tumour found deep within the brain or in an eloquent area (area of the brain that has significant important control of bodily functions) nearer the surface of the brain will potentially not be possible to remove and/or will be associated with greater risk from operating. A tumour found nearer the brain surface in a non-eloquent area (area of the brain with minor functions) may be removed by the neurosurgeon with less risk to the patient. As a result, all brain tumours are potentially life threatening, as even a Grade 1 (slow growing tumour) may not be fully removed by the neurosurgeon because it is found it a deeper vital area of the brain.
Secondary brain tumours
Secondary brain tumours (also called brain metastases) arise from the spread of cancer from another part of the body (e.g. lung cancer, breast cancer, skin cancer such as malignant melanoma). Secondary brain tumours are more common than primary brain tumours. They are all malignant tumours. The treatment of secondary brain tumours depends on the type and location of the tumour(s) as with primary brain tumours, but also depends on the extent and control of the primary cancer and the presence or absence of spread of the cancer to other parts of the body. The primary cancer refers to the original cancer from where the secondary cancer spread such as the lung or breast or skin.
An overview is provided below of:
Links are also provided to more information on these conditions.
Generally, low-grade brain tumours - grade 1 or 2 - are slow growing and unlikely to spread. They are usually do not contain frankly malignant cells, which means they tend to stay in one place and do not invade other areas of the brain or spread to other parts of the body.
However, low-grade (Grade 2) gliomas will frequently grow back after treatment. More seriously, they can also mutate (change) into high-grade tumours (grade 3 or 4), which are fast-growing cancerous tumours that are likely to spread. About half of all low-grade (Grade 2 ) glioma tumours mutate in this way within five years of diagnosis.
If you have been diagnosed with a low-grade brain tumour, your treatment will depend on the type and location of the tumour and your outlook will depend on the location of the tumour, whether it grows back following treatment, and whether it mutates.
For more information, see the Health A-Z topic on low-grade/mixed brain tumours
High-grade brain tumours
High-grade brain tumours may be either:
- Primary tumours- these started in the brain and can spread to other parts of the brain or spine, but rarely to other areas of the body.
- Secondary tumours(brain metastases) - these started as cancer in another part of the body and spread to the brain through the blood.
There are different types of primary high-grade brain tumour, depending on the type of brain cells they have grown from. The most common type is a glioma, which accounts for more than half of all primary brain tumours. High grade gliomas are either Grade 3 or Grade 4 gliomas. About 300 new cases of high-grade glioma are currently recorded each year in Ireland. A primary high-grade brain tumour must be treated as soon as possible, because it can spread to and damage other parts of the brain and spinal cord. The treatment offered will vary according to the three factors discussed above: tumour type, tumour grade and tumour location along with the general health of the patient.
Secondary brain tumours are as serious as primary tumours. The treatment will vary according to the type of tumour (lung, breast etc), tumour location in the brain, the general health of the patient, the degree of control of the primary cancer and the presence or absence of spread of the cancer to other parts of the body.
For more information, see the Health A-Z topic on high-grade brain tumours