A tumour is an abnormal growth caused by cells reproducing themselves in an uncontrolled manner. The reason why brain tumours occur remains a mystery (research into environmental and genetic factors is limited) so there is no way to predict who will get brain tumour. The cause of a secondary brain tumour is always a primary cancer elsewhere in the body. There are many different types of brain tumour and they are usually named after the type of cell they started from.
Brain tumours are usually graded from 1 to 4. Tumour grades indicate the degree of malignancy and are based on their tendency to spread and the similarity to normal cells. Grade 1 and 2 are classified as low grade (benign or mildly malignant), and 3 and 4 as high grade, although there are some areas between 2 and 3 which can be difficult to distinguish. Some tumours contain several grades of cells, and the grade is determined by the most malignant grade of cell within the tumor, even if most of the tumour is lower grade.
Tumor diagnosis and grade are very important for both prognosis and treatment.
Primary Brain Tumours
These develop from brain cells. In other words, they develop in the brain and do not come from another cancer in the body.
Benign Tumours
Many tumours are benign (harmless) which means that they are not cancerous
and rarely spread (metastasise) into other parts of the brain or body. A
benign brain tumour has distinct boundaries and surgery alone may cure this
type of tumour. Some benign tumours may re-grow at a slow rate and further
surgery or radiotherapy may be necessary. If the tumour’s position
in the brain means that surrounding tissue could be damaged by surgery,
removal is not possible.
Malignant Tumours
A malignant primary brain tumour is life-threatening and likely to cause problems by invading and destroying surrounding normal brain tissue. Sometimes the cancer cells break away from the original tumour and spread to other parts of the brain or spinal cord.
Secondary Brain Tumours
These tumours start in another body organ such as the lung, breast, bowel or skin and then spread to the brain.
Symptoms
Brain tumours are often difficult to diagnose because their symptoms can be varied although in many cases people have headaches or nausea. The Trust has funded a three-year project to identify the problems with delays in diagnosis for children. This has led to our Pathways II project which provides more information on the symptoms to look for.
These symptoms are often caused by a rise in the pressure in the brain as the tumour grows. Raised intracranial pressure can also affect sight or balance or give rise to mental confusion. Another common symptom of the presence of a brain tumour is epilepsy which can cause muscle spasms, fits or moments of unconsciousness.
Symptoms Associated with the Position of the Tumour
Each area of the brain controls particular functions so a tumour can prevent a specific area of the brain from functioning normally. Here is a list of possible effects:
Brain stem: Lack of co-ordination when walking. Double vision. Difficulty in swallowing and speaking. Facial weakness – one-sided smile or drooping eyelid.
Cerebellum: Flickering, involuntary movement of the eyes (nystagmus). Vomiting and stiffness of the neck. Unco-ordinated walking and speech (dysarthria)
Temporal lobe: Speech difficulties and memory problems. Strange sensations – fear, blackouts, strange smells, déjà vu.
Occipital lobe: Gradual loss of vision on one side.
Parietal lobe: Problems with reading, writing or simple calculations. Difficulty in navigating one's way around. Numbness or weakness in one side of the body. Difficulty in understanding words or speaking.
Frontal lobe: Unsteadiness and weakness on one side of body. Changes in personality. Loss of smell.
Different types of brain tumours
Gliomas arise from the supportive tissue of the brain (glial cells) and account for more than half of all primary brain tumours. They may be named after the type of cell they are composed of or after the part of the brain where they are found.
Types of Glioma
Astrocytoma – developed from star-shaped cells called astrocytes. Grade 4 gliomas (also called glioblastoma multiforme) and grade 3 gliomas (also called anaplastic astrocytomas) are the most common type of brain tumour found in adults.
Mixed glioma – gliomas can be composed of a mixture of more than one type of glial cells, the most common of which are oligo-astrocytomas.
Oligodendroglioma – developed from cells known as oligodendrocytes which produce the fatty covering of the nerve cells known as the myelin sheath. These cells often grow more slowly than astrocytomas.
Ependymoma – developed from the ependymal cells which line the ventricles of the brain and the central canal of the spinal cord. These have the potential to send cells to other parts of the brain and spinal cord.
Other Tumour Types
Medulloblastoma (or PNET) – one of the most common and malignant tumours found in children. They usually develop in the cerebellum at the back of the brain and may spread to other parts of the brain.
Meningioma – developed from the meninges (the covering of the brain) and are usually slow growing. Most meningiomas are benign and do not spread from their original site.
Acoustic neuroma (or vestibular schwannoma, neurilemmoma) – develop in the acoustic or auditory nerve which controls hearing and balance. The nerve is covered by schwann cells.
Pituitary (or pituitary adenomas) - arising from the pituitary gland which produces hormones that control and regulate the other hormone-producing glands of the body.
Spinal – these press on the spinal nerves and can cause numbness, tingling, pain in the back, neck or limbs and, if in the lower part of the spinal cord, can lead to loss of bladder/bowel control.
For further helpful information on types of brain tumours, contact Cancerbackup on 0808 800 1234 for free booklets. Website: www.cancerbackup.org.uk.
