Each year, approximately 3,000 Canadians are diagnosed with brain tumours. A glioma is a type of malignant brain tumour. A malignant tumour is a mass of abnormal cells that is cancerous.
Tumours can develop in any part of the brain or its nerves and covering tissues. The two major types of brain tumour are primary and secondary. Primary brain tumours start in the brain. Secondary brain tumours start in another part of the body, then spread to the brain. A glioma is a primary brain tumour, accounting for 45% of cancers that begin in brain cells.
The three main types of glioma include: astrocytoma, ependymoma, and oligodendroglioma. Each of these types can be assigned a grade, either low grade or high grade, with high grade being more malignant and aggressive.
Astrocytomas are named for the cells where they originate, the astrocytes. These tumours can either show clear borders between normal brain tissue and the tumour (called focal) or no clear border (called diffuse). Focal astrocytomas are most common in children and are not often found in adults. Glioblastoma multiforme, is the most common and most aggressive astrocytoma.
Ependymomas begin in cells called ependymal cells that are found lining certain areas of the brain and spinal cord. These cells help repair damaged nerve tissue. They usually occur in children and young adults.
Oligodendrogliomas form in oligodendrocyte cells, which produce a fatty substance called myelin that protects the nerve. More common in adults, these tumours may move to other parts of the brain or spinal cord.