The brain consists of many different cell types. The two major classes of cells are 1) neurons and 2) the cells that help to support and protect neurons, the glia. Primary brain tumors are those that develop from cells within the substance of the brain, as opposed to being derived from metastatic lesions that traveled from other original locations. Malignancies that are derived from the glia are referred to as gliomas.
Types of Gliomas
The glia of the central nervous system is not composed of a single cell type. There are two typical classes of glia. Oligodendrocytes normally produce the insulation, known as myelin, which wraps the signaling projections of nerve cells within the substance of the brain. Malignancies derived from oligodendrocytes are generally referred to as oligodendrogliomas. The other major type of glial cell within the brain is known as an astrocyte, so named because they can have a star-like appearance. Tumors derived from astrocytes are generally referred to as astrocytomas.
How Common Are Gliomas
Epidemiological data estimates that there will be more than 20,000 newly diagnosed cases of primary brain tumors in 2008 in the United States. Of these tumors approximately 40 to 50% will be gliomas. Dependent on cell of origin and degree of malignancy, gliomas can be subdivided into a number of different classes. These include tumors such as anaplastic astrocytomas, oligoastrocytomas and glioblastomas.
How Are Brain Tumors Characterized?
Examination of cells removed from a tumor via biopsy or at time of surgery provides an indication as to the degree of malignancy. If there are signs of high degrees of cell division and other features indicative of high levels of growth such as local invasiveness into surrounding normal tissue, the tumors are viewed to have high malignancy and great chance to recur, even with treatment. Of all the gliomas, probably the worst grade and type of tumor is that known as glioblastoma multiforme (GBM).
How Are Brain Tumors Treated?
Treatments for malignant gliomas depend both on the degree of malignancy and the location of the tumor. Tumors that are localized around or near to extremely important structures within the brain are often viewed as not able to be excised surgically because of the risk to surrounding structures. If the tumor is in an accessible location and does not impinge on critical structures surgical dissection is indicated. In a majority of cases, with or without surgical excision, combination radiation treatment and chemotherapy are used to combat the malignancy.
For additional information on gliomas and other brain tumors visit:
www.nci.nih.gov and www.braintumor.org
