Gliomas are tumors that contain a variety of cell types, and the distribution of the cell types varies with each tumor. The most common type of gliomas are astrocytomas. They develop from abnormal, star-shaped cells.
Astrocytomas are graded on a scale of 1 to 4, grade 4 being the most malignant.
The types and grades of these tumors are:
- Well differentiated (low-grade or grade I and II) astrocytomas. These tumors contain cells that are less malignant than higher grade tumors. They grow slowly and can sometimes be completely removed by surgery. However, even well differentiated astrocytomas can be difficult to reach via surgery. If they are truly inaccessible, they can be life threatening.
- Anaplastic (grade III) astrocytomas. They grow more rapidly than the low-grade type, and contain cells that have malignant traits. Recommended treatment is surgery followed by radiation and chemotherapy.
- Glioblastoma multiforme (high grade or grade IV) astrocytomas. These tumors grow rapidly, invade nearby tissue and contain cells that are very malignant. Glioblastoma multiforme are among the most common and devastating primary brain tumors in adults. They are usually treated with surgery followed by radiation therapy. Chemotherapy may be used after radiation.
Mixed gliomas contain more than one type of glial cell, usually astrocytes and other glial cell types like oligodendroglial cells. Treatment focuses on the most malignant cell type found within the tumor. They may be classified under anaplastic oligodendrogliomas or be called mixed gliomas, depending on the relative cell types seen by the pathologist.
Brain Stem Gliomas
Named for their location rather than for the cells they contain, brain stem gliomas are most common in children and young adults. Surgery is not usually an option to treat these types of tumors because of their location in vital or critical areas. Radiation therapy sometimes helps to reduce symptoms and improve survival by slowing the tumor's growth.
Optic Nerve Gliomas
Also named for their location, these tumors are found on the optic nerve and are particularly common in individuals who have neurofibromatosis. Treatment may include surgery, radiation or chemotherapy. Some of these tumors can be very slow growing and best managed by observation alone.