The National Cancer Institute reports that more than 17,000 Americans are diagnosed with primary brain cancer each year. While brain tumors can develop at any age, studies show that they occur most commonly in children younger than eight years old and adults over age 65.
Tumors that originate in brain tissue are called primary brain tumors. When cancer develops elsewhere in the body and spreads (metastasizes) to the brain, it is known as a secondary brain tumor. The brain and spinal cord together make up the central nervous system.
Types of Brain Tumors
Primary brain tumors are categorized by the type of tissue in which they first develop. The most common brain tumors are called gliomas, which originate in the glial (supportive) tissue.
There are a number of different types of gliomas, including the following:
- Astrocytomas develop from small, star-shaped cells called astrocytes. They may arise anywhere in the brain or spinal cord. In adults, astrocytomas most often occur in the cerebrum, which is the largest part of the brain. The cerebrum fills most of the upper skull, and uses sensory information to tell us what is going on around us, and tell our body how to respond. The left hemisphere controls the muscles on the right side of the body, while the right hemisphere controls the muscles on the left. The cerebrum also controls speech and emotions, as well as reading, thinking and learning.
- Glioblastomas (also called glioblastoma multiforme or grade IV astrocytoma) are malignant astrocytomas that grow and spread aggressively. Glioblastomas occur most often in adults between the ages of 45 and 70.
- Brain stem gliomas arise in the brain stem, which controls many vital functions such as body temperature, blood pressure, breathing, hunger, and thirst. The brain stem connects the brain with the spinal cord. Tumors in this area can be difficult to treat. Most brain stem gliomas are high-grade astrocytomas.
- Ependymomas usually occur in the lining of the ventricles, or spaces in the brain and around the spinal cord. Although ependymomas can develop at any age, these tumors most commonly arise in children and adolescents.
- Oligodendrogliomas develop in the cells that produce myelin, the fatty covering that protects nerves in the brain and spinal cord. These tumors are very rare, and usually occur in the cerebrum. They are slow growing and generally do not spread into surrounding brain tissue. While they occur most often in middle-aged adults, these tumors have been found in people of all ages.