Types of Brain Tumors
Brain tumors can be classified into two general groups: primary and secondary.
Primary Brain Tumors
Tumors that originate within brain tissue are known as primary brain tumors. Primary brain tumors are classified by the type of tissue in which they arise. The most common brain tumors are gliomas, which begin in the glial (supportive) tissue. There are several types of gliomas, including the following:
- Astrocytomas arise from small, star-shaped cells called astrocytes. They may grow anywhere in the brain or spinal cord. In adults, astrocytomas most often arise in the cerebrum. In children, they occur in the brain stem, the cerebrum, and the cerebellum. A grade III astrocytoma is sometimes called anaplastic astrocytoma. A grade IV astrocytoma is usually called glioblastoma multiforme.
- Oligodendrogliomas arise in the cells that produce myelin, the fatty covering that protects nerves. These tumors usually arise in the cerebrum. They grow slowly and usually do not spread into surrounding brain tissue.
- Ependymomas usually develop in the lining of the ventricles. They may also occur in the spinal cord. Although these tumors can develop at any age, they are most common in childhood and adolescence.
There are other types of brain tumors that do not begin in glial tissue. Some of the most common are described below:
- Meningiomas grow from the meninges. They are usually benign. Because these tumors grow very slowly, the brain may be able to adjust to their presence; meningiomas may grow quite large before they cause symptoms. They occur most often in women between 30 and 50 years of age.
- Schwannomas are benign tumors that arise from Schwann cells, which produce the myelin that protects peripheral nerves. Acoustic neuromas are a type of schwannoma. They occur mainly in adults. These tumors affect women twice as often as men.
- Craniopharyngiomas develop in the region of the pituitary gland near the hypothalamus. They are usually benign; however, they are sometimes considered malignant because they can press on or damage the hypothalamus and affect vital functions. These tumors occur most often in children and adolescents.
- Germ cell tumors arise from primitive (developing) sex cells, or germ cells. The most frequent type of germ cell tumor in the brain is a germinoma.
- Pineal region tumors occur in or around the pineal gland, a tiny organ near the center of the brain. The tumor can be slow growing (pineocytoma) or fast growing (pineoblastoma). The pineal region is very difficult to reach, and these tumors often cannot be removed.
Secondary Brain Tumors
Secondary brain tumors are tumors caused from cancer that originates in another part of the body. These tumors are not the same as primary brain tumors.
The spread of cancer within the body is called metastasis. Cancer that spreads to the brain is the same disease and has the same name as the original (primary) cancer. For example, if lung cancer spreads to the brain, the disease is called metastatic lung cancer because the cells in the secondary tumor resemble abnormal lung cells, not abnormal brain cells.
Treatment for secondary brain tumors depends on where the cancer started and the extent of the spread as well as other factors, including the patient's age general health, and response to previous treatment.