Types of Brain Tumors
What is a Brain Tumor?
A brain tumor is an abnormal growth of tissue in the brain. The tumor can either originate in the brain itself, or come from another part of the body and travel to the brain (metastasize). Brain tumors may be classified as either benign (non-cancerous) or malignant (cancerous), depending on their behavior.
A benign tumor does not contain cancer cells and usually, once removed, does not recur. Most benign brain tumors have clear borders, meaning they do not invade surrounding tissue. These tumors can, however, cause symptoms similar to cancerous tumors because of their size and location in the brain.
Malignant brain tumors contain cancer cells. Malignant brain tumors are usually fast growing and invade surrounding tissue. Malignant brain tumors very rarely spread to other areas of the body, but may recur after treatment. Sometimes, brain tumors that are not cancer are called malignant because of their size and location, and the damage they can do to vital functions of the brain.
Metastatic brain tumors are tumors that begin to grow in another part of the body, then spread to the brain through the bloodstream. Common types of cancer that can travel to the brain include lung cancer, breast cancer, melanoma (a type of skin cancer), and colon cancer. All of these cancers are considered malignant once they have spread to the brain.
Types of Brain Tumors
There are many different types of brain tumors. They are usually categorized by the type of cell where the tumor begins, or they are categorized by the area of the brain where they occur.
Astrocytomas are glial cell tumors that are derived from connective tissue cells called astrocytes. These cells can be found anywhere in the brain or spinal cord. Astrocytomas are the most common type of childhood brain tumor, and the most common type of primary brain tumor in adults. Astrocytomas are generally subdivided into high-grade, medium-grade or low-grade tumors. High-grade astrocytomas are the most malignant of all brain tumors.
Astrocytomas are further classified for presenting signs, symptoms, treatment, and prognosis, based on the location of the tumor. The most common location of these tumors in children is in the cerebellum, where they are called cerebellar astrocytomas. These persons usually have symptoms of increased intracranial pressure, headache, and vomiting. There can also be problems with walking and coordination, as well as double vision. In adults, astrocytomas are more common in the cerebral hemispheres (cerebrum), where they commonly cause increased intracranial pressure (ICP), seizures, or changes in behavior. Learn more about astrocytomas.
Brain Stem Gliomas
Brain stem gliomas are tumors found in the brain stem. Most brain stem tumors cannot be surgically removed because of the remote location and delicate and complex function this area controls. Brain stem gliomas occur almost exclusively in children; the group most often affected is the school-age child. The child usually does not have increased intracranial pressure (ICP), but may have problems with double vision, movement of the face or one side of the body, or difficulty with walking and coordination.
The most common type of primary brain tumor is a glioma. Gliomas begin from glial cells, which are the supportive tissue of the brain. There are several types of gliomas, categorized by where they are found, and the type of cells that originated the tumor.
Glioblastoma multiforme (GBM) is the most common glioma (a type of brain cancer). It represents nearly one fourth of all primary brain tumors. This cancer starts in the glial cells, which are cells that help nerve cells work.
Learn more about GBM .
Ependymomas are also glial cell tumors. They usually develop in the lining of the ventricles or in the spinal cord. The most common place they are found in children is near the cerebellum. The tumor often blocks the flow of the CSF (cerebral spinal fluid, which bathes the brain and spinal cord), causing increased intracranial pressure. This type of tumor mostly occurs in children younger than 10 years of age. Ependymomas can be slow growing, compared to other brain tumors, but may recur after treatment is completed. Recurrence of ependymomas results in a more invasive tumor with more resistance to treatment. Two percent of brain tumors are ependymomas.
Hemangioblastomas are tumors usually located in the cerebellum and spinal cord. They can cause significant problems, for example angiomas in the brain or spinal cord may press on nerve or brain tissue. The tumors can occur as the result of von Hippel-Lindau disease.
Optic Nerve Gliomas
Optic nerve gliomas are found in or around the nerves that send messages from the eyes to the brain. They are frequently found in persons who have neurofibromatosis, a condition a child is born with that makes him/her more likely to develop tumors in the brain. Persons usually experience loss of vision, as well as hormone problems, since these tumors are usually located at the base of the brain where hormonal control is located. These are typically difficult to treat because of the surrounding sensitive brain structures.
This type of tumor also arises from the supporting cells of the brain. They are found commonly in the cerebral hemispheres (cerebrum).are a very common symptom of these tumors, as well as headache, weakness, or changes in behavior or sleepiness. This tumor is more common in persons in their 40s and 50s. These tumors have a better prognosis than most other gliomas, but they can become more malignant with time.
Uveal melanoma is cancer (melanoma) of the eye. Common surgical treatment for uveal melanomas is enucleation (removal of the eye), and other therapeutic options include radium plaque therapy and proton beam therapy. Gamma Knife surgery is becoming a more frequently used procedure for this unusual condition.
What Causes a Brain Tumor?
The majority of brain tumors have abnormalities of genes involved in cell cycle control, causing uncontrolled cell growth. These abnormalities are caused by alterations directly in the genes, or by chromosome rearrangements which change the function of a gene.
Genetics: Patients with certain genetic conditions (i.e., neurofibromatosis, von Hippel-Lindau disease, Li-Fraumeni syndrome, and retinoblastoma) also have an increased risk to develop tumors of the central nervous system. There have also been some reports of people in the same family developing brain tumors who do not have any of these genetic syndromes.
Chemical Exposure: Research has been investigating parents of children with brain tumors and their past exposure to certain chemicals. Some chemicals may change the structure of a gene that protects the body from diseases and cancer. Workers in oil refining, rubber manufacturing, and chemists have a higher incidence of certain types of tumors. Which, if any, chemical toxin is related to this increase in tumors is unknown at this time.
Radiation: Patients who have received radiation therapy to the head as part of prior treatment for other malignancies are also at an increased risk for new brain tumors.