What is a Brain Tumor?
A brain tumor is a group of abnormal cells that are growing and dividing without control inside the brain. As the cells keep doubling, they form a tumor—a lot of cells in a clump. Only abnormal cells do this. Normal cells only grow and divide when new cells are needed. A gene is a part of a cell that controls when the cell should grow and divide. When a gene is changed or damaged (a mutation), it no longer correctly controls a cell’s growth. Most brain tumors are caused by mutations in a gene that happen randomly, that is, without a known cause.

A very few brain tumors are caused by inherited diseases that have errors in genes. Families are usually aware of the inherited diseases, and know there is a chance of getting a brain tumor. Some of these diseases are:

• Neurofibromatosis, types 1 and 2
• Turcot’s syndrome
• Li-Fraumeni syndrome

What is a Secondary or Metastatic Brain Tumor?
Metastatic brain tumors are not caused by brain cells. They are tumors caused by cancer cells in other parts of the body. The cancer cells travel to the brain in the blood, get stuck there and grow into a tumor. The tumor is named by the tissue or organ the cancer cells spread from. For example, lung cancer that spreads to the brain and forms a tumor there is called, lung cancer metastatic to the brain. Cancers that commonly spread to the brain are:

• Lung cancer
• Breast cancer
• Colon cancer
• Melanoma (a type of skin cancer)

What is a Primary Brain Tumor?
A primary brain tumor is a tumor that starts in the brain. Primary brain tumors are much less common than metastatic brain tumors. There is about one primary brain tumor for every ten metastatic brain tumors.

Primary brain tumors are caused by abnormal brain cells that grow and divide without control. The abnormal cells form a tumor or lump in the brain that gets bigger as the cells continue to multiply.

There are several different types of brain cells, each with a special job.

• Neurons—nerve cells that do the jobs of the brain like thinking, memory, muscle control,  speaking, hearing, understanding language, seeing, tasting, and so on. Neurons rarely cause brain tumors.
• Glial cells—these are the support and protection cells for the neurons. There are three main groups of Glial cells:

• Astrocytes
• Oligodendrocytes
• Ependymal cells.

There are other subtypes of glial cells, but these three are the most frequent tumor-causing cells. Glial cells cause most primary brain tumors.

What are Primary Brain Tumors Called?

Glioma—name given to a brain tumor that is caused by abnormal glial cells.

Astrocytoma—starts from brain glial cells called “astrocytes.” Normal astrocytes are star-shaped cells that are the most common cell type to become brain tumors.

Oligodendroglioma—starts from brain glial cells called “oligodendrocytes.” Normal oligodendrocytes provide insulation around the electrically active neurons of the brain. These tumors are less common than astrocytomas.

Many tumors contain a mixture of astrocytoma and oligodendroglioma cells and are called “mixed gliomas” or “oligoastrocytomas.” Tumors of other brain cell types are much less common. For example, tumors of neurons are very rare in adults. We will call all of these simply “brain tumors.”

What are the Symptoms of a Brain Tumor?
Of the many symptoms that can be caused by a brain tumor, the most common are:

• Headache
• Nausea and vomiting
• Sleepiness
• Dizziness, coordination or balance problems
• Changes in vision (blurred or double vision)
• Confusion or other changes in thinking or speaking
• Seizures

These symptoms can also be caused by many different and more common illnesses. None of the symptoms is specific for brain tumors.

When a brain tumor is present, the symptoms from it are caused by pressure on the brain. The brain is a soft, delicate organ inside the hard skull. For protection, the brain is covered with thin layers of tissue and surrounded by a special fluid called Cerebro-Spinal-Fluid or CSF. The hard skull and the cushion of fluid keep the brain from getting bumped or bruised. The amount of space inside the skull cannot change, so if anything such as a tumor takes up space inside the skull, it puts pressure on the brain. The extra pressure is what causes the symptoms listed above.

How Is A Brain Tumor Diagnosed?
The diagnosis of a brain tumor begins with a doctor taking your medical history and doing a physical exam. Many questions are asked about your health and symptoms. For example, if your symptom is headache, the questions will be about how long the headaches have been happening, when during the day they occur, how long they last, what other symptoms happen along with the headaches, does anything relieve the headaches, what medications have you tried, and so on.

After your health history is completed, a thorough physical exam is done. The most important part of the physical exam is a test of all the brain and spinal cord functions. This is called a Neurological Exam.

When your history and physical exam are finished, some standard tests will be done. Blood tests and sometimes a chest xray are done to check your general state of health and to find other possible causes for your symptoms.

Other tests are done specifically for diagnosing a brain tumor. The most useful are a CT scan and an MRI of the brain. These imaging tests can show the size and location of a tumor. It also shows what effect the tumor may be having on other parts of the brain.

A brain MRI is similar to a CT scan, but the images are made with electromagnets instead of xrays. An MRI is done inside a tube-shaped space that may feel small to some people, and it is noisy because the magnets make a banging sound. The MRI shows different tissues in more detail than a CT scan. Both CT scans and MRIs are useful for showing the size and location of a brain tumor.

If A Brain Tumor Is Suspected, What Happens Next?
If a CT scan or MRI shows something that looks like a brain tumor, a biopsy needs to be done. To do a biopsy of a brain tumor, a neurosurgeon (brain surgeon) takes a sample of tissue from the tumor. The tumor sample is examined by a neuro-pathologist. This is a doctor who specializes in the study of brain and other nerve tissues. Using a microscope and other tools, the neuro-pathologist tries to answer the following questions.

1. Is the tumor a primary brain tumor, or is it a secondary or metastatic tumor that spread to the brain from a cancer somewhere else in the body?
2. What type of brain cells do the tumor cells look like?
   A tumor is named by the type of cells that are in the tumor.  For example, a brain tumor that is made up of cells that look like astrocytes is called an astrocytoma. Tumors with cells that resemble oligodendrocytes are called oligodendrogliomas. Many tumors contain a mixture of astrocytoma and oligodendroglioma cells and are called mixed gliomas or oligoastrocytomas.
   The three most common primary brain tumors in adults are astrocytoma, oligodendroglioma and mixed glioma (also called oligoastrocytoma)
3. Are there signs of newly formed blood vessels, and are the tumor cells growing and dividing quickly?

This information helps the neuro-pathologist decide the “grade” of the tumor. The grade is a measure of how abnormal the cancer cells look when compared to normal cells. The more abnormal the tumor cells are in size and shape, and the more they are dividing, the higher the grade of the cancer.

Brain tumors are graded from one to four, with one being the lowest grade and four being the highest grade. Low-grade brain tumors are grades one or two; high-grade brain tumors are grades three or four. Knowing the grade of the tumor is necessary for planning a patient’s treatment.

Putting the Information Together
The type of cells and grade of the tumor are put together to give the tumor a name. For example, “grade 4 astrocytoma” would mean a brain tumor formed by astrocytes that are dividing rapidly. Sometimes a brain tumor can have more than one name. Here is a list of common names of brain tumors:

• Anaplastic Astrocytoma is also called Grade 3 Astrocytoma
• Anaplastic Oligodendroglioma is the same as Grade 3 Oligodendroglioma
• Anaplastic Oligoastrocytoma, Grade 3 Oligoastrocytoma and Grade 3 Anaplastic Mixed Glioma are all names for the same tumor
• Glioblastoma is also Grade 4 Astrocytoma

(If the tumor name is confusing, ask to have it explained.)

Once a tumor has been given a name and a grade, the doctors who treat brain tumors can choose the best treatments for you and provide useful health-care information for you and your family.

Understanding Treatment for Brain Tumors >

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