What Is a Brain Tumor?
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Medically reviewed by Gagandeep Brar, MD
A brain tumor is a group of abnormal cells that form in or near your brain. Unlike healthy brain cells, the cells that comprise a brain tumor are damaged. They multiply out of control without the normal cell functions that control their growth.
Brain tumors may start in your brain (primary tumors), or they can form from cells that move to your brain from cancer in another part of your body (secondary, metastatic tumors). Not all brain tumors are cancerous. Benign (noncancerous) tumors tend to grow slower and pose less risk than cancerous brain tumors.
Treatment varies by the size, type, and location of your brain tumor. It may or may not be linked to brain cancer. Outcomes also vary and can differ between two people with the same type of brain tumor.
This article describes brain tumor types, symptoms, causes, and treatments.
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Types of Brain Tumors
There are more than 150 types of brain tumors. Brain tumors are categorized by the type of cell that makes them up, how they act, and their characteristics when viewed under a microscope.
Benign Brain Tumors
Benign brain tumors account for about 71% of all brain tumors. They develop as a mass of noncancerous cells that grow inside your brain. Benign brain tumors tend to grow slowly and rarely spread outside your brain.
Malignant Brain Tumors
Malignant (cancerous) brain tumors originate from cancer cells. They often grow rapidly and can crowd surrounding tissue. Malignant brain tumors can extend "roots" that invade surrounding tissue and healthy brain tissue. They can also remain contained (encapsulated).
When malignant brain tumors develop or extend to areas of your brain that control important bodily functions, they can interfere with normal behavior and become life-threatening. These aggressive tumors can become dangerous quickly because they multiply and spread so fast.
Primary Tumors vs. Secondary Tumors
Primary brain tumors develop in the brain or its immediate surroundings. Abnormal growth of brain cells causes them. Primary brain tumors can be malignant or benign.
Primary brain tumors are classified based on the portion of the brain in which they originated. Categories of primary brain tumors include the following:
Glial: Glial brain tumors, called gliomas, are made up of glial cells, which are non-nerve cells in the central nervous system (brain and spinal cord) and the peripheral nervous system (outside the brain and spinal cord). They usually develop in the cerebral hemispheres of your brain.
Non-glial: Non-glial brain tumors develop on or in the nerves, blood vessels, glands, or other structures of the brain.
Secondary brain tumors, or metastasized brain tumors, develop by the spread, or metastasis, of cancer cells from other parts of your body. Secondary tumors are always malignant.
Secondary brain tumors are defined by the primary source of cancer that causes them. Cancers of the skin, lungs, breast, kidneys, and colon are some of the most common sources of secondary brain tumors.
If breast cancer spreads to the brain, the disease is called metastatic breast cancer because the cells in the secondary brain tumor are more like cancerous breast cells than abnormal brain cells.
Learn More:What Is Brain Cancer?
Brain Tumor Symptoms
Brain tumor symptoms will vary based on your tumor's size, type, and location. Symptoms can occur as sudden changes or develop so slowly over months or years that they remain unnoticed. You may not have symptoms of a brain tumor until the tumor starts to affect healthy tissue in your brain.
While symptoms of a brain tumor can vary widely, the following problems commonly occur with many types of brain tumors:
Frequent headaches that may worsen in the morning or awaken you at night and usually in combination with other symptoms
Seizures or convulsions with or without the loss of bodily function and/or consciousness
Nausea or vomiting
Problems swallowing or controlling your facial muscles
Difficulty speaking, articulating, remembering, or understanding others
Changes in your vision, especially abnormal eye movements or the onset of vision loss or double vision
Changes in your ability to hear
Numbness, tingling, or loss of sensation in your face, arms, or legs
Dizziness or loss of balance
Inability to walk normally due to problems such as dragging a leg
Changes in mood or personality, such as aggressiveness, disorientation, confusion, or sleeping issues for no apparent reason
Prolonged fatigue for no known cause
Paralysis or weakness in one part or one side of your body
Many brain tumor symptoms are nonspecific to this condition, meaning they could be caused by many other things. Having brain tumor symptoms doesn't always mean you have cancer. However, consult a healthcare provider if any of these symptoms don't improve or resolve and can't be explained by another diagnosis.
What Does a Brain Tumor Feel Like?
A brain tumor can feel different for everyone. While all brain tumors don't feel the same, they can produce the following sensations:
Seizures: Seizures are often the first warning sign of a brain tumor. Since a brain tumor usually involves one part of your brain, you may experience physical changes related to the part of the brain affected by your seizure. Rather than causing a tonic-clonic seizure that makes you lose consciousness, a brain tumor is more likely to cause a focal, or partial, seizure.
This can produce the following feelings:
A feeling of being absent from your surroundings
Déjà vu (a feeling that you have previously lived through your current situation)
Jamais vu (a feeling that you are experiencing something familiar for the first time)
Intense emotions
Numbness, tingling, or a burning sensation
Headache: You may experience a headache that feels different from others you've had. The pain of this type of headache may feel like a dull, persistent pressure. It may happen with nausea or vomiting. Your pain may worsen when you bend over, have a bowel movement, or lie down.
What Causes Brain Tumors?
While secondary brain tumors can be traced to the organ where the cancer started, most primary brain tumors can't be linked to a specific cause.
Research indicates that brain tumors occur when a brain cell's chromosomes become damaged and can't function normally. This damage may also affect the cell's ability to manage its growth. This can allow the damaged brain cells to divide rapidly and unchecked, eventually forming a tumor.
While the causes are unknown, certain factors can increase your chances of developing a brain tumor. These include the following known risk factors:
Radiation exposure to the brain (usually from prior treatment with radiation)
Weakened immune system
A family history of the following genetic conditions is also a risk factor:
Malignant and nonmalignant primary brain tumors affect 23 to 24 out of every 100,000 people in the United States. While brain tumors can affect anyone at any age, research shows that they are most common in children 3 to 12 years old and adults 40 to 70 years old.
Brain tumors occur more often in females (58%) than males (about 42%).
Note the when research or health authorities are cited, the terms for gender or sex from the source are used.
How Are Brain Tumors Diagnosed?
You will have to consult a healthcare provider for an accurate brain tumor diagnosis. Your healthcare provider will likely start with a physical exam and health history. This involves examining your body to check for general signs of disease. A history of your own health and your family's health, as well as your past illnesses, are also taken.
Based on the results of your physical exam, your healthcare provider will diagnose a brain tumor using several tools, including a neurological exam, imaging tests, and a biopsy.
Neurological Exam
A neurological exam is a noninvasive and painless exam. It includes a series of tests and questions to check for the normal function of your brain, spinal cord, and nerves. The exam assesses many aspects of your neurological health and cognitive abilities, including the following:
Alertness, concentration, and memory
Walking and coordination
Sensory function
Muscle strength and control
Balance
Imaging Tests
Imaging tests are used to determine the location and size of a brain tumor. It can also identify its characteristics and differentiate it from other types of tumors. This can help in determining the appropriate treatment and expected outcomes.
The following imaging tests are used in the diagnosis of brain tumors:
Magnetic resonance imaging (MRI): An MRI creates a series of detailed pictures of your brain and spinal cord using a magnet, radio waves, and a computer. It may be performed with or without a contrast medium called gadolinium. If a contrast medium is used, you will receive an injection before your scan. The injected substance is used to highlight cancer cells in the pictures.
Computed tomography (CT) scan: A CT scan uses a computer linked to an X-ray machine. It produces a series of detailed pictures of areas inside your brain taken from different angles. A dye may be swallowed or injected into your vein to help tissues or organs show up better in the pictures.
Positron-emission tomography (PET) scan: A PET scan involves the injection of a small amount of radioactive glucose into your vein. The PET scanner rotates around your body and produces a picture of where glucose is being used in your brain. Malignant tumor cells appear brighter in the images because they absorb more glucose. A PET scan can differentiate between a growing tumor and inflammation.
Biopsy
A biopsy is usually performed when imaging tests confirm the presence of a brain tumor or mass. This procedure is used to identify the type of tumor.
A biopsy involves removing a small piece of tumor tissue. The tumor tissue is analyzed by a pathologist, who examines it under a microscope and performs other lab tests to define the type of brain tumor.
The type of biopsy performed depends on the location of the brain tumor. The following techniques are used:
Stereotactic needle biopsy: A needle biopsy uses three-dimensional (3D) imaging to insert a hollow needle into the tumor and remove a tissue sample.
Neuroendoscopy: Neuroendoscopy is a form of endoscopic surgery. It involves the use of an endoscope, a thin tube with a camera and light on the end, to remove tumor tissue through a small opening in your skull.
Craniotomy: A craniotomy is a surgical technique that involves the removal of a piece of your skull to allow access to the tumor tissue so a portion can be extracted.
Lumbar puncture (spinal tap): A lumbar puncture removes a sample of spinal fluid to examine it for the presence of abnormal tumor cells.
How Serious Is a Brain Tumor?
Any type of brain tumor can be serious and even life-threatening, depending on its location. Your skull is an enclosed area with a finite amount of space. As any brain tumor grows, it can cause damage by pressing against normal brain tissue, your spinal cord, or your spine. It can also block the flow of fluid around the brain, increasing pressure inside it.
A malignant brain tumor carries the risk of damaging healthy brain tissue by spreading into other areas of your brain or spine. Depending on the areas of your brain the tumor affects, it can cause severe dysfunction by interfering with your brain's ability to control normal speech, movement, sight, or life-sustaining bodily functions.
Treatment for Brain Tumor
The type of treatment recommended for your brain tumor depends on the type of brain tumor and where it is located in your brain. Treatment of brain tumors usually includes radiation, chemotherapy, and/or surgery.
Some slow-growing, low-grade brain tumors can sometimes be left alone and watched closely. Or they may be removed with surgery before they grow and cause problems. Brain tumors that are more aggressive and higher grade may require another form of treatment after surgery.
Surgery
Surgery is usually the first treatment advised for brain tumors. In most cases, it is in your best interest to have complete or nearly complete surgical removal of a brain tumor.
Even if complete removal of the brain tumor is not possible to perform safely, surgery can often provide the following benefits:
Reduce the size of the tumor to be treated with radiation or chemotherapy
Create direct access to a tumor for the delivery of radiation or chemotherapy
Relieve symptoms like seizures
Help determine an appropriate treatment
Prevent progression
Maintain neurological function
The following techniques may be used to remove a brain tumor surgically:
Craniotomy: A craniotomy allows your neurosurgeon to locate the tumor and remove as much of it as possible.
Neuroendoscopy: The surgeon views and removes portions of the brain tumor through your nose or very small holes in your skull.
Laser interstitial thermal therapy (LITT) or laser ablation: Laser ablation delivers focused heat therapy to brain tumors while preserving the surrounding healthy brain tissue. It works by heating and destroying the brain tumor cells from the inside out. The procedure helps treat inoperable and recurrent brain tumors.
Other Therapies
Radiation therapy targets high-energy particles toward your brain tumor. It kills or shrinks brain tumor cells. Radiation therapy can be used as the first-line treatment for your brain tumor or it can be used to treat tumors that return after initial treatment.
The size, location, and type of your brain tumor determine which type of radiation therapy you receive. The following types of radiation therapy are used to treat brain tumors:
Standard external beam radiotherapy uses radiation beams to kill and shrink tumors while limiting the dose to surrounding areas of the brain.
Proton beam therapy uses charged particles called protons rather than the X-rays used in other forms of radiation therapy.
Stereotactic radiosurgery (Gamma Knife, Cyberknife, and Novalis) uses a highly focused beam of radiation to precisely destroy a section of tissue without incisions or a scalpel.
Chemotherapy is a systemic therapy that circulates throughout your bloodstream. It blocks or interferes with tumor cell growth. The following chemotherapy drugs are some of those used to treat brain tumors:
A combination of procarbazine, lomustine, and vincristine (PCV)
Gliadel (carmustine)
Avastin (bevacizumab)
Outlook for Brain Tumors
The outlook for different people with the same type of brain tumor can vary, so outcomes are difficult to generalize. The prognosis for someone with a brain tumor varies by tumor type and age at diagnosis. Survival rates for all types of brain tumors decrease with age.
The average five-year survival rate for all people with a primary brain tumor is 75.7%. A 2020 study found the average five-year survival rate for people with a nonmalignant tumor was 82.4%. The average five-year relative survival rate for people with a malignant primary brain tumor diagnosis in the study was 23.5%.
Survival rates cannot predict an individual's prognosis. As well, they don't reflect the outcomes of newer therapies.
If you or a loved one is diagnosed with a brain tumor, make sure the resources you consult are targeted to your condition. While all types of brain cancer are brain tumors, not all brain tumors are brain cancer.
Noncancerous (benign) brain tumors can have different treatment protocols and prognoses than cancerous brain tumors. In contrast to a cancerous brain tumor, a benign brain tumor usually grows slowly and is less likely to spread to other areas of your brain.
Summary
A brain tumor forms in or near your brain when damaged brain cells multiply and grow out of control. A brain tumor can occur without brain cancer. It can be malignant or benign.
Brain tumors that start in your brain are called primary tumors. They may or may not be cancerous. Brain tumors that form from cancer cells in another part of your body are called secondary brain tumors. These tumors are likely to be cancerous because they carry cells from the source to the brain.
Brain tumor treatment involves surgery, radiation, and/or chemotherapy. Treatment and outcomes vary by the size, location, and type of brain tumor you have. Age is also a factor. The prognosis for a person with a brain tumor declines with age.
Getting an early and accurate brain tumor diagnosis can help you get the right treatment. Early treatment of a brain tumor can help you avoid having the tumor damage brain function, cognitive/motor skills, or general health.
