To many, the mention of a brain tumor brings about a dire image, but a brain tumor does not always mean a cancer diagnosis. A tumor is a mass of abnormally dividing cells, and is either considered benign or malignant:
1. Benign Tumors
Benign tumors are slow growing, well-defined tumors that do not spread to other parts of the body. In rare cases, untreated benign tumors can be life-threatening if they affect a vital organ. Because they do not invade the surrounding tissue, benign tumors are relatively easy to remove with surgery, depending on their location. In some cases, benign tumors may become malignant, though this usually takes a long time, sometimes decades, if it happens at all. Benign tumors generally do not cause death or serious illness unless they are very large, such as some benign ovarian tumors, or if they affect a critical organ that makes it difficult to operate on and remove them, such as tumors in the brain.
2. Malignant Tumors
The term cancer is usually reserved for malignant tumors, which, like benign tumors, are masses of structurally abnormal cells growing uncontrollably. They differ, however, in their ability to invade the surrounding tissue and, in many cases, metastasize (spread) to different sites of the body via the blood or lymphatic system. This is one reason why surgical treatment alone for more advanced malignancies is often unsuccessful.
Because malignant cells have a tendency to spread from their original site, surgeons may leave them behind, which can result in new tumors in other locations. Malignancy often is treated by chemotherapy (systematic drugs aimed at killing deposits of cancer cells in sites other than the primary) or by radiation therapy applied over a broader area than that involve the main tumor.
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Brain tumors are described differently than tumors found in other parts of the body. A benign tumor will not spread to other parts of the body, but that does not mean that it is harmless. It can still grow and put pressure on tissue in the brain. This pressure can cause damage to healthy brain tissue and interrupt normal functions of the brain. In certain parts of the brain, the pressure interferes with vital functions, like breathing or heart rate, and can cause death.
Malignant tumors grow in an abnormal way and invade tissue around them. Brain tumors rarely spread to other areas of the body, but they can spread throughout the brain. Like benign tumors, damage caused by malignant tumors can cause severe disability and death.
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When Tom, now 51, first noticed symptoms of his benign brain tumor 9 years ago, they appeared out of the blue. “I had a 36-hour period during which I had repeated seizures called "absence seizures,” he says. “ I just wouldn't quite be there for a few minutes. Then I thought I heard a mouse in the dining room, though there was nothing there, and while I was down on the floor by the wall looking for it, I became aware that my wife was talking to me, but I was unable to answer her.”
Despite his diagnosis, Tom and his family continue to live a rich life as they weather the effects of his condition. He is presently on leave from his job as a chemistry lab director for a large pharmaceutical company, but he is still able to drive and maintain an active lifestyle.
Normal Anatomy and the Development of Brain Tumors
The brain and spinal cord make up the central nervous system (CNS). The CNS interprets sensory information, and regulates functions like body temperature, digestion, and coordinating physical movements. The brain also is responsible for memory, learning, and emotions.
Certain functions of the brain lie in specific areas. The 3 main areas of the brain and the functions that they are responsible for include:
The cerebrum is the control center for thought, reason, and speech. It processes sensory information from the body and houses the emotional center of the brain. It is divided into 2 large hemispheres, the right and left.
The cerebellum is located at the back of the head near the base. It primarily coordinates movement and balance.
- Brain Stem
The back and bottom portion of the brain that connects to the spinal cord at the base of the neck. Allows nerves to transmit messages back and forth to the brain. There are 3 parts to the brain stem— the pons, medulla oblongata, and midbrain. These structures control involuntary actions, such as breathing, digestion, and heart function.
Other nervous system structures include:
- Neurons - More commonly known as a nerve cell. Connected neurons create nerves and brain tissue.
- Meninges - Three layers of tissue that surround and protect the brain and spinal cord. The meninges lie inside the skull and spine.
- Skull - The bony shell that surrounds and protects the brain.
- Cerebrospinal fluid (CSF) - Clear, circulating fluid that surrounds, protects, and cushions the brain and spinal cord. CSF can be found inside the meninges.
- Blood-brain barrier (BBB) - A barrier that prevents certain substances in circulating blood from getting to the brain tissue. The BBB can keep out harmful substances like infections or toxins, but it also can block medications that may be helpful in treating brain conditions.
Cell division and cell death are a normal process in the body to replace old or damaged cells. Sometimes this division and new cell growth can continue after it is supposed to stop. This excess growth forms a tumor. Benign tumors grow in the area, but do not invade nearby tissue. Malignant tumors are cancers that do grow into nearby tissue. It is not always clear what causes the abnormal growth, but it often is a combination of genetic and environmental factors.
Are there different types of benign brain tumors?
The most commonly diagnosed benign brain tumors include:
- Meningioma - tumor arising from the membranes covering the brain and spinal cord; accounts for about 20% of brain tumors.
- Schwannoma (also called acoustic neuroma) - tumor in the 8th cranial nerve arising from Schwann cells (insulating cells of the nervous system); accounts for about 9% of all brain tumors.
- Pituitary Adenomas - pituitary gland tumor; accounts for about 8% of brain tumors.
- Hemangioblastomas - vascular tissue mass; accounts for about 2% of brain tumors.
- Craniopharyngioma - cystic tumor from cell remnants of Rathke's pouch (nasopharynx), usually occurring in children; accounts for about 1%-3% of brain tumors.
- Choroid Plexus Papilloma - choroid plexus tissue (responsible for the production of cerebrospinal fluid) mass that blocks cerebrospinal fluid flow, usually in children; accounts for less than 1% of brain tumors.
Risk Factors for Developing Brain Tumors
A risk factor is something that increases your chances of developing a certain disease or condition. Factors that increase your chances of a brain tumor are:
- Radiation exposure
- A condition that affects the immune system
- Family history of certain types of cancer
- Exposure to harmful chemicals like formaldehyde and vinyl chloride
Any cancer in the body can spread to the brain, but the most common include:
- Lung cancer
- Breast cancer
- Gastrointestinal tract cancer
- Kidney cancer
What are the symptoms of a benign brain tumor?
Some patients, like Tom, have symptoms that appear suddenly, while others may appear more gradually. The symptoms of benign brain tumors are sometimes difficult to read because they are found in other diseases as well. Alone, or in combination, these symptoms can be signs of a benign brain tumor:
- Vision problems
- Hearing problems
- Balance problems
- Changes in mental ability like concentration, memory, and/or speech
- Seizures, muscle jerking
- Change in sense of smell
- Facial paralysis
- Numbness in extremities
How are benign brain tumors diagnosed?
Your doctor will ask about your symptoms and medical history, and a physical examination will be performed. In addition, Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) brain scans may be used to confirm a suspected diagnosis. Benign brain tumors rarely develop into metastatic cancerous tumors. Most can be surgically removed, and usually do not reoccur after being removed.
How are benign brain tumors treated?
Most benign brain tumors are treatable. Treatment options are similar to other brain tumor treatments, and are based on the patient's age and overall health, and the location and size of the tumor. Typically, chemotherapy is not recommended in cases of benign brain tumors.
Primary treatments for benign brain tumors include:
- Brain Surgery (Craniotomy) - opens the skull and surgically removes as much of the tumor as possible.
- Shunt - implants a long thin tube in the brain to direct fluid build up to another part of the body
- Radiation Therapy - examples include conventional radiation, gamma knife, or proton beam.
- Medications - examples include corticosteroids that reduce edema, or swelling, and help the brain heal.
What are the survival rates for benign brain tumors?
Survival for patients with benign tumors is usually much better but, in general, survival rates for all types of brain cancers, benign and malignant, are:
- About 70% in children
- For adults, survival is related to age. Those ages 20-44 have a 5-year survival rate of about 50%, decreasing to a 5% 5-year survival rate in those over age 65.