What Is a Benign Brain Tumor?

Benign tumors make up over half of the tumors Keck Medicine of USC doctors treat. Here’s what you need to know about treatment.

When faced with a brain tumor diagnosis, the first question patients ask is whether their tumor is cancerous or benign. Benign tumors are noncancerous, meaning they do not spread.  

“About half the tumors we treat are malignant or cancerous, and they either arise in the brain or spread from other cancers to the brain,” says Gabriel Zada, MD, a neurosurgeon and the director of the USC Brain Tumor Center, part of Keck Medicine of USC. “The other subset is tumors that are noncancerous and considered benign.”  

These types of tumors commonly occur in the skull base or in the lining of the brain, called the dura mater, which protects the brain and spinal cord. Common types include: 

• Chordomas 
• Meningiomas 
• Pituitary tumors 
• Schwannomas  

These tumors do tend to enlarge with age, but they can also affect people of all ages, Dr. Zada says.  

What causes benign brain tumors?  

While science has yet to determine exactly what causes benign brain tumors, some research has shown that in a small subset of people, there is a genetic cause. Neurofibromatosis 1, for instance, is a genetic disease that can cause benign tumors to occur in the nerves, brain and spinal cord. Children of people with this disease have a 50% chance of developing this type of benign brain tumor.  

One of the biggest risk factors for developing a benign brain tumor is radiation, Dr. Zada says. This can happen from radiation administered for another cancer or from radiation used in dental treatment.  

“If someone has radiation, especially as a child, that’s one of the biggest risk factors for developing adult brain tumors,” Dr. Zada says.  

Another known risk factor is certain hormone therapies. If a woman, especially one who already has a meningioma, undergoes a pregnancy or hormone therapy, she can be at risk of the tumor growing or enlarging, he says.  

Are benign tumors dangerous? 

“Just because tumors are benign does not mean they cannot be terrible diseases,” says Dr. Zada. “Meningioma is a great example of that. The tumor can be benign, but it can still grow in an invasive fashion. And just because it doesn’t spread to other parts of the body, like cancers often do, it can grow in areas of the brain where it cannot be removed or cured.” 

Do you always need surgery for a benign tumor?  

Many factors come into play when determining if a patient needs surgery to treat a brain tumor, Dr. Zada says. Examples include the location of the tumor, the tumor’s size and a patient’s age and symptoms.  

“Sometimes if the patient doesn’t have symptoms, we will monitor the tumor, have them get another MRI in six months or a year to check if it’s growing and then decide how to proceed,” he says. “Other times we know right away that they need surgery. For instance, if someone has a brain tumor that’s causing vision loss, that’s often – although not always – an indication to do surgery.” 

Some tumors can be treated with less-invasive procedures. Some tumors, for instance, are in a favorable location that allows them to be treated with pinpoint radiation called radiosurgery or stereotactic radiosurgery, Dr. Zada says. New treatments that can shrink a tumor, such as hormonal or medical therapies, are also increasingly available.  

“Treatment depends on so many factors – and, most importantly, on patient preference and quality of life,” Dr. Zada says. “We talk to the patients and make decisions about what the first step should be.” 

Can benign tumors become cancerous/malignant?  

Benign tumors can become cancerous after prolonged years or prolonged treatment.  

What new treatments are available for benign brain tumors?  

“We offer a variety of clinical trials for pituitary tumors,” Dr. Zada says. “There is also another USC-designed chemotherapy that can be inhaled to treat tumors at the base of the skull that is currently being tested.” To find an open clinical trial at Keck Medicine, visit https://clinicaltrials.keckmedicine.org/.

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