Understanding Brain Tumors

Stock photo of a smiling person who is wearing a scarf on their head

Brain tumors are complex conditions that can affect people of any age. Treatment advances — from precise surgery techniques to targeted chemotherapy — mean a better outcome for more patients. Important things to know:

  • There are dozens of brain tumor types. Doctors identify the type based on location in the brain, the type of cell it started in and its genetic traits.
  • Only some brain tumors are cancer. All tumors need treatment because they can damage brain tissue. It’s important to see a specialized team.
  • Symptoms, treatment options and outcomes depend on the tumor’s location and whether it’s slow-growing or aggressive.

What are brain tumors?

Brain tumors are masses of abnormal cells that grow out of control. Because the brain and spinal cord make up the central nervous system (the body’s control center), tumors found there are also called CNS tumors.

Benign versus malignant: Some brain tumors are benign (not cancer), and some are malignant (cancer). This matters less than for tumors in other parts of the body, because both types can be life-threatening. Doctors refer to brain tumors, not brain cancer.

  • Benign: These are slow-growing and unlikely to invade normal tissue. They can cause damage, though, by pressing on important parts of the brain.
  • Malignant: These are made of rapidly dividing, abnormal cells. They invade normal tissue but rarely spread outside the brain.

Primary versus secondary or metastatic: Primary brain tumors start in the brain. Secondary or metastatic brain tumors form from cancer that has spread from elsewhere in the body, most often from lung, breast or skin cancer. Secondary tumors are more common and require different treatment.

Who gets brain tumors?

According to the American Brain Tumor Association, about 80,000 brain tumors are diagnosed each year in the U.S. About two in three are benign. The most common primary tumors are meningiomas. They are usually benign and form in the tissue covering the brain.

Most of the time, doctors don’t know what causes brain tumors. They have few known risk factors. What doctors do know:

  • Age: Primary brain tumors are more common in children and older adults. Metastatic brain tumors are more common in adults than children.
  • Family history: Risk can rise with a family history of genetic conditions such as neurofibromatosis.  
  • Radiation therapy: Previous radiation therapy can increase risk.
  • Gender: Men have a slightly higher risk than women. But some tumors, such as meningiomas, are more common in women.

Survival rates for brain tumors

You may hear the term “five-year survival rate.” It refers to the portion of people alive at least five years after diagnosis. A 65% survival rate, for example, means 65 out of 100 people are alive five years later. Remember that the numbers are averages and can’t predict the outcome for an individual.

For brain tumors:

  • Outcomes vary widely: Survival rates vary by the type of tumor, its location and the patient’s age. Some types grow slowly and are easier to remove. Others are more aggressive or in a difficult place to reach. Examples:
    • Ependymoma: This type has a high survival rate, 92% for patients diagnosed from ages 20 to 44.
    • Glioblastoma: This aggressive type has a survival rate of 19% for the same age group.
  • Signs of hope: Survival rates for brain tumors have increased in recent decades, thanks to earlier diagnosis, better imaging, and more precise and effective treatments.
  • Quality of life: At OHSU, we are dedicated to giving you the longest, highest quality of life possible, regardless of your diagnosis.

Brain tumor staging

Brain tumors differ from other cancers because they rarely spread to other organs. Doctors do not stage them with the system used for other tumors. Instead, they use these factors to guide treatment:

  • Your age: Younger people usually have better outcomes.
  • Impact: How much your daily functioning is affected.
  • Tumor features: The tumor’s type, size and location.
  • Genetic factors: The tumor’s genetic traits.
  • Localization: Some tumors are in one part of the brain, while others may have spread to several sites.

Brain tumor grading

Doctors grade brain tumors on a scale of one to four. The lower the grade, the less aggressive the tumor and the easier it is to treat.

Tumors graded I or II are “low grade” and benign. Tumors graded III and IV are “high grade” and malignant. The World Health Organization defines grades as:

  • Grade I: Slow-growing. Cells look almost normal. Associated with long-term survival. Rare in adults.
  • Grade II: Relatively slow-growing. Cells look slightly abnormal. Can spread to nearby normal brain tissue and recur, sometimes returning as a higher-grade tumor.
  • Grade III: Cells look abnormal and are actively reproducing. They can grow into nearby normal brain tissue and are prone to recurring, often as a grade IV tumor.
  • Grade IV: Cells look highly abnormal and rapidly reproduce. Tumors form new blood vessels to support growth. They have dead cells (necrosis) in their centers. They can easily invade nearby normal brain tissue.

Brain tumor types

There are more than 150 types of primary brain tumors. They are classified by the type of cell they form from and their genetic traits.


These tumors form from glial cells, one of the two main types of cells in the central nervous system. Glial cells surround and support neurons, the other main type. Types of gliomas include:

  • Astrocytomas: These tumors start in cells called astrocytes. They can be difficult to surgically remove because the tumor tissue merges with regular brain tissue. Glioblastoma, an aggressive type of astrocytoma, is the most common malignant brain tumor in adults.
  • Oligodendrogliomas: These slow-growing tumors start in cells called oligodendrocytes. They can be difficult to surgically remove and may become more aggressive over time.
  • Ependymomas: These start in ependymal cells. They may be easier to remove because they don’t grow into regular brain tissue.


Types include:

  • Meningiomas: These are the most common type in adults. They begin in the meninges, the tissues that cover the brain and spinal cord. Doctors may be able to surgically remove Grade I meningiomas. Grade II and Grade III meningiomas can be removed but are more likely to come back.
  • Pineal gland and pituitary gland tumors: These are usually benign. They start in the pituitary gland and can cause symptoms by pressing on nearby structures or by producing too much of a hormone.
  • Primary CNS lymphoma: Lymphomas are blood cancers. When lymphoma starts in the central nervous system, it’s called primary CNS lymphoma. Chemotherapy is often the main treatment for this type.
  • Medulloblastomas: These start in cells in the cerebellum, the part of the brain that controls movement. They are aggressive and more common in children than adults. They can sometimes be treated with a combination of surgery, radiation therapy and chemotherapy.
  • Craniopharyngiomas: These Grade I tumors start between the pituitary gland at the base of the skull and the brain. They are more common in children than adults. They can be difficult to remove because they sit close to the optic nerves that give us vision, and the pituitary gland that produces hormones.
  • Schwannomas: These develop from Schwann cells, which surround the nerves that connect the brain to the rest of the body. They are most often Grade I tumors. Subtypes include vestibular schwannomas or acoustic neuromas, which occur when the tumor presses on the nerve responsible for balance and hearing.

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Portland, OR 97239
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