What is a brain tumor?

A brain tumor is an abnormal growth or mass of cells in or around the brain. It is also called a central nervous system tumor.

Brain tumors can be malignant (cancerous) or benign (not cancerous). Some tumors grow quickly; others are slow-growing.

Only about one-third of brain tumors are cancerous. But whether they are cancerous or not, brain tumors can impair brain function if they grow large enough to press on surrounding nerves, blood vessels and tissue.

Tumors that develop in the brain are called primary tumors. Tumors that spread to the brain after forming in a different part of the body are called secondary tumors or metastatic tumors. This article focuses on primary tumors. There are more than 100 types of primary brain and spinal cord tumors.

How common are brain tumors?

Doctors diagnose brain tumors in about 85,000 people in the U.S. every year. Of those tumors, roughly 60,000 are benign, and about 25,000 are malignant.

Who is affected by brain tumors?

Brain tumors occur more often in men than women. Although they are most common among older adults, they can develop at any age. Brain tumors are the leading cause of cancer-related death in children under age 14.

What are the types of brain tumors?

Doctors classify brain and central nervous system tumors based on where they form and the kind of cells they involve.

Brain tumors that are usually benign include:

  • Acoustic neuroma: These tumors occur on the vestibular nerve (the nerve that leads from the inner ear to the brain). Acoustic neuromas are also called vestibular schwannomas.
  • Gangliocytoma: These central nervous system tumors form in neurons (nerve cells).
  • Meningioma: These are the most common type of primary brain tumors. Meningiomas develop slowly. They form in the meninges, the layers of tissue that protect the brain and spinal cord. In rare cases, a meningioma can be malignant.
  • Pineocytoma: These slow-growing tumors form in the pineal gland, which is located deep in the brain and secretes the hormone melatonin.
  • Pituitary adenoma: These tumors form in the pituitary gland, which is located at the base of the brain. The pituitary gland makes and controls hormones in the body. Pituitary adenomas are usually very small.
  • Chordoma: These slow-growing tumors typically begin at the base of the skull and the bottom part of the spine. They are mostly benign (not cancerous).

Cancerous brain tumors include:

  • Glioma: These tumors develop in glial cells, which surround and assist nerve cells. Two-thirds of cancerous primary brain tumors are gliomas. Types of gliomas include:
    • Astrocytoma: Astrocytomas form in glial cells called astrocytes.
    • Glioblastoma: Aggressive astrocytomas that grow quickly are glioblastomas.
    • Oligodendroglioma: These uncommon tumors begin in cells that create myelin (a layer of insulation around nerves in the brain).
  • Medulloblastoma: Medulloblastomas are fast-growing tumors that form at the base of the skull. These are the most common cancerous brain tumors in children.

What causes a brain tumor?

Doctors are not sure what causes most brain tumors. Mutations (changes) or defects in genes may cause cells in the brain to grow uncontrollably, causing a tumor.

The only known environmental cause of brain tumors is having exposure to large amounts of radiation from X-rays or previous cancer treatment. Some brain tumors occur when hereditary conditions are passed down among family members.

What are the symptoms of a brain tumor?

Some people with a brain or central nervous system tumor have no symptoms. In some cases, doctors discover a tumor during treatment for another issue.

As a brain tumor grows and presses on surrounding nerves or blood vessels, it may cause symptoms. Signs and symptoms of a brain tumor vary depending on the tumor’s location and type, size and what the affected part of the brain controls. They can include:

  • Headaches that are ongoing or severe; or that occur in the morning or go away after vomiting.
  • Behavior or personality changes.
  • Confusion.
  • Difficulty with balance or coordination.
  • Trouble concentrating.
  • Nausea and vomiting.
  • Numbness, weakness or tingling in one part or side of the body or face.
  • Problems with hearing, vision or speech.
  • Seizures.
  • Unusual sleepiness.
  • Trouble with memory, thinking, speaking or understanding language.

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