Brain Tumors Overview Primary

A brain tumor is a mass of abnormal cells growing in the brain that can be cancerous (malignant) or noncancerous (benign). A primary brain tumor originates in the brain, whereas secondary brain tumors—which are far more common—start in other organs or tissues and migrate to the brain.

Primary brain tumors may take years to grow large enough to cause serious symptoms. Some common symptoms include:

  • Balance problems
  • Behavioral changes
  • Nausea
  • Severe headaches
  • Speech difficulties.

Primary tumors rarely spread beyond the central nervous system. According to the National Cancer Institute, about 19,000 people are diagnosed with primary brain cancer each year in the United States.

Primary Tumor Definition and Origin

Primary brain tumors, also called “true brain tumors,” develop as a result of cellular and molecular DNA mutations, which allow cells to grow without restraint. Primary tumors can start in several different areas and tissues within or around the brain, including:

  • Blood vessels
  • Cranial nerves
  • Glial cells
  • Lymphatic tissue
  • Meninges (brain- and spinal cord-covering membranes)
  • Neurons
  • The pineal gland
  • The pituitary gland.

Primary brain tumors can affect any part of the brain. Brain tumors in children are usually found in the posterior cranial fossa, part of the intracranial cavity that contains the brain stem and cerebellum. In adults, brain tumors are generally located in the anterior (front) part of the cerebral hemisphere.

Types of Tumors in the Brain

Tumors in brain tissues are named for the cells from which they originate. Most primary tumors come from glial cells—cells that regulate homeostasis, produce myelin, and protect neurons—and are called gliomas. Types of primary brain tumors include:

  • Astrocytoma: Arises from star-shaped glial cells.
  • Brain cell glioma: Develops in the lowest portion of the brain.
  • Ependymoma: Forms in the central canal of the spinal cord.
  • Oligodendroglioma: Originates in the fatty protective, insulating covering of nerves.

Some brain tumors originate in non-glial cells. These include:

  • Craniopharyngioma: Grows at the base of the brain.
  • Germ cell tumor: Originates in the germ cells.
  • Medulloblastoma: Starts in the cerebellum (this is the most common brain tumor in children).
  • Meningioma: Grows very slowly in the meninges.
  • Pineal region tumors: Forms in the pineal gland between the cerebellum and the cerebrum.
  • Schwannoma (acoustic neuroma): Originates in the Schwann cells that line the nerve in the inner ear, which is responsible for balance and hearing.

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