Brain Tumor: Introduction

Approved by the Cancer.Net Editorial Board, 06/2016

ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Brain Tumors. To see other pages, use the menu. Think of that menu as a roadmap to this full guide.

The possibility of being diagnosed with a brain tumor is a shocking and life-changing event. If your doctor suspects a brain tumor, it is important to seek out doctors specialized in diagnosing and treating brain tumors. The brain is a complex and vital organ, and treatment often causes life-long changes.

About the brain and central nervous system

The brain and spinal column make up the central nervous system (CNS), where all vital functions are controlled. These functions include thought, speech, and body movements. This means that when a tumor grows in the CNS, it can affect a person's thought processes, the way they talk, or movements.

This section describes primary brain tumors, which are those that start in the brain. A primary brain tumor is described as low grade or high grade. A low-grade tumor generally grows slowly, but can turn into a high-grade tumor. A high-grade tumor is more likely to grow faster.

In adults, secondary brain tumors, also called brain metastases, are much more common than primary tumors. A secondary brain tumor is a cancerous tumor that started in another part of the body, such as the breast, lung, or colon, and then spread to the brain. Learn more about cancer that started elsewhere in the body and spread to the brain by reading about that specific type of cancer.

Anatomy of the brain

The brain is made up of 4 main parts: the cerebrum, the cerebellum, the brain stem, and the meninges.

  • The cerebrum. This is the largest part of the brain. It contains 2 cerebral hemispheres on either side of the brain that each control the opposite side of the body. It is divided into 4 lobes where specific functions occur:
    • The frontal lobe controls reasoning, emotions, problem-solving, expressive speech, and movement

    • The parietal lobe controls the sensations of touch, such as pressure, pain, and temperature. It also controls parts of speech, visual-spatial orientation, and calculation

    • The temporal lobe controls memory, special senses such as hearing, and the ability to understand spoken or written words

    • The occipital lobe controls vision

  • The cerebellum. The cerebellum is located at the back part of the brain below the cerebrum. It is responsible for coordination and balance and controls functions on the same side of the body.

  • The brain stem. This is the portion of the brain that connects to the spinal cord and the cerebellum. It controls involuntary functions essential for life, such as the beating of the heart and breathing. Messages for the functions controlled by the cerebrum and cerebellum travel through the brain stem to the body.

  • The meninges. These are the membranes that surround and protect the brain and spinal cord. There are 3 meningeal layers, called the dura mater, arachnoid, and pia mater. The cerebrospinal fluid (CSF) is made near the center of the brain, in the lateral ventricles. CSF circulates around the brain and spinal cord between the arachnoid and pia layers.

View illustrations of the anatomy of the brain.

Types of brain tumors

There are many types of primary brain tumors. Some cannot be assigned an exact type because the tumor’s location makes it too difficult to remove. For a complete list of the types of brain tumors and how often they are diagnosed, please refer to the Central Brain Tumor Registry of the United States.

This section’s coverage is divided into glioma and non-glioma types of tumors in adults. Learn about brain tumors in children.

Gliomas

As a group, a glioma is one of the most common types of brain tumor. A glioma is a tumor that grows from a glial cell. A glial cell is a supportive cell in the brain. The main types of supportive cells in the brain include astrocytes, oligodendrocytes, and ependymal cells. Gliomas may be considered astrocytomas, oligodendrogliomas, or ependymomas. Gliomas are assigned a grade, which is an indication of how aggressive a tumor is likely to be. A higher grade is usually more aggressive and more likely to grow quickly. However, doctors are moving toward using tumor genetics to better classify gliomas. This is discussed later in this guide.

Currently, the types of gliomas include:

  • Astrocytoma.  Astrocytoma is the most common type of glioma and begins in cells called astrocytes in the cerebrum or cerebellum. There are 4 grades of astrocytoma.

    • Grade I or pilocytic astrocytoma is a slow-growing tumor that is most often benign and rarely spreads into nearby tissue. It is more common in children.

    • Grade II or low-grade diffuse astrocytoma is a slow-growing tumor that can often spread into nearby tissue and can become a higher grade.

    • Grade III or anaplastic astrocytoma is a cancerous tumor that can quickly grow and spread to nearby tissues.

    • Grade IV or glioblastoma is a very aggressive form of astrocytoma.

  • Oligodendroglioma. Oligodendroglioma is a tumor that develops from cells called oligodendrocytes. These cells are responsible for making myelin. Myelin surrounds the nerves and is rich in protein and fatty substances called lipids. They are subclassified as either oligodendroglioma, which is considered low grade, or anaplastic oligodendroglioma.

  • Ependymoma. Ependymoma commonly begins in the passageways in the brain where CSF is made and stored, called the ependymal. In adults, they occur more often in the spine and tend to be of the myxopapillary subtype. Learn about ependymoma in children.

  • Brain stem glioma. A brain stem glioma begins in the glial cells in the brain stem. Learn about brain stem glioma in children.

Non-glioma tumors

The following section covers non-glioma tumors. These are tumors that arise from cells in the brain that are not glial or supportive tissue. Types of non-glioma tumors include:

  • Meningioma. Meningioma is the most common primary brain tumor. It begins in the meninges and is most often noncancerous. Meningioma can cause serious symptoms if it grows and presses on the brain or spinal cord or grows into the brain tissue. Learn more about meningioma.

  • Pineal gland and pituitary gland tumors. These are tumors that start in the pineal gland and pituitary gland.

  • Primary CNS lymphoma. This is a form of lymphoma. Lymphoma is a cancer that begins in the lymphatic system. Primary CNS lymphoma starts in the brain and can spread to the spinal fluid and eyes.

  • Medulloblastoma. Medulloblastoma is thought to start from a specific type of cell in the cerebellum. These cells are called cerebellar granule progenitor cells. It is most common in children and is usually cancerous, often spreading throughout the CNS. Similar tumors can start in other parts of the brain and are called primitive neuroectodermal tumors (PNET). Learn about medulloblastoma in children.

  • Craniopharyngioma. Craniopharyngioma is a benign tumor that begins near the pituitary gland located near the base of the brain. These tumors are rare. Learn about craniopharyngioma in children.

  • Schwannoma. Schwannoma is a rare tumor that begins in the nerve sheath, or the lining of the nerves. It may often occur in the vestibular nerve, which is a nerve in the inner ear that helps control balance. It is typically noncancerous.

Looking for More of an Introduction?

If you would like more of an introduction, explore these related items. Please note these links will take you to other sections on Cancer.Net:

  • ASCO Answers Fact Sheet: Read a 1-page fact sheet that offers an introduction to brain tumors. This fact sheet is available as a PDF, so it is easy to print out.

  • Cancer.Net Patient Education Video: View a short video led by an ASCO expert in this type of tumor that provides basic information and areas of research.

The next section in this guide is Medical Illustrations. It offers drawings of body parts often affected by this disease. Or, use the menu to choose another section to continue reading this guide.