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Brain Tumors

  • Posted: 04/29/2009

Tumor Grades and Types

Tumor Grade
Types of Primary Brain Tumors

When most normal cells grow old or get damaged, they die, and new cells take their place. Sometimes, this process goes wrong. New cells form when the body doesn't need them, and old or damaged cells don't die as they should. The buildup of extra cells often forms a mass of tissue called a growth or tumor.

Primary brain tumors can be benign or malignant:

  • Benign brain tumors do not contain cancer cells:
    • Usually, benign tumors can be removed, and they seldom grow back.
    • Benign brain tumors usually have an obvious border or edge. Cells from benign tumors rarely invade tissues around them. They don't spread to other parts of the body. However, benign tumors can press on sensitive areas of the brain and cause serious health problems.
    • Unlike benign tumors in most other parts of the body, benign brain tumors are sometimes life threatening.
    • Benign brain tumors may become malignant.
  • Malignant brain tumors (also called brain cancer) contain cancer cells:
    • Malignant brain tumors are generally more serious and often are a threat to life.
    • They are likely to grow rapidly and crowd or invade the nearby healthy brain tissue.
    • Cancer cells may break away from malignant brain tumors and spread to other parts of the brain or to the spinal cord. They rarely spread to other parts of the body.

 Tumor Grade

Doctors group brain tumors by grade. The grade of a tumor refers to the way the cells look under a microscope:

  • Grade I: The tissue is benign. The cells look nearly like normal brain cells, and they grow slowly.
  • Grade II: The tissue is malignant. The cells look less like normal cells than do the cells in a Grade I tumor.
  • Grade III: The malignant tissue has cells that look very different from normal cells. The abnormal cells are actively growing (anaplastic).
  • Grade IV: The malignant tissue has cells that look most abnormal and tend to grow quickly.

Cells from low-grade tumors (grades I and II) look more normal and generally grow more slowly than cells from high-grade tumors (grades III and IV).

Over time, a low-grade tumor may become a highgrade tumor. However, the change to a high-grade tumor happens more often among adults than children.

You may want to read the NCI fact sheet Tumor Grade 1.

 Types of Primary Brain Tumors

There are many types of primary brain tumors. Primary brain tumors are named according to the type of cells or the part of the brain in which they begin. For example, most primary brain tumors begin in glial cells. This type of tumor is called a glioma.

Among adults, the most common types are:

  • Astrocytoma: The tumor arises from star-shaped glial cells called astrocytes. It can be any grade. In adults, an astrocytoma most often arises in the cerebrum.
    • Grade I or II astrocytoma: It may be called a low-grade glioma.
    • Grade III astrocytoma: It's sometimes called a high-grade or an anaplastic astrocytoma.
    • Grade IV astrocytoma: It may be called a glioblastoma or malignant astrocytic glioma.
  • Meningioma: The tumor arises in the meninges. It can be grade I, II, or III. It's usually benign (grade I) and grows slowly.
  • Oligodendroglioma: The tumor arises from cells that make the fatty substance that covers and protects nerves. It usually occurs in the cerebrum. It's most common in middle-aged adults. It can be grade II or III.

Among children, the most common types are:

  • Medulloblastoma: The tumor usually arises in the cerebellum. It's sometimes called a primitive neuroectodermal tumor. It is grade IV.
  • Grade I or II astrocytoma: In children, this lowgrade tumor occurs anywhere in the brain. The most common astrocytoma among children is juvenile pilocytic astrocytoma. It's grade I.
  • Ependymoma: The tumor arises from cells that line the ventricles or the central canal of the spinal cord. It's most commonly found in children and young adults. It can be grade I, II, or III.
  • Brain stem glioma: The tumor occurs in the lowest part of the brain. It can be a low-grade or high-grade tumor. The most common type is diffuse intrinsic pontine glioma .

You can find more information about types of brain tumors at http://www.cancer.gov/cancertopics/types/brain. Or, you can call the NCI Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).



Glossary Terms

anaplastic (A-nuh-PLAS-tik)
A term used to describe cancer cells that divide rapidly and have little or no resemblance to normal cells.
astrocyte (AS-troh-site)
A large, star-shaped cell that holds nerve cells in place and helps them develop and work the way they should. An astrocyte is a type of glial cell.
astrocytoma (AS-troh-sy-TOH-muh)
A tumor that begins in the brain or spinal cord in small, star-shaped cells called astrocytes.
benign (beh-NINE)
Not cancerous. Benign tumors may grow larger but do not spread to other parts of the body. Also called nonmalignant.
brain stem glioma (brayn stem glee-OH-muh)
A tumor located in the part of the brain that connects to the spinal cord (the brain stem). It may grow rapidly or slowly, depending on the grade of the tumor.
cancer (KAN-ser)
A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy.
cell (sel)
The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.
diffuse intrinsic pontine glioma (dih-FYOOS in-TRIN-sik PON-teen glee-OH-muh)
A type of central nervous system tumor that forms from glial (supportive) tissue of the brain and spinal cord. Diffuse intrinsic pontine glioma usually occurs in children. It forms in the brain stem.
ependymoma (eh-PEN-dih-MOH-muh)
A type of brain tumor that begins in cells lining the spinal cord central canal (fluid-filled space down the center) or the ventricles (fluid-filled spaces of the brain). Ependymomas may also form in the choroid plexus (tissue in the ventricles that makes cerebrospinal fluid). Also called ependymal tumor.
glioblastoma (GLEE-oh-blas-TOH-muh)
A fast-growing type of central nervous system tumor that forms from glial (supportive) tissue of the brain and spinal cord and has cells that look very different from normal cells. Glioblastoma usually occurs in adults and affects the brain more often than the spinal cord. Also called GBM, glioblastoma multiforme, and grade IV astrocytoma.
glioma (glee-OH-muh)
A cancer of the brain that begins in glial cells (cells that surround and support nerve cells).
grade (grayd)
A description of a tumor based on how abnormal the cancer cells look under a microscope and how quickly the tumor is likely to grow and spread. Grading systems are different for each type of cancer.
juvenile pilocytic astrocytoma (JOO-veh-NILE PY-loh-SIH-tik AS-troh-sy-TOH-muh)
A slow-growing type of central nervous system tumor that forms from glial (supportive) tissue of the brain and spinal cord. Juvenile pilocytic astrocytoma usually occurs in children and young adults. It forms in the brain more often than the spinal cord.
malignant (muh-LIG-nunt)
Cancerous. Malignant cells can invade and destroy nearby tissue and spread to other parts of the body.
medulloblastoma (MED-yoo-loh-blas-TOH-muh)
A malignant brain tumor that begins in the lower part of the brain and that can spread to the spine or to other parts of the body. Medulloblastomas are a type of primitive neuroectodermal tumor (PNET).
meningioma (meh-NIN-jee-OH-muh)
A type of slow-growing tumor that forms in the meninges (thin layers of tissue that cover and protect the brain and spinal cord). Meningiomas usually occur in adults.
oligodendroglioma (AH-lih-goh-DEN-droh-glee-OH-muh)
A rare, slow-growing tumor that begins in oligodendrocytes (cells that cover and protect nerve cells in the brain and spinal cord). Also called oligodendroglial tumor.
primitive neuroectodermal tumor (PRIH-muh-tiv NOOR-oh-EK-toh-DER-mul TOO-mer)
One of a group of cancers that develop from the same type of early cells, and share certain biochemical and genetic features. Some primitive neuroectodermal tumors develop in the brain and central nervous system (CNS-PNET), and others develop in sites outside of the brain such as the limbs, pelvis, and chest wall (peripheral PNET). Also called PNET.

Table of Links

1http://www.cancer.gov/cancertopics/factsheet/detection/tumor-grade