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Malignant Brain Tumors. A primary malignant brain tumor is one that originates in the brain itself. Although primary brain tumors often shed cancerous cells to other sites in the central nervous system (the brain or spine), they rarely spread to other parts of the body.
Brain tumors are generally named and classified according to either of the following:
- The type of brain cells from which they originate
- The location in which the cancer develops
The biologic diversity of these tumors, however, makes classification difficult.
Secondary (Metastatic) Malignant Brain Tumors
A secondary (metastatic) brain tumor occurs when cancer cells spread to the brain from a primary cancer in another part of the body. Secondary tumors are about three times more common than primary tumors of the brain. Usually, multiple tumors develop. Solitary metastasized brain cancers may occur but are less common. Most often, cancers that spread to the brain to cause secondary brain tumors originate in the lung, breast, kidney, or from melanomas in the skin.
All metastatic brain tumors are malignant. This report discusses primary malignant brain tumors.
Primary Glioma Brain Tumors
About 80% of malignant primary brain tumors are known collectively as gliomas. Gliomas are not a specific type of cancer but are a term used to describe tumors that originate in glial cells. Glial cells are the building-block cells of the connective, or supportive, tissue in the central nervous system.
Gliomas are classified into four grades that reflect the degree of malignancy. Grades I and II are considered low-grade and grades III and IV are considered high-grade. Grades I and II are the slowest-growing and least malignant; grade I tumors are generally considered borderline between benign and malignant. Grade III tumors are considered malignant and grow at a moderate rate. Grade IV tumors, such as glioblastoma multiforme, are the fastest-growing and most malignant primary brain tumors.
There are several glial cell types from which gliomas form. The names of these gliomas and their cell types are:
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Review Date: 10/21/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
