Brain Tumor Overview

A brain tumor is a mass of unnecessary, and often abnormal cells in the brain. There are many types of brain tumors. They may be primary brain tumors (originating in the brain) or metastatic brain tumors (traveling to the brain from another diseased part of the body). All primary brain tumors are either benign (slow growing, not cancerous) or malignant (growing quickly, cancerous).

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It is projected that over 186,000 brain tumors will be diagnosed in the United States in 2002. Of those, approximately 20% will be diagnosed with a primary brain tumor and 80% will be found to have a metastatic brain tumor.

Primary brain tumors, those that start in the brain, tend to stay in the brain. They can be either benign or malignant. However, a benign brain tumor, located in a vital area of the brain, could be life threatening. Malignant tumors, besides rapidly growing, are invasive and life threatening. They can spread to other locations in the brain and spine, but do not typically spread to other parts of the body.

Gliomas (including glioblastomas) account for more than 50% of all primary brain tumors, making them the most common primary brain tumors. Meningiomas and Pituitary tumors together represent nearly one-third of all primary brain tumors. Descriptions of these common tumors can be found on our website. In addition, further information is available on the American Brain Tumor Association website www.abta.org.

Metastatic (secondary) brain tumors begin as a cancer elsewhere in the body, such as in a lung, breast, or the colon, and then spread to the brain. By definition metastatic brain tumors are always malignant. The cancers that most commonly metastasize to the brain are breast and lung cancer. More information on metastatic brain tumors.

Primary brain tumors, such as Gliomas, are typically graded using the World Health Organizations (WHO) grading system. Tumors are graded to facilitate communication, to plan treatment and to predict outcome. The type and grade of a tumor also indicate its malignancy.

Grade I tumors are the least malignant, grow slowly and are associated with long-term survival.

Grade II tumors are relatively slow growing, but can sometimes invade adjacent normal tissue and recur.

Grade III tumors are malignant. These tumors typically recur and are actively reproducing to infiltrate adjacent brain tissue.

Grade IV tumors tumors are highly malignant and present with necrosis. They grow quickly and infiltrate widely.

A neuropathologist typically classifies tumors. This classification system is a subjective procedure that is not always straightforward, so different pathologists may disagree about the classification of the same tumor.

Patient prognosis is based upon the type of brain tumor, its grade, location, spread, age of the patient, how long the patient has had symptoms, the degree to which the brain tumor has impacted function as well as the extent of surgery performed, if any.