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Tuesday, October 25, 2011

Primary and Metastatic Brain Tumors

Primary and Metastatic Brain Tumors
What Is the Difference Between Primary and Metastatic Brain Tumors?

The terms primary and metastatic describe where the tumor has originated and brain tumors are generally classified as one or the other. Primary brain tumors arise from the brain or spinal cord while metastatic brain tumors arise from other tissue and have spread to the brain. This is the most basic form of classifying brain tumors, but yields great insight into the characteristics of these complex growths and how they might be treated.

Many people have the impression that all brain tumors are alike, regardless of where they began, but if you ask any neuro-oncologist they will tell you there are significant differences that do affect treatment.

Primary Brain Tumors
Primary brain tumors are those that originate in the brain and spinal cord (collectively known as the central nervous system, or CNS) and rarely spread outside of the CNS. They can develop in children and adults, but are considered to be rare in both populations. Primary tumors that that develop in children and adults differ - they usually develop in different parts of the brain, have varied treatment methods, and have different prognosis. Primary tumors can also be malignant (cancerous) or benign (non-cancerous).

Despite their rarity, the incidence of primary brain tumors is increasing. This is partly due to the fact that people now have a higher life expectancy and we are much more skilled in diagnosing brain tumors than in the past. The causes of primary brain tumors remains to be mainly unknown, however researchers believe that in some cases environmental exposures and genetics play a role in brain tumor development. Several different types of tumors can develop in the brain. The symptoms of primary brain tumors vary based on the location of the tumor and its size.

Metastatic Brain Tumors
Unlike primary brain tumors, metastatic brain tumors originate in another part of the body and spread to the brain. Many types of cancer can spread (metastasize) to the brain, but melanoma, breast, lung, and kidney cancer are among the most common. Cancer cells spread by blood or lymphatic vessels. Metastatic brain tumors are more common than primary brain tumors. It is believed that the commonality is not because cancer types are becoming more aggressive, it is just that people are living longer from their cancer types, and this time allows for metastasis to occur.

In some rare cases, a metastatic brain tumor is discovered before the originating cancer site is detected. In these instances, it is called "metastasis of unknown origin." Because metastatic brain tumors do not have the same cellular composition of primary brain tumors, a brain biopsy is often how these tumors of unknown origin are diagnosed.

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