OHSU

About Brain and Central Nervous System Tumors

What Is a Brain Tumor?

 A brain tumor is an abnormal growth of tissue in the brain. The tumor can start in the brain (primary brain tumor) or start in another part of the body and spread to the brain (secondary tumor, also called a metastatic tumor).

Brain tumors are classified as benign (non-cancerous) or malignant (cancerous), depending on:

  • How they grow and change
  • If they come back after being removed

A benign (non-cancerous) tumor does not contain cancer cells. If it is removed with surgery, it usually does not recur (come back). Most benign brain tumors have clear borders. This means the tumor tissue does not spread to healthy tissue nearby.

Even though they aren't cancerous, benign tumors can cause symptoms by pressing on parts of the brain. Symptoms depend on the tumor's size and where it is located in the brain.

Malignant brain tumors contain cancer cells. They are usually fast growing and spread to nearby healthy tissue. Malignant brain tumors very rarely spread to other areas of the body, but may recur (come back) after treatment. Benign (non- cancerous) brain tumors are sometimes called malignant if they damage the brain because of their size or location.

Metastatic brain tumors are tumors that start in another part of the body. The tumor cells spread to the brain through the lymph system and bloodstream.

Cancers that commonly travel to the brain include:

  • Lung cancer
  • Breast cancer
  • Nasopharyngeal cancer
  • Melanoma (a type of skin cancer)
  • Colon cancer

Doctors describe and treat these cancers based on their specific type. For example, breast cancer that spreads to the brain is still called breast cancer.

What Causes Brain Tumors?

Most brain tumors have abnormal genes that allow cells to grow out of control. The genes are abnormal because something, such as an inherited condition or environmental factor, changed the way they work.

If you have certain genetic (inherited) medical conditions, you have a higher risk of brain or central nervous system tumors. These conditions include:

  • Neurofibromatosis
  • Von Hippel-Lindau disease
  • Li-Fraumeni syndrome
  • Retinoblastoma

There are also reports of people in the same family developing brain tumors without any of these genetic conditions.

People who do certain jobs may get brain and central nervous system tumors more often, though not all studies agree. These jobs include:

  • Oil refining
  • Rubber manufacturing
  • Chemical industries (chemists)

Doctors don't yet know if chemicals used in these jobs cause brain or central nervous system tumors.

If you had radiation therapy to your head for another medical condition, this can raise your brain tumor risk.


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