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Information on Brain Tumors

What is a Brain Tumor?

The brain is a complex organ that controls movement, sensation, speech, thought, memory, emotion, consciousness, breathing, heart rate, body temperature and many other crucial functions.  A brain tumor is a mass of abnormal cells in the brain that can interfere with its normal functioning.

Primary versus Metastatic Brain Tumors:

Brain tumors are either “primary” or “metastatic”. Primary brain tumors originate from cells in the brain and rarely spread to other parts of the body. Metastatic brain tumors originate from cells in other organs and then metastasize (spread) to the brain.

Benign versus Malignant Brain Tumors:

Primary brain tumors are categorized as benign (non-cancerous) or malignant (cancerous) and assigned a grade based on the aggressiveness of the tumor.  The World Health Organization grading system is used at the University of Colorado as well as most other institutions to assign a grade of I to IV to primary brain tumors. Grading is based on how quickly the tumor cells are dividing, how abnormal the tumors cells look under a microscope, the extent of invasion of the cells into normal brain tissue, the likelihood of the tumor becoming a higher grade, and other features. All metastatic brain tumors are considered malignant based on the fact that they have spread from one organ to another. Metastatic brain tumors are assigned a grade according to the accepted grading system for the organ in which they started.

Cause of Brain Tumors:

Brain tumors are presumed to occur due to alterations in the genetic material of normal cells, causing them to develop and divide abnormally. The vast majority of brain tumors are not thought to be caused by inherited genetic changes (ie do not “run in families”), although there are rare genetic syndromes that result in increased risks for brain tumors. The source of the genetic alterations is generally unknown, but our researchers and others are actively exploring potential causes.  

Symptoms of Brain Tumors:

Symptoms of brain tumors depend on the location and size of the tumor, as well as how quickly the tumor is growing. Symptoms can be due to pressure on specific areas of the brain by the tumor itself or to pressure on the entire brain from swelling or hydrocephalus. Hydrocephalus is an abnormal accumulation of the fluid (cerebrospinal fluid) that normally flows around the brain and spinal cord. Occasionally a brain tumor will be discovered incidentally during an evaluation for an unrelated health problem in a person with no symptoms.  

The most common symptoms of brain tumors are one or more of the following:

Nausea and vomiting
Changes in thinking or memory
Changes in behavior
Problems with vision, hearing, or speech
Weakness in the arms or legs
Numbness or tingling
Difficulty walking due to trouble with balance or coordination

Types of Brain Tumors:

To learn more about a specific type of brain tumor, please select one of the links below: