Primary brain tumors arise from the brain, spinal cord, and associated tissues - collectively known as the central nervous system - rather than originating from cancerous cells that travel from elsewhere in the body. Primary brain tumors are categorized as either benign (noncancerous) or malignant (cancerous).
Despite their typically slow growth, noncancerous primary brain tumors still can have devastating physical and emotional effects. Meningiomas, for example, can grow anywhere on the meninges and as a result can gravely affect areas of the brain needed for such functions as sight, hearing, touch, balance, memory, or judgment.
Researchers are investigating the causes of brain tumors. Among the areas of investigation are environmental factors, exposure to certain viruses, and the role of genes. For most patients, there generally is no obvious exposure or risk factor that can be linked to these tumors.
Primary brain tumors are most commonly categorized by their “histology” or by the type of cells from which they form. The Central Brain Tumor Registry reports the following distribution of primary brain tumors by their histology: 1
As this table indicates, the most common type of primary brain tumor is meningioma, the noncancerous tumor that arises from the abnormal growth of the cells that form the delicate outer covering of the brain, called the meninges.
Additionally, the Central Brain Tumor Registry reports the following distribution of primary brain tumors by a patient's age: 1
Further, it reports the following distribution of primary brain tumors by site: 1
For more information on the types of brain tumors, click on these links:
Today, more than 350,000 people are living with primary brain tumors.2 An estimated 43,800 new cases of primary non-malignant and malignant brain and central nervous system tumors were expected to be diagnosed in the United States in 2005.3
These numbers are likely to increase given new legislation passed in the United States (The Brain Rumor Cancer Registries Amendment Act H.R. 5204), which mandates that federal cancer data-collection processes include data on benign brain tumors. Until passage of this legislation, it was generally accepted that the incidence of primary brain tumors was almost certainly underreported as:
- Two percent of routine autopsies reveal undiagnosed primary brain tumors;
- Most states did not require physicians to report the incidence of noncancerous primary brain tumors to state or federal registries.
The adult human brain is about 2% of the total body weight.