Brain Tumor Education

What is a Brain Tumor?

A brain tumor is a growth of abnormal cells that have formed in the brain. Some brain tumors are cancerous (malignant), while others are not (non-malignant). Either way, tumors in the brain or central nervous system. The central nervous system is made up of the brain as well as the spinal cord. It can affect the brain’s ability to work normally.

What is the difference between malignant and benign brain tumors?

Whether a tumor is benign or malignant depends on the level of cell abnormality. If the tumor is made up of normal looking cells, then it is benign; however, if the cells are abnormal, then the tumor is malignant.

“Benign” brain tumors are not cancer, although they often cause symptoms and will sometimes require treatment. Although many people are familiar with the term “benign,” it’s not always an accurate description. Even a so-called “benign” tumor is a serious medical condition. For that reason, we prefer to use the term “non-malignant” to describe brain tumors made up of noncancerous cells.

Malignant brain tumors are cancer. They generally grow faster and more aggressively than non-malignant tumors, invade other areas of the brain and spinal cord, and can be deadly.

Are All Brain Tumors Brain Cancer?

No. In fact, most brain tumors are not cancerous. Less than one-third of brain tumors are cancerous (malignant).

What is Tumor Grading?

A tumor grade is a way to classify a tumor and will help members of the healthcare team communicate more clearly about the tumor, determine treatment options, and predict outcomes.

Tumors are assigned Grade I, II, III, or IV based on abnormalities of the cells they contain. A tumor can have more than one grade of cell. The highest, or most malignant, grade of cell determines the tumor’s grade, even if most of the tumor is made up of lower-grade cells.

World Health Organization (WHO) Tumor Grade Descriptions

Grade I: These are the least malignant tumors and are usually associated with long-term survival. They grow slowly and have an almost normal appearance when viewed through a microscope.

Grade II: These tumors are slow growing and look slightly abnormal under a microscope. Some can spread into nearby normal tissue and recur, sometimes as a higher grade tumor.

Grade III: These tumors are malignant, although there is not always a significant difference between grade II and grade III tumors. The cells of a grade III tumor are actively reproducing abnormal cells, which grow into nearby normal brain tissue. These tumors tend to recur, often as a grade IV.

Grade IV: These are the most malignant tumors. They reproduce rapidly, can have a bizarre appearance when viewed under the microscope, and easily grow into nearby normal brain tissue. These tumors form new blood vessels so they can maintain their rapid growth.

Overview of the Brain’s Anatomy

The central nervous system (CNS) is made up of the brain and spinal cord. The brain is the most critical organ in the body. It directs and regulates all body functions.

The brain is made up of multiple parts, and each part of the brain is responsible for a different body function. Therefore, brain tumor symptoms, and potential treatment options, depend a great deal on where the tumor is located.

Brain Tumor Statistics

Brain tumors do not discriminate. They affect all ages, genders, and ethnicities. Information source (unless otherwise specified): Central Brain Tumor of the United States Annual Report (1).

  • Over 700,000 Americans are living with a brain tumor today (2).
  • More than 84,000 people will be diagnosed with a primary brain tumor in 2021.
  • There are more than 120 different types of primary brain and CNS tumors.
  • Nearly one-third (29.7 percent) of brain and central nervous system (CNS) tumors are malignant.
  • More than 28,000 kids in the United States are fighting brain tumors right now (2).
  • This year, approximately 18,000 people will die as a result of a primary malignant brain tumor (3).
  • Survival after diagnosis with a primary brain tumor varies significantly by age, geographical location, tumor type, tumor location, and molecular markers.

Brain Tumor Statistics by Age

  • The median age at diagnosis for all primary brain tumors is 60 years.
  • From 2013-2017, brain tumors were the most common cancer among children 0-14. They were the leading cause of cancer-related deaths in this age group.
  • About 3,400 children will be diagnosed with a primary brain tumor in 2021.
  • From 2013-2017, malignant brain tumors were the 3rd most common cancer among those age 15-39 .
  • More than 4,600 children and adolescents between the ages of 0-19 will be diagnosed with a primary brain tumor in 2021.
  • About 11,700 adolescents and young adults will be diagnosed with a primary brain tumor in 2021.
  • From 2013-2017, brain tumors were the 8th most common cancer among persons age 40+, and the 3rd most common cause of cancer death.


  1. Ostrom QT, Patil N, Cioffi G, Waite K, Kruchko C, Barnholtz-Sloan JS. CBTRUS Statistical Report: Primary Brain and Other Central Nervous System Tumors Diagnosed in the United States in 2013–2017. Neuro Oncol. 2020.
  2. Porter KR, McCarthy BJ, Freels S,Kim Y, Davis FG. Prevalence estimates for primary brain tumors in the United States by age, gender, behavior, and histology. Neuro-Oncology 12(6):520-527, 2010.
  3. Siegel RL, Miller KD, Jemal A. Cancer statistics, 2020. CA Cancer J Clin. 2020 Jan;70(1):7-30. doi: 10.3322/caac.21590. Epub 2020 Jan 8. PubMed PMID: 31912902.

Risk Factors for Brain Tumors

Risk factors are things that may increase a person’s chance of getting a disease. Some risk factors, like age, genetics, and family history, are out of our control. Other risk factors, like smoking, are within our power to change.

Most of the time, we don’t know what causes a given person to develop a brain tumor. Having one or more risk factors does not automatically mean that you’ll develop a brain tumor, just as the lack of risk factors doesn’t guarantee that you’ll never develop one. Talk with your doctor about what you can do to reduce your risk.

Environmental Risk Factors

Of the many potential risk factors scientists have studied, only one – exposure to ionizing radiation – has been clearly shown to increase the risk of developing brain tumors. Ionizing radiation is frequently found in X-rays, which is why human bodies are protected by lead shields when some X-rays are performed.

Genetic Risk Factors

Anything that refers to the genes can be called “genetic.” However, only about 5 to 10 percent of brain tumors are passed down from one generation to another in a family (heredity).

In cases of hereditary brain tumors, a mutation change in the DNA sequence that makes up a specific gene is passed from parent to child. Most genetic risk factors are not present at birth, but actually develop as we age. While most of our genes do their jobs as expected, a small number develop a mutation or other error that causes them stop working the way they should. This malfunctioning can change the way cells grow, which may eventually lead to the development of cancer.

If multiple members of your family have been diagnosed with brain tumors, or you have concerns about starting a family, a genetic counselor may be able to help. Contact the National Cancer Institute’s Cancer Information Service (1-800-422-6237) to find a genetic counselor in your area.