A brain tumor is a collection, or mass, of abnormal cells in your brain. Your skull, which encloses your brain, is very rigid. Any growth inside such a restricted space can cause problems. Brain tumors can be cancerous (malignant) or noncancerous (benign). When benign or malignant tumors grow, they can cause the pressure inside your skull to increase. This can cause brain damage, and it can be life-threatening.
Brain tumors are categorized as primary or secondary. A primary brain tumor originates in your brain. Many primary brain tumors are benign. A secondary brain tumor, also known as a metastatic brain tumor, occurs when cancer cells spread to your brain from another organ, such as your lung or breast.
Types of brain tumors
Primary brain tumors
Primary brain tumors originate in your brain. They can develop from your:
brain cells
the membranes that surround your brain, which are called meninges
nerve cells
glands
Primary tumors can be benign or cancerous. In adults, the most common types of brain tumors are gliomas and meningiomas.
Gliomas
Gliomas are tumors that develop from glial cells. These cells normally:
support the structure of your central nervous system
provide nutrition to your central nervous system
clean cellular waste
break down dead neurons
Gliomas can develop from different types of glial cells.
The types of tumors that begin in glial cells are:
astrocytic tumors such as astrocytomas, which originate in the cerebrum
oligodendroglial tumors, which are often found in the frontal temporal lobes
glioblastomas, which originate in the supportive brain tissue and are the most aggressive type
Other primary brain tumors
Other primary brain tumors include:
pituitary tumors, which are usually benign
pineal gland tumors, which can be benign or malignant
ependymomas, which are usually benign
craniopharyngiomas, which occur mostly in children and are benign but can have clinical symptoms like changes in vision and premature puberty
primary central nervous system (CNS) lymphomas, which are malignant
primary germ cell tumors of the brain, which can be benign or malignant
meningiomas, which originate in the meninges
schwannomas, which originate in cells that produce the protective cover of your nerves (myelin sheath) called Schwann cells
Most meningiomas and schwannomas occur in people between the ages of 40 and 70. Meningiomas are more common in women than men. Schwannomas occur equally in both men and women. These tumors are usually benign, but they can cause complications because of their size and location. Cancerous meningiomas and schwannomas are rare but can be very aggressive.
Secondary brain tumors
Secondary brain tumors make up the majority of brain cancers. They start in one part of the body and spread, or metastasize, to the brain. The following can metastasize to the brain:
lung cancer
breast cancer
kidney cancer
skin cancer
Secondary brain tumors are always malignant. Benign tumors don’t spread from one part of your body to another.
What are the risk factors for a brain tumor?
Risk factors for brain tumors include:
Family history
Only about 5 to 10 percent of all cancers are genetically inherited, or hereditary. It’s rare for a brain tumor to be genetically inherited. Talk to your doctor if several people in your family have been diagnosed with a brain tumor. Your doctor can recommend a genetic counselor for you.
Age
Risk for most types of brain tumors increases with age.
Race
Brain tumors in general are more common among Caucasians. However, African-American people are more likely to get meningiomas.
People who have been exposed to ionizing radiation have an increased risk of brain tumors. You can be exposed to ionizing radiation through high-radiation cancer therapies. You can also be exposed to radiation from nuclear fallout. The nuclear power plant incidents in Fukushima and Chernobyl are examples of how people can be exposed to ionizing radiation.
