What are primary brain tumors?
Tumors that begin in brain tissue are known as primary tumors of the brain. (Information about secondary brain tumors appears in the following section.) Primary brain tumors are named according to the type of cells or the part of the brain in which they begin.
The most common primary brain tumors are gliomas. They begin in glial cells. There are many types of gliomas:
The tumor arises from star-shaped glial cells called astrocytes. In adults, astrocytomas most often arise in the cerebrum. In children, they occur in the brain stem, the cerebrum, and the cerebellum. A grade III astrocytoma is sometimes called an anaplastic astrocytoma. A grade IV astrocytoma is usually called a glioblastoma multiforme.
Brain stem glioma –
The tumor occurs in the lowest part of the brain. Brain stem gliomas most often are diagnosed in young children and middle-aged adults.
The tumor arises from cells that line the ventricles or the central canal of the spinal cord. They are most commonly found in children and young adults.
This rare tumor arises from cells that make the fatty substance that covers and protects nerves. These tumors usually occur in the cerebrum. They grow slowly and usually do not spread into surrounding brain tissue. They are most common in middle-aged adults.
Some types of brain tumors do not begin in glial cells. The most common of these are:
- Medulloblastoma – This tumor usually arises in the cerebellum. It is the most common brain tumor in children. It is sometimes called a primitive neuroectodermal tumor.
- Meningioma – This tumor arises in the meninges. It usually grows slowly.
- Schwannoma – A tumor that arises from a Schwann cell. These cells line the nerve that controls balance and hearing. This nerve is in the inner ear. The tumor is also called an acoustic neuroma. It occurs most often in adults.
- Craniopharyngioma – The tumor grows at the base of the brain, near the pituitary gland. This type of tumor most often occurs in children.
- Germ cell tumor of the brain – The tumor arises from a germ cell. Most germ cell tumors that arise in the brain occur in people younger than 30. The most common type of germ cell tumor of the brain is a germinoma.
- Pineal region tumor – This rare brain tumor arises in or near the pineal gland. The pineal gland is located between the cerebrum and the cerebellum.