An ependymoma is a type of primary tumor that originates in the brain or spine, which together are referred to as the central nervous system (CNS). Ependymomas grow from ependymal cells, which line the fluid spaces of the brain. These cells produce and regulate cerebrospinal fluid (CSF) production in the brain.
Some other kinds of gliomas include the most common glial tumor, the astrocytoma (which grows from the star-shaped cells known as astrocytes), and oligodendrogliomas (which are named for oligodendrocyte cells, which they resemble).
Ependymoma tumors are rare and account for only two percent of central nervous system tumors in adults. Most ependymoma tumors in adults are slow-glowing and considered benign, and they rarely spread outside the central nervous system. However, some types can metastasize through the cerebrospinal fluid to different areas of the brain and spine.
Most ependymomas in adults are found in the spine, where they can occur at every level, including the cervical (neck), thoracic (upper back), lumbar (lower back), and lower lumbar and sacral regions (base of the spine, above the tailbone). However, they can and do occur in the brain in both adults and children.
Types of Ependymomas
Like other kinds of tumors, an ependymoma is classified according to a system developed by the World Health Organization. This system standardizes communication about tumors and is important for treatment planning and determining an individual’s prognosis. A spine or brain tumor is assigned this grade based on its characteristics, such as its cell type (where it originated), how fast it is growing, and how closely it resembles normal cells. A neuropathologist may make this assessment based on an examination of cells taken during a biopsy by a neurosurgeon.
Differentiated and anaplastic are terms used to describe how similar or abnormal the tumor cells appear compared to normal cells. A well-differentiated tumor cell looks very much like a normal, healthy cell; an anaplastic cell is poorly differentiated and shows little similarity to the original cell.
The words supratentorial and infratentorial are used to refer to the location of the ependymomas within the brain; the word tentorial comes from the word tentorium, which is a thick membrane that separates the cerebrum (top two-thirds of the brain) from the cerebellum (bottom third). Supratentorial ependymomas occur above the tentorium; this area includes the lateral and third ventricles (fluid-filled spaces in the brain that produce cerebrospinal fluid) as well as the cerebral hemispheres. Infratentorial are found below the tentorium in the area of the brain known as the posterior fossa, which includes the fourth ventricle, the brain stem, and the cerebellum. Infratentorial tumors are more likely to spread to the spine than supratentorial tumors.
Grade I ependymoma tumors are generally the slowest growing and include the following subtypes:
Grade II ependymoma tumors are the most common ependymomas and are considered low grade. A grade II ependymoma grows in a ventricle in the brain or in the spinal cord. Subtypes include:
Some grade II ependymoma tumors may recur as a higher grade tumor following treatment.
Grade III ependymomas tumors are known as anaplastic ependymomas. Anaplastic is a term used to describe cancer cells that divide rapidly, typically faster than other grades, and have little or no resemblance to normal cells. Usually found in the skull, brain, and brain stem and only rarely in the spine, anaplastic ependymomas are malignant, grow quickly, and spread into other parts of the brain through the cerebrospinal fluid. Grade III ependymoma tumors tend to recur after treatment. (Find out more about our Neuro-oncology service.)
What Causes an Ependymoma?
The cause of most ependymoma tumors is unknown. It rarely occurs in members of the same family, although people with a genetic disorder called neurofibromatosis type II have a higher risk of developing an ependymoma.
Researchers are making progress, but they often can’t pinpoint what causes the genetic mutations that lead to spine or brain tumors. Some tumors may arise from genetic mutations linked to exposure to environmental toxins or from previous radiation treatments for other cancers.
Although scientists do not yet fully understand the cause of ependymomas, brain and spine tumors are the subjects of intense research and investigation. Find out more about brain tumor research at the Weill Cornell Medicine Brain and Spine Center.
Reviewed by: Rohan Ramakrishna, MD
Last reviewed/last updated: December 2020
Illustration by Thom Graves, CMI