Ependymoma: Understanding Your Pathology Report

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Ependymoma is a tumor that grows from ependymal cells. These cells line the fluid-filled spaces of the brain and the narrow central canal running down the middle of the spinal cord. Ependymomas can develop anywhere along that lining, from the top of the brain to the bottom of the spine where the tumor starts matters more than almost anything else.

This article is an overview of the whole group. It explains what ependymal cells are, what all ependymomas share under the microscope, and how the type is decided. Because the different types behave so differently, each has its own detailed article, and this page will point you to the one that matches your report.

What are ependymal cells?

The brain contains four connected fluid-filled spaces called ventricles, and a narrow channel called the central canal runs down the middle of the spinal cord. A single layer of ependymal cells lines both. Their job is to help move and regulate the cerebrospinal fluid that cushions the brain and spinal cord.

Ependymal cells belong to a wider family called glial cells, the nervous system’s support cells. This is why an ependymoma may be described in your report as a glial tumor, or glioma, and why the tumor cells carry proteins shared with other glial tumors.

Where do ependymomas occur, and who gets them?

Ependymomas make up roughly 5 to 10 percent of brain and spinal cord tumors in children, where they are among the most common. They make up a smaller share of these tumors in adults. Age strongly influences where the tumor appears, and this is the first thing that separates one patient’s situation from another’s.

In children. Most ependymomas are inside the skull, and most of those are in the posterior fossa, the lower back part of the brain. Children under 3 are the group most often affected.
In adults. Most ependymomas are in the spinal cord rather than the brain. Spinal ependymoma is the commonest tumor arising within the adult spinal cord.
At any age. Myxopapillary ependymoma forms at the very bottom of the spinal cord and occurs in both children and adults.

What are the symptoms of an ependymoma?

The symptoms of an ependymoma come from where it sits rather than from the tumor itself. They therefore differ completely between a tumor in the brain and one in the spine.

Tumors inside the skull block the flow of cerebrospinal fluid, which raises the pressure inside the head. This can cause headaches that are often worse in the morning, nausea and vomiting, unsteadiness, and double vision. In babies, whose skulls can still expand, it can show as faster-than-expected head growth, a bulging soft spot, irritability, and sleepiness.

Spinal cord tumors press on the nerve pathways running through it. This can cause back or neck pain, weakness, numbness or tingling in the arms or legs, difficulty walking, and changes in bladder or bowel control. Symptoms usually build gradually over months.

How is the diagnosis made?

Diagnosing an ependymoma takes three kinds of information, and the modern pathology report brings them together into an integrated diagnosis.

MRI comes first and shows where the tumor is, how large it is, and what it is pressing on. A pathologist then confirms the diagnosis by examining the tissue. The tissue usually comes from surgery to remove as much of the tumor as safely possible, and sometimes from a biopsy. Finally, molecular tests examine the tumor’s genetic material and assign it to a specific type.

Ependymomas can spread through the cerebrospinal fluid to other parts of the brain and spine. An MRI of the whole spine, and sometimes a fluid sample, is therefore part of the initial assessment. This does not mean spread is expected. It is standard practice to understand the full picture before planning treatment.

What does an ependymoma look like under the microscope?

All ependymomas share a family resemblance under the microscope, regardless of location, and pathologists look for two patterns.

Perivascular pseudorosettes. Tumor cells arranged in a ring around a blood vessel, with a clear zone of fine fibers between the cells and the vessel. This is the most characteristic feature of ependymoma and is present in nearly all cases.
Ependymal rosettes. Tumor cells forming a ring around a small space, recreating the channel that ependymal cells normally line. These are less common but, when present, are strong evidence of an ependymoma.

The tumor cells are usually small and fairly uniform, with round or oval nuclei, set in a fibrillary background, meaning it contains fine, hair-like fibers. The report may also describe mitotic figures (dividing cells) and microvascular proliferation (new small blood vessels forming within the tumor). It may describe necrosis, meaning dead tumor tissue. These features contribute to the grade.

Immunohistochemistry

Immunohistochemistry uses antibodies to detect specific proteins inside the tumor cells, and the pattern of results confirms that a tumor is an ependymoma rather than something that resembles one.

Ependymomas are typically positive for GFAP, a protein found in glial cells, which confirms the tumor’s glial origin. They also show a distinctive pattern with a stain called EMA, which appears as tiny dots or small rings inside the cells rather than as general staining. That dot-like pattern is close to a signature for this tumor family. Ependymomas are usually negative for OLIG2, which helps separate them from astrocytomas, another glial tumor that can look similar.

Further stains depend on where the tumor is, and those are covered in the specific articles below.

The types of ependymoma

This is the part of an ependymoma report that matters most. The World Health Organization classification of central nervous system tumors, 5th edition, was published in 2021. It defines the types of ependymoma by where the tumor is and what molecular changes it carries. Two tumors that look identical under the microscope can be different diseases with different outlooks.

Find the one that matches your report.

Posterior fossa ependymoma. In the lower back part of the brain; the most common site in children. Divided into group A and group B, which are separated by a stain called H3K27me3 and by DNA methylation profiling. Group matters more than trade.
Supratentorial ependymoma. In the upper part of the brain. Defined by a fusion gene involving either ZFTA or YAP1, and the two behave differently.
Spinal cord ependymoma. Within the spinal cord itself, and the commonest form in adults. Most involve the NF2 gene and loss of chromosome 22. A small number carry MYCN amplification, which substantially changes the outlook.
Myxopapillary ependymoma. At the very bottom of the spinal canal, in the conus medullaris and filum terminale. Distinctive under the microscope, with jelly-like material around the blood vessels, and now classified as WHO grade 2.
Subependymoma. A slow-growing WHO grade 1 tumor found mainly in adults, often discovered by chance on a scan done for another reason. It is the most favorable member of the family.

If your report gives a location but no molecular group, testing may still be in progress, or there may not have been enough tissue. Reports sometimes add the abbreviation NOS, meaning molecular testing could not be done, or NEC, meaning it was done but the result did not match any recognized group. Neither changes the diagnosis of ependymoma itself.

What does the WHO grade mean?

Every ependymoma is given a CNS WHO grade, from 1 to 3, based on how the cells look and how quickly they are dividing. Grade 1 covers subependymoma. Most other ependymomas are grade 2 or grade 3, with grade 3 assigned when there are many dividing cells, new small blood vessels, or dead tumor tissue.

The grade is on the report because it is part of the official classification. It is worth understanding that it carries less weight here than in many other tumors. Studies have repeatedly shown that WHO grade alone does not reliably predict how an ependymoma will behave. Molecular type, location, and how completely the tumor was removed are stronger predictors. This is why modern reports present the grade alongside the molecular findings rather than on its own.

What is the prognosis?

Outlook in ependymoma varies more widely than in most tumor types, so a single number for the whole group would be misleading. Three things drive it.

How completely the tumor was removed—the strongest factor across every type, and often the one that most influences what treatment follows. Complete removal is associated with substantially better outcomes across the board
The molecular type. Some types are associated with a high chance of long-term control, while others return more often. Each article explains this in more detail.
Location and age. Spinal and myxopapillary ependymomas generally do well, with long-term survival above 90 percent in many series. Tumors inside the skull, particularly in very young children, carry a higher risk of returning.

One feature is shared across the group. Ependymomas can return many years after treatment, sometimes a decade or more later, so MRI follow-up continues long after treatment ends. That is not a sign that anything has gone wrong. It is how this family of tumors is properly monitored.

What happens after the diagnosis?

A team plans care, including a neurosurgeon, a neuro-oncologist, a radiation oncologist, and a neuropathologist. Because molecular testing is central to the diagnosis, the full report can take longer than families expect, and treatment decisions may wait for it.

Surgery is the mainstay of treatment for every type of ependymoma, and removing as much tumor as can safely be taken is the goal. Where tumor remains, a second operation is sometimes planned, occasionally after other treatment has been given. Radiation is used for most tumors inside the skull and for some spinal tumors. A child’s age is weighed carefully in that decision, since radiation to the developing brain carries long-term costs. Chemotherapy has a more limited role and is used mainly in infants, where it can delay radiation until the brain is more developed.

Long-term follow-up covers both the tumor and treatment effects, including learning, hormone function, hearing, and, for spinal tumors, strength and bladder function.

Questions to ask your doctor

Where exactly is my ependymoma, and which type does the report say it is?
Was a molecular group or fusion identified, and which tests were used?
If the report says NOS or NEC, can further testing still be done?
What CNS WHO grade is listed, and how much weight does it carry in my case?
Was the whole tumor removed, and was an MRI done afterward to confirm?
If tumor remains, is a second operation being considered?
Was the rest of my spine imaged, and was the cerebrospinal fluid examined?
Is radiation being recommended, and how was my age weighed in that decision?
Would chemotherapy be used, and if so, for what?
How often will I need follow-up MRI scans, and for how many years?
What would happen if the tumor came back?
Is treatment being given on a clinical trial or a standard protocol?
Has a pathologist who specializes in nervous system tumors reviewed the slides?