Ependymomas span a wide spectrum, from essentially benign growths that can be cured with surgery alone to aggressive childhood brain tumors that carry a serious risk of death. Calling the entire group “benign” or “malignant” misses the point: the tumor’s molecular subtype, location, and the patient’s age all shape how dangerous it actually is. This is one of those diagnoses where the label on the pathology report tells you far less than you might expect.
Why There Is No Single Answer
Ependymomas grow from ependymal cells, which line the fluid-filled spaces inside the brain and spinal cord. They can appear almost anywhere along that lining, from deep inside the brain’s ventricles to the very bottom of the spinal canal. Clinically, they range from slow-growing subependymomas that are practically benign to aggressive childhood posterior fossa tumors that are often deadly.1PubMed Central. Updates in the classification of ependymal neoplasms: The 2021 WHO Classification and beyond That breadth is part of what makes the benign-versus-malignant question so hard to answer in one sentence.
The traditional WHO grading system divided ependymomas into three tiers: grade I (subependymoma and myxopapillary ependymoma), grade II (“classic” ependymoma), and grade III (anaplastic ependymoma). In theory, higher grades mean more aggressive behavior. In practice, however, the distinction between grade II and grade III has not reliably predicted outcomes across multiple studies, and the tumor’s anatomical location can confound the grade’s meaning entirely.2PubMed. Epidemiology, molecular classification and WHO grading of ependymoma A grade II ependymoma in the brain of a toddler and a grade II ependymoma in the spine of an adult are, for all practical purposes, different diseases.
The Clearly Benign End of the Spectrum
Subependymomas sit at the gentlest end. These are slow-growing, well-circumscribed tumors that arise from the ventricular wall and are often found incidentally on brain imaging done for other reasons.3PubMed Central. A Rare Case of Bilateral Lateral Ventricular Subependymomas With Complete Resection of the Residual Tumor via Flexible Neuroendoscopy 20 Years After Initial Surgery Many subependymomas are watched without any treatment at all. When surgery is performed, outcomes are generally excellent, and recurrence is uncommon.
Myxopapillary ependymomas, which typically grow at the base of the spinal cord, were also historically placed in the low-grade category. They tend to be slow-growing in adults and are frequently curable with complete surgical removal. Children with myxopapillary ependymomas, however, tell a different story: their tumors are more likely to appear in unusual locations outside the spinal cord, and a substantial fraction recur or spread after initial treatment.4PubMed. Myxopapillary ependymoma in children: a study of 11 cases and a comparison with the adult experience The 2021 WHO classification actually upgraded myxopapillary ependymomas from grade I to grade II, reflecting this understanding that they are not always as harmless as they were once thought to be.
The Clearly Aggressive End
At the opposite extreme, anaplastic ependymomas (grade III) show rapid cell division, tissue invasion, and a high likelihood of recurrence. These tumors disproportionately affect children. In a large database analysis, about a third of pediatric ependymomas showed anaplastic features, compared with roughly 6% of tumors in older adults.5PubMed Central. Comparison of epidemiology, treatments, and outcomes in pediatric versus adult ependymoma Children also had much higher rates of undifferentiated tumors and substantially higher all-cause mortality than adolescents or young adults.
Transformation from a lower grade to a higher one is documented but rare. In one reported case, a grade II ependymoma in a two-year-old child recurred aggressively a year later and was reclassified as grade III anaplastic ependymoma at the second operation.6PubMed Central. Malignant Transformation of Grade II Ependymoma in a 2-Year-Old Child: Case Report Late malignant transformation has also been reported in adults whose low-grade posterior fossa ependymomas were initially treated with complete removal and radiation, only to disseminate and upgrade decades later.7Neurosurgery – Cases and Reviews. Three-Level Anterior Cervical Corpectomy for Resection of Disseminated Posterior Fossa Ependymoma: Case Report and Review of the Literature These cases are uncommon, but they illustrate that the benign-to-malignant boundary is not fixed over a patient’s lifetime.
Molecular Subtypes Matter More Than the Microscope
The most consequential shift in understanding ependymomas over the past decade has been the move toward molecular classification. Tumors that look similar under a microscope can behave in drastically different ways depending on their underlying molecular biology. As of the 2021 WHO classification, ten distinct types of ependymal tumors are now recognized, many defined by DNA methylation profiling rather than microscopic appearance alone.1PubMed Central. Updates in the classification of ependymal neoplasms: The 2021 WHO Classification and beyond
The starkest illustration of this comes from the posterior fossa, the most common site for childhood ependymoma. Tumors here fall into two major molecular groups, commonly called PFA and PFB. PFA tumors strike younger children, are harder to completely remove, and carry a grim prognosis: five-year progression-free survival in one study was about 43%, dropping to 37% at ten years.8PubMed Central. Survival and functional outcomes of molecularly defined childhood posterior fossa ependymoma: Cure at a cost PFB tumors, by contrast, had no failures at all during the same follow-up period. In a separate analysis, PFA patients had a median progression-free survival of about 28 months and a 33% death rate, while all PFB patients were alive at a median follow-up of over nine years.9Neuro-Oncology. PATH-03. DIFFERENCES IN CLINICAL COURSE OF GROUP-A AND GROUP-B POSTERIOR FOSSA EPENDYMOMA (PFA, PFB) AS DEFINED BY H3K27ME3 IMMUNOHISTOCHEMICAL ANALYSIS Same location, same grade on a biopsy report, completely different diseases in practice.
Above the tentorium (the supratentorial compartment of the brain), the dominant molecular driver involves a gene fusion called ZFTA. These tumors tend to occur in children and young adults. A related fusion involving YAP exists in the classification scheme but turns out to be extremely rare; one large collaborative effort failed to identify a single YAP-fused case in over five years of profiling.10Neuro-Oncology Advances. A multi-institutional retrospective pooled outcome analysis of molecularly annotated pediatric supratentorial ZFTA-fused ependymoma The practical takeaway is that molecular testing after surgery is now essential for predicting how an ependymoma will behave. A grade alone does not give doctors or families enough information to plan treatment.
Where the Tumor Grows Changes Everything
Location alone accounts for much of the variation in outcomes. Most adult ependymomas grow in the spinal cord, while most childhood ependymomas grow inside the skull. This is not just a demographic curiosity: spinal ependymomas, particularly the classic grade II type, tend to be well-defined tumors that are amenable to complete surgical removal and have relatively favorable outcomes. Spinal tumors account for roughly two-thirds of ependymomas in adults but less than 10% in children.5PubMed Central. Comparison of epidemiology, treatments, and outcomes in pediatric versus adult ependymoma
People with neurofibromatosis type 2 (NF2), a genetic condition that predisposes to multiple nervous system tumors, develop spinal ependymomas at especially high rates. About three-quarters of NF2-associated ependymomas show identifiable mutations in the NF2 gene.11PubMed. Spinal ependymomas in neurofibromatosis Type 2: a retrospective analysis of 55 patients Despite the high tumor burden, these ependymomas generally follow an indolent course and can often be managed with observation or surgery alone.12PubMed. Neurofibromatosis-2 and spinal cord ependymomas: Report of two cases and review of the literature This is another example of how an ependymoma can technically be a tumor of the central nervous system yet behave more like a benign growth.
Intracranial ependymomas, especially those in the posterior fossa of young children, face tighter surgical constraints because of surrounding critical brain structures. Incomplete removal at that location is common and is a major driver of recurrence and poor outcomes.
Surgery Is the Most Important Treatment, and How Much Gets Removed Matters Enormously
Across the board, the most consistent predictor of long-term survival in ependymoma is the extent of surgical removal. For spinal ependymomas, patients who had a complete resection had estimated five-year progression-free survival of 85%, compared with 18% for those with incomplete removal.13PubMed Central. Clinical presentation and extent of resection impacts progression-free survival in spinal ependymomas A separate study of intramedullary grade II ependymomas found ten-year progression-free survival of about 77%, with extent of resection being the only significant risk factor for tumor progression.14PubMed Central. Long-Term Outcomes after Incomplete Resection of Intramedullary Grade II Ependymomas: Is Adjuvant Radiotherapy Justified? Grade III tumors and those with high cell-division markers carried significantly worse outcomes in another spinal ependymoma cohort.15PubMed. Outcomes after surgical resection of spinal ependymomas: extent of resection, imaging phenotype, and survival
Radiation therapy plays a supporting role, particularly in intracranial ependymomas where complete removal is difficult. Proton-beam radiation, which spares more surrounding tissue than conventional radiation, appears to offer comparable tumor control in children with localized ependymoma.16PubMed. Progression-free survival of children with localized ependymoma treated with intensity-modulated radiation therapy or proton-beam radiation therapy Chemotherapy, by contrast, has been largely disappointing. Lab studies have shown that standard chemotherapy drugs like cisplatin and ifosfamide have virtually no effect on ependymoma cells, and etoposide produces only a modest decrease in cell survival.17Translational Oncology. Overcoming Chemoresistance of Pediatric Ependymoma by Inhibition of STAT3 Signaling This chemoresistance is one of the reasons ependymoma has been slower to see survival improvements than some other brain tumors.
Recurrence Can Happen Late
One unsettling feature of ependymoma is the possibility of very late recurrence. Unlike many cancers where the five-year mark is treated as a meaningful milestone, ependymomas can come back a decade or two after initial treatment. One reported case involved spinal cord recurrences from an intracranial ependymoma 14 years after the original tumor was completely removed and irradiated.18PubMed Central. Multiple spinal cord recurrences of an intracranial ependymoma after 14 years In a series of pediatric spinal ependymomas followed over several decades, half of patients experienced recurrence, with some appearing more than 20 years after the first surgery.19World Neurosurgery. Outcome After Treatment of Spinal Ependymoma in Children and Adolescents: Long-Term Follow-up of a Single Consecutive Institutional Series of 33 Patients Treated Over Eight Decades
Ependymomas can also spread through the cerebrospinal fluid, though this is relatively uncommon. A review of spinal fluid samples from ependymoma patients found detectable tumor cells in about 17% overall, with a higher rate in children (about 21%) than adults (about 7%). The majority of positive results came from patients with anaplastic tumors.20PubMed. Cerebrospinal fluid cytology in patients with ependymoma: a bi-institutional retrospective study This capacity for dissemination is part of why long-term surveillance with periodic MRI is standard for most ependymoma patients, regardless of grade.
How Ependymomas Are Told Apart From Other Brain Tumors
Ependymomas can look similar to medulloblastomas and other posterior fossa tumors on initial imaging, and getting the diagnosis right matters because treatments differ. MRI characteristics help distinguish the two: on diffusion-weighted imaging, ependymomas tend to have significantly higher apparent diffusion coefficient (ADC) values than medulloblastomas, reflecting differences in cellularity. In one study, using a specific ADC threshold correctly identified the tumor type with about 89% accuracy in both directions.21Clinical Radiology. Differentiating between adult intracranial medulloblastoma and ependymoma using MRI A pediatric study found a similar pattern, with ADC thresholds achieving roughly 90% sensitivity and 93% specificity.22PubMed Central. Diagnostic Accuracy of MRI and CT Scan Features in Differentiation of Pediatric Ependymoma from Medulloblastoma Ultimately, tissue diagnosis under the microscope (and increasingly, molecular profiling) confirms what imaging suggests.
Life After Treatment
Even when an ependymoma is successfully treated, the aftermath can be substantial. For spinal ependymomas, a quality-of-life study found that patients scored well below population norms, with pain and physical limitations being the most affected areas. Patients with tumors inside the spinal cord itself (intramedullary) fared significantly worse than those whose tumors grew outside the cord, and patients with persistent neurological deficits after surgery reported markedly lower quality of life.23Scientific Reports. Quality of life and return to work and sports after spinal ependymoma resection Female patients reported significantly lower quality-of-life scores than male patients in this cohort, though the reasons for that gap are not fully understood.
For children treated for posterior fossa ependymoma, the picture is somewhat more encouraging with time. After radiation therapy, most survivors had mild or no detectable neurological impairment by five years, and the number of patients with severe deficits decreased over follow-up. The main exception was hearing loss, which could be significant enough to require hearing aids or other intervention.24PubMed Central. Evolution of Neurological Impairment in Pediatric Infratentorial Ependymoma Patients Mild residual issues like facial weakness, limited eye movement, or subtle limb coordination problems were common but generally did not interfere with daily life. Cognitive effects, particularly on reading ability, have also been flagged as a vulnerability in children treated with cranial radiation.25PubMed Central. A Prospective Study of Conformal Radiation Therapy for Pediatric Ependymoma
What Causes Ependymoma
The honest answer is that nobody knows for most cases. Unlike some brain tumors where environmental exposures or inherited mutations have been clearly linked, ependymoma etiology remains largely unexplained. A population-based study in Denmark performed full genome sequencing on children diagnosed with ependymoma over 20 years and examined hundreds of cancer-related genes for inherited mutations, but the field is still in early stages of identifying clear germline predisposition.26PubMed Central. Redefining germline predisposition in children with molecularly characterized ependymoma: a population-based 20-year cohort The exception, as noted earlier, is NF2-associated spinal ependymoma, which has a well-understood genetic basis. For the vast majority of patients, though, ependymoma appears to arise sporadically.
The lack of clear risk factors makes prevention impossible and early detection difficult. Most ependymomas are diagnosed when they cause symptoms from their location: headaches and vomiting from blocked cerebrospinal fluid flow in brain tumors, or back pain and neurological changes in spinal tumors. There is no screening test, and the disease is rare enough that routine screening would not make sense for the general population.
Where Research Is Heading
The molecular revolution in ependymoma classification has been essential for understanding why patients have such different outcomes, but it has not yet translated into targeted drug therapies the way it has for some other cancers. The development of molecular therapies is considered essential, particularly for tumors that cannot be completely removed without causing severe neurological damage.27PubMed Central. Molecular Classification and Therapeutic Targets in Ependymoma Researchers are looking at signaling pathways active in specific subtypes and exploring whether drugs targeting similar pathways in other cancers could be repurposed. The challenge is that ependymoma is rare, which makes large clinical trials difficult to organize, and the biological diversity of the disease means a single drug is unlikely to work across all subtypes. For now, the most meaningful advances in patient care have come from better risk stratification using molecular profiling, allowing doctors to tailor surveillance intensity and treatment aggressiveness to the specific biology of each patient’s tumor rather than relying on a grade that may or may not predict what happens next.