Ependymomas are glial cell tumors that commonly arise in the lining cells of the ventricular system, and less commonly outside the central nervous system (CNS), or within the brain parenchyma. They are comprised of genetically distinct subgroups of tumors and affect children more commonly than adults.
While ependymomas that arise from different regions of the CNS are histologically similar, their clinical course often varies. Histological classification alone has not provided consistent and reliable survival outcomes in retrospective studies, meaning that ependymomas with similar histological grade may follow a substantially different clinical course. Recent studies suggest that these tumors may be categorized based on different populations of progenitor cells, which would explain different clinical courses in tumors with the same histological grade. Several genetic abnormalities have been found to correlate with ependymoma and comprise large genomic regions. Some of these studies have demonstrated that ependymomas correlate with distinct oncogenic products and molecular subgroups which may correlate more accurately with clinical outcomes compared with than histologic classification alone.
As per the Central Brain Tumor Registry of the United States (CBTRUS) Statistical Report for CNS tumors from the years 2011 to 2015, ependymal tumors represent 1.7% of all brain and CNS tumors, with a median age of 44 years.
In childhood, brain tumors are the primary cause of death associated with solid tumors. The most common pediatric brain tumors being medulloblastoma, pilocytic astrocytoma, brainstem glioma, and ependymoma.
As with other CNS tumors, the TNM system of classification does not apply to ependymomas as they rarely spread outside of the CNS, and the WHO classification for CNS tumors is the current standard used to classify these ependymomas:
As ependymomas arise within different CNS compartments, their clinical presentation may vary from acute onset increased intracranial pressure causing nausea and vomiting, to a more chronic and insidious clinical course.
Ependymoma is a histological diagnosis, and it most commonly presents in three major anatomical sites: supratentorial, spinal cord and infratentorial.
Ependymoma is commonly suspected in adult patients suffering prolonged clinical courses, who present a non-enhancing and well-demarcated intraventricular lesion on brain imaging, isodense in computed tomography, and isointense on T1 images on MRI.
Traditionally, ependymomas are classified using the World Health Organization (WHO) system to classify tumors of the nervous system. This histological grading commonly aids in predicting the clinical and biological behavior of central nervous tumors. In ependymoma, however, the molecular and genomic profile may provide more accurate information than only using histological grade.
Tumor grading using the WHO classification system for nervous system tumors is based on different histological grades, this classification by itself would often not provide a reliable estimate of clinical course in patients with ependymoma. With increasing information about molecular pathogenetic mechanisms in ependymomas, the 2016 classification for nervous system tumors from WHO now includes in their classification the presence or absence of specific genetic alterations, RELA fusion-positive or negative, for ependymomas.
There are nine molecular subgroups described in ependymomas, which correlate with different anatomical locations, genetics, and demographic characteristics. These new findings offer the opportunity of potentially improving the classification, management and prognostic information for ependymomas based on their molecular subgroup.
No current molecular or immunohistochemical markers are in routine use in the diagnostic workup for patients with ependymoma.
Ependymal tumors are rare, constituting 1.7% of all brain tumors, as reported in the most recent CBTRUS statistical report; this poses a challenge in defining the optimal management for these entities. Retrospective studies have described improved survival in patients undergoing resection with adjuvant radiation therapy. There is minimal and limited evidence supporting chemotherapy for adult ependymomas.
No established guidelines use the molecular subgroups to guide treatment of ependymoma. The current consensus, however, recommends that patients with PF-EPN-A positive ependymoma, who are older than 12 months of age, undergo maximal safe micro-neurosurgical removal in addition to local radiotherapy.
For intracranial ependymomas, surgery is typically the mainstay treatment. Complete resection without residual disease has presented better clinical outcomes and overall survival than partial resection. As discussed previously, there is insufficient evidence to support the use of chemotherapy.
Differential diagnosis for tumors in the posterior fossa includes, astrocytoma, medulloblastoma, choroid plexus tumors. For supratentorial tumors, differential includes glial tumors, choroid plexus carcinoma or papilloma, and embryonal tumors.
The extent of surgical resection for intracranial ependymomas has been the most reliable and consistent independent prognostic factor. Intracranial ependymomas show a low metastatic potential and predominantly present a locally invasive histological pattern. Ependymomas that fall within the histological grade III from the WHO classification have correlated with a worse outcome than grade II.
Patients who undergo complete resection without signs of residual disease have presented a better outcome and overall survival compared to patients who undergo partial resection. For this reason, treatment typically consists of aggressive surgical excision.
Across the different subgroups, infratentorial ependymomas generally have an excellent prognosis, even without treatment. Supratentorial ependymomas, however, often present a higher histological grade and have a lower survival rate despite treatment with resection and adjuvant radiation.
Prognosis varies for pediatric patients and will be subject to location, type of treatment and pathological classification. A previous study showed that gross total resection had the best overall and progression-free survival. Patients with WHO classification grade II had improved overall survival after gross total resection in addition to external beam radiation therapy, and improved progression-free survival after gross total resection alone. Patients with WHO classification grade III had improved overall survival after subtotal resection in addition to external beam radiation therapy. While progression-free survival was better in patients with infratentorial tumors following subtotal resection in addition to external beam radiation therapy.
Patients who are long term survivals from CNS tumors may present a wide diversity of complications, including neurological deficits, cognitive limitations, sensorineural hearing loss, endocrine and growth abnormalities, and secondary malignancies. Adult patients may present long term complications, most commonly fatigue, numbness and tingling, pain, and disturbed sleep.
Patients should receive counseling regarding their prognosis. Those with CNS tumors at end-of-life benefit from palliative care. Family members and patients will benefit from early and anticipatory counseling, in addition to comfort measures. Palliative care should be interdisciplinary to cover for the wide spectrum of needs that these patients will face.
The mainstay of treatment for ependymoma includes an interprofessional approach that may include surgery, radiation therapy, and chemotherapy. For confirmation of the tumor through tissue biopsy or tumor resection therapy, referral to neurosurgery is necessary. Palliative care may be necessary for patients at end-of-life. Those who undergo surgery may also develop a number of neurological deficits. These individuals may require physical therapy, speech therapy, and occupational therapy. In many cases, the neurological deficits are permanent.
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