Anaplastic ependymoma
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Definition
Anaplastic ependymoma is a malignant glioma of ependymal origin. These lesions exhibit high mitotic activity, often accompanied by microvascular proliferation and pseudopalisading necrosis. Anaplastic ependymoma corresponds to WHO Grade III glioma.
Epidemiology/ Localization
Incident data vary considerably due to variations in histological criteria for diagnosis, but anaplastic changes appear to be more common in intrancranial ependymomas, particular those in the posterior fossa.
Clinical presentation
Signs and symptoms are similar to those for ependymoma, but tend to arise less insidiously.
Imaging
On MRI, anaplastic ependymomas have a similar appearance to that of ependymomas, but may demonstrate evidence of invasion of the surrounding brain parenchyma.
Macroscopy
Anaplastic ependymomas have a similar macroscopic appearance to that of ependymomas, but may demonstrate evidence of invasion of the surrounding brain parenchyma.
Histopathology
Anaplastic ependymomas have increased cellularity and show brisk mitotic activity. Microvascular proliferation and pseudopalisading necrosis are common. Perivascular pseudorosettes are universal, but true ependymal rosettes are rare or absent. GFAP expression is typically less uniform than in ependymoma.
Molecular genetics
LOH at 10q (PTEN) appear to be associated with anaplastic expression of ependymoma.
Prognosis
It remains unclear whether anaplastic histology proffers a worse outcome in patients with ependymal tumors, however, anaplstic ependymoma is more likely to occur in younger patients.
