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Subependymoma is a slowly growing, benign neoplasm composed of glial tumor cell clusters embedded in an abundant fibrillary matrix. These lesions are typically attached to the wall of the cerebral ventricles. Subependymoma corresponds to WHO Grade I glioma.
Subependymomas are often asymptomatic tumors discovered on autopsy. Autopsy series have estimated that subependymomas account for 8.3% of all ependymal tumors.
These tumors arise most frequently in the 4th ventricle, followed by the lateral ventricles. Less common sites include the 3rd ventricle, septum pellucidum, and spinal cord.
Subependymomas may become clinically apparent by causing obstructive hydrocephalus.
On MRI, subependymomas appear as sharply demarcated, non-enhancing lesions. Intra-tumoral hemorrhage and calcification may be present.
These lesions present as firm nodules of variable size, bulging into the ventricular lumen.
Subependymomas are characterized by clusters of isomorphic nuclei embedded in a dense fibrillary matrix of glial cell processes with frequent occurrence of small cysts. Mitoses are very rare or absent.
The molecular genetics of subependymomas have yet to be characterized.
Subependymomas are slow-growing lesions. Surgical exicison is curative.