subependymoma

Discrete lobulated ependymal nodules in the walls of the anterior third or posterior fourth ventricles commonly found at autopsy.

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sub·ep·en·dy·mo·ma (sub″ep-en″dĭ-moґmə) an ependymoma in which there is a diffuse proliferation of subependymal fibrillary astrocytes among the ependymal tumor cells. A few are malignant and others cause obstructive hydrocephalus, but many are clinically silent and are discovered only at autopsy.

Subependymoma in fourth ventricle; appearing as a hypointense lesion in an axial T1-weighted MRI scan.