subependymoma

Subependymoma is a rare, benign glial tumor of the central nervous system, categorized as a World Health Organization grade I tumor. It arises from subependymal glial cells lining the ventricular system and most commonly involves the fourth ventricle, though it can occur in the lateral or third ventricles. The tumor typically presents in adults and tends to be slow growing.

Many subependymomas are incidental findings. When symptoms occur, they are usually related to obstructive hydrocephalus or ventricular crowding and may include headaches, nausea, gait disturbance, or new focal neurologic signs depending on the tumor’s location.

On imaging, subependymomas are usually small, well-circumscribed intraventricular masses with minimal or no enhancement after contrast. They are often hyperintense on T2-weighted MRI and may contain calcifications or cystic changes. They can cause hydrocephalus by obstructing CSF flow.

Histologically, subependymoma shows low cellularity with small clusters or strands of uniform round to oval cells in a fibrous or mucoid stroma, sometimes with microcysts. Mitotic activity is absent or extremely rare, and necrosis is not typical. Perivascular pseudorosettes are uncommon, which helps differentiate it from ependymoma. Immunohistochemistry typically demonstrates GFAP positivity.

Management ranges from observation for asymptomatic, stable tumors to surgical resection for symptomatic or enlarging lesions. Gross total resection is often achievable and is associated with an excellent prognosis. Recurrence is rare, and malignant transformation is uncommon.