What is "subependymoma"

A subependymoma is a type of brain tumor; specifically, it is a rare form of ependymal tumor.

The prognosis for a subependymoma is better than for most ependymal tumors, and is considered a grade I/IV tumor in the World Health Organization (WHO) classification.

They are classically found within the fourth ventricle, typically have a well demarcated interface to normal tissue and do not usually extend into the brain parenchyma, like ependymomas often do.