Atypical Meningioma: Distinguishing Features and Role of Adjuvant Radiation

Abstract

Meningiomas are the most common primary brain tumor in adults. Ninety percent of meningiomas are benign tumors, for which gross-total resection can achieve very low recurrence rates, with radiation therapy or radiosurgery reserved for recurrences or residual tumor that grows during serial imaging. At the other end of the spectrum, malignant meningiomas, although representing just 1% of meningiomas, have long been recognized to exhibit aggressive behavior that ultimately proves fatal regardless of extent of resection or whether adjuvant radiation and chemotherapy are utilized. Over the past two decades, there has been pathological recognition of a third type of meningioma known as “atypical,” with borderline histologic and clinical features between benign and malignant meningioma. Here, we review the histopathology, treatment, and long-term prognosis of atypical meningiomas. In particular, we review studies investigating the impact of radiation therapy and radiosurgery on the long-term recurrence rate of completely and incompletely resected atypical meningiomas.