Atypical and Malignant Meningiomas: Increasing Incidence?

Introduction: Traditionally, the vast majority of meningiomas have been benign lesions with a low propensity for regrowth or spread following gross total removal. Over the past five years, our center has encountered a sharp increase in the percentage of meningiomas with pathological evidence of atypical or malignant features. This report addresses our growing experience with this entity. Methods: We retrospectively reviewed records of all patients evaluated for a meningioma at our center from 2002-2009. Patients followed with serial imaging studies or treated presumptively with radiosurgery without pathological diagnosis were excluded from review. Results: Over an eight year period, we encountered 382 patients with a presumptive diagnosis of meningioma and operated on 187. Of these, 18 (9.6%) had atypical or malignant features on pathological evaluation. In this group, five had previously undergone cranial irradiation (three for childhood leukemia); the remainder had no obvious predisposing factors. Six involved the skull base; the remainder were convexity or parasagittal. Despite aggressive resection, all lesions recurred and required additional surgery and adjuvant radiotherapy and/or chemotherapy. Conclusions: Based on our experience, it is possible that the incidence of atypical/malignant meningiomas is increasing. This may be due to a growing population of childhood cancer survivors, though most patients had no obvious predisposing factors. The referral nature of our practice may have contributed to our encountering more complex lesions; but other than local edema, these lesions did not demonstrate unusual features suggesting malignancy on preoperative imaging. In our experience, meningiomas no longer represents a uniformly benign disorder. This information may be important when counseling patients regarding prognosis, particularly before a pathological diagnosis has been made. Categories: Radiation Oncology, Neurosurgery, Oncology