Atypical and anaplastic meningiomas: radiology, surgery, radiotherapy, and outcome.

Out of 936 primary intracranial meningiomas, 94.3% were histologically benign (grade I), 4.7% atypical (grade II), and 1.0% anaplastic (grade III); one recurrence was sarcomatous (grade IV). Meningiomas with histologic anaplasia (grades II-IV) occurred in 12% of the men, but only 4% of the women. Only 26% of atypical or anaplastic meningiomas appeared completely innocent on a computed tomography scan. Angiograms, usually showing a meningeal feeding artery, suggested meningioma when computed tomography scans did not. At 5 years after complete removal, the recurrence rate was only 3% (21% at 25 years) for benign meningiomas, but 38% for atypical ones, and 78% for anaplastic ones. The median times to recurrence were 7.5, 2.4, and 3.5 years, respectively. In spite of postoperative radiotherapy, four of five anaplastic meningiomas recurred.