Atypical (anaplastic) meningioma: relationship between histologic features and recurrence--a clinicopathologic study.

Two-hundred-and-eighty meningiomas of the surgical pathological files of the Taipei Veterans General Hospital from the period 1976-1986 were reviewed by the authors without prior knowledge of clinical circumstances or outcome. Thirty-four cases were regarded as atypical or anaplastic based on high cellularity, pleomorphism and the presence of mitotic figures with 6 cases showing only the above features and the remaining 28 displaying in addition one or more of the following "ominous" variables: papillary formation, necrosis and invasion of the underlying brain. With a median follow-up of three years after surgery the recurrence rate was 44% (15 cases) for this group of tumors whereas the remaining 246 histologically benign meningiomas had a 6% recurrence rate during the same period. This difference was statistically significant (p less than 0.0001). Once the atypical or anaplastic character of a meningioma was established, no difference in the recurrence rate was found related to the number of mitoses and whether the additional ominous variables were present, alone or in conjunction with others. Immunostaining for vimentin, S100, fibronectin and EMA showed variable results in the 34 atypical meningiomas but without significant difference between those that recurred within 3 years and the ones that did not.