Edema and malignancy in meningiomas.

PURPOSE In recent years there have been many attempts to define a subset of aggressive malignant meningiomas based on histopathology and imaging technologies. The purpose of this study was to evaluate the level of peritumoral edema and its volume using the imaging technologies, computer tomography and magnetic resonance imaging, and correlate these results with the histological WHO classification. Reported causes of tumoral edema and its relationships to the histological characteristics were also reviewed. METHODS The cases of 55 patients with meningiomas who underwent surgery at the Hospital das Clinicas (Fac Med Univ Sao Paulo) between September 1993 and September 1997 were reviewed. The level of edema according to the classification of Ide et al. (1995) was compared to the histological WHO classification. RESULTS Classification of the degree of edema was: level 0 edema--28 cases ; level I edema--19 cases; level II edema--8 cases. Histological classification was: benign meningioma--43 cases; atypical meningiomas--11 cases; malignant meningioma--1 case. There was a significant (P=.0089) correlation between the degree of tumoral edema and the histological characteristics. CONCLUSIONS These results suggest that the degree of edema as revealed by computer tomography and magnetic resonance imaging can be an important clinical predictive factor for the histological grade of the meningioma.