CT FEATURES OF MALIGNANT MENINGIOMAS AND MENINGEAL HEMANGIOPERICYTOMAS

OBJECTIVE: To correlate the computed tomography (CT) features with the histologic findings of meningiomas. PATIENTS AND METHODS: The authors reviewed 184 intracranial meningiomas (161 primary and 23 recurrent l esions in 172 patients) and classified the lesions on the basis of six histologic characteristics as benign (82), atypical (64), anaplastic (26) or sarcomatous (12). Among the last two groups, the characteristi cs of 12 tumours were histologically compatible with hemangiopericytom a. The authors also reviewed the available CT scans for 86 meningiomas : 51 benign lesions, 23 anaplastic or sarcomatous (13 primary and 10 r ecurrent), and 12 hemangiopericytomas (8 primary and 4 recurrent). RES ULTS: Of the 12 radiologic characteristics studied, 8 were associated significantly more often with malignant than with benign meningiomas: presence of necrosis (in 54% of primary malignant meningiomas and 8% o f benign cases), cysts (15% and 2%), poorly defined margins (38% and 6 %), hinges (23% and 4%), ''mushrooming'' (8% and 0%) and substantial e dema (31% and 8%); large size (62% and 25%); and absence of calcificat ions (100% and 58%). Despite the fact that the risk of malignancy of m eningioma was higher for men, patients with benign and malignant menin giomas did not differ by age or sex. In contrast, more of the patients with hemangiopericytoma were men (5 [56%] of 9 patients), and these p atients were younger (average age 45 years, compared with 57 years for those with all other types of meningioma). From a radiologic point of view, the presence of necrosis (in 38% of hemangiopericytomas and 8% of benign meningiomas) and large size (in 75% and 25%) distinguished h emangiopericytoma from benign meningioma. conclusion: None of these CT findings is an absolute sign of malignancy, but the association of tw o or more of them should suggest the aggressive nature of a meningioma .