Clinicopathologic assessment and grading of embolized meningiomas: A correlative study of 64 patients

BACKGROUND. Preoperative embolization of meningiomas is commonly performed to minimize intraoperative bleeding, thereby facilitating surgery and reducing the necessity for transfusion. However, the resulting necrosis and compensatory proliferation reportedly have hampered subsequent histologic grading. METHODS. The clinicopathologic features of 64 meningiomas embolized between 1989 and 1997 were assessed. Tumors were graded according to recently published criteria. RESULTS. A good embolization result (> 75% reduction in angiographic blush) was achieved in 52%. Histologically, embolized meningiomas showed higher frequencies of necrosis (89%), nuclear atypia (72%), macronucleoli (58%), sheeting (31%), high mitotic index (30%), and brain invasion (14%) when compared with nonembolized counterparts. Median mitotic and MIB-1 indices were slightly elevated (1.5 of 10 high-power fields and 1.6%, respectively). A significant degree of necrosis (> 10%) was found in 43% and was only roughly correlated with extent of angiographic blush reduction or embolization particle size. Histologic grade was benign in 57.8%, atypical in 40.6%, and anaplastic in 1.6%. At last follow-up, there were 13 recurrences, 11 in the atypical/anaplastic (41%) versus 2 in the benign (5%) subsets (P = 0.001). CONCLUSIONS. The authors conclude that 1) their grading scheme accurately stratifies embolized meningiomas, 2) extent of necrosis is difficult to predict using standard clinical parameters, and 3) their high incidence of atypical meningioma more likely reflects patient selection biases rather than artifacts induced by the embolization procedure.