Pathologic significance of meningeal enhancement ("flare sign") of meningiomas on MRI

Abstract

Background: The purpose of this study was to clarify the pathologic features and clinical significance of the meningeal enhancement surrounding meningiomas ("flare sign") on contrast-enhanced T1-weighted magnetic resonance images (MRI).

Methods: The marginal dura mater of tumors was resected from nine cases of meningioma exhibiting a flare sign and used for histopathologic evaluation.

Results: Connective tissue proliferation was found in the dura mater in all cases, vascular proliferation was found in three, and tumor cell nests were observed in four cases. In one case, tumor cells were found 4.5 mm from the edge of the tumor. In another case, a meningothelial cell cluster was found.

Conclusions: These results suggest that tumor cell nests are present frequently in dura mater that exhibits the flare sign, and that the dura mater near these lesions should be resected as widely as possible.