Intermediate filaments in meningiomas.

The presence of intermediate filaments (IF) (diameter 10 nm) is a characteristic electron microscopic finding in the cytoplasm of meningioma cells. To identify these IF, immunohistochemical staining for cytokeratins and vimentin and two-dimensional (2-D) gel electrophoresis followed by immunoblot analysis were applied to a group of 16 meningiomas. Thirteen meningiomas were obtained directly from surgery and three came from an autopsy in which they were found in close proximity as discrete tumor masses. Except for the angioblastic type, all major histological variants were represented (nine transitional, four syncytial, and three fibroblastic). None of the meningiomas stained for epithelial or internal organ cytokeratins. With monoclonal antibodies, each of the meningiomas stained positively for vimentin. Two-D gels revealed vimentin and vimentin breakdown products as the only IF present; these findings were verified by immunoblots. The study concludes that vimentin is the IF present in fibroblastic, syncytial, and transitional meningiomas.