Vimentin filament-desmosome cytoskeleton of diverse types of human meningiomas. A distinctive diagnostic feature.

Ten human meningiomas of different histologic subtypes (endotheliomatous, transitional, fibroblastic, and angioblastic) were examined for the expression of intermediate-sized filaments (IF) and desmosomal plaque proteins (desmoplakins I and II), using immunofluorescence and immunoelectron microscopy. All meningiomas gave a strong positive reaction for vimentin as well as for desmoplakins. IF of the cytokeratin type, desmin IF, and glial filaments were not detected in any of these tumors. The exclusive expression of vimentin in these tumors was confirmed by two-dimensional gel electrophoresis and immunoblot analysis of cytoskeletal proteins obtained after microdissection of well-defined tumor areas. Ultrastructural immunolocalization showed that, in the various tumors, vimentin IF were attached to the desmosomal plaques. With respect to the markers examined, all of the diverse types of meningiomas reacted like their putative non-neoplastic counterparts, i.e., arachnoidal cells. Our results indicate that the different histologic subtypes of meningiomas are derived from cells of the arachnoidal layer. The exclusive expression of vimentin-type IF in combination with desmoplakins is very unusual and so far seems unique to arachnoidal and meningioma cells. We consider this unusual combination, i.e., vimentin IF and desmoplakin plaques, to be a diagnostic feature for meningiomas, and we propose that the cytoskeletal property be used in differential diagnosis of intracranial tumors.