Intracytoplasmic granulofilamentous inclusion bodies in a meningioma. Immunohistochemical and ultrastructural studies.

A case of cerebellar tentorial meningioma, with abundant, large, eosinophilic intracytoplasmic inclusions, was studied immunohistochemically and ultrastructurally. These intracellular inclusions were periodic acid-Schiff negative and ultrastructurally appeared as a condensation or aggregation of numerous intracytoplasmic intermediate filaments. These inclusions were not related to microvillus-lined ductules, indicating that these inclusions were distinct from pseudopsammoma bodies. In addition, these inclusions were intensely immunopositive for vimentin, whereas staining for glial fibrillary acidic protein, epithelial membrane antigen, cytokeratin, neurofilament, desmin, actin, or type IV collagen was negative. To our knowledge, this is the second reported case of meningioma with such unusual inclusions, but the first one to demonstrate that the intracytoplasmic intermediate filaments and their related inclusions were mainly composed of vimentin.