Solitary fibrous tumor of the meninges. Case report and review of the literature.

The authors present the case of a left frontal solitary fibrous tumor of the meninges. The gross appearance of the tumor was very similar to that of a fibroblastic meningioma. Histological examination showed a mixture of spindle-shaped and round cells arranged in a collagen matrix. Immunohistochemical staining of the tumor demonstrated diffuse positive staining for CD34 and vimentin. The tumor displayed no positive staining for markers of muscle, epithelial, glial, or neurocrest differentiation or for estrogen and progesterone receptors. The MIB-1 labeling index (the percentage of positive staining tumor cell nuclei), a marker of cellular proliferation, was 1.1%. Ultrastructural studies support attributing a mesenchymal, rather than meningothelial, nature to the tumor. A differential diagnosis is discussed and a review of the literature on these rare tumors is presented.