Brain-invasive solitary fibrous tumor of the meninges: report of a case.

Solitary fibrous tumor is a mesenchymal neoplasm that most commonly arises in the pleura, but also in multiple extrapleural sites including, rarely, the meninges. Immunohistochemical findings facilitate its differentiation from other spindle cell lesions such as fibrous meningioma. Although the great majority of extrapleural solitary fibrous tumors behave in a benign fashion, only rare examples of brain-invasive tumors have been documented. We present a case of a brain-invasive solitary fibrous tumor arising in the meninges of a 40-year-old woman. The tumor was marked by focally prominent hypercellularity, moderate nuclear pleomorphism, and increased mitotic activity. Focal infiltration into the underlying brain parenchyma was observed. The tumor was CD34 positive and EMA negative.