Extracerebral leptomeningeal astrocytoma mimicking a meningioma.

A 49-year-old woman with a two-year history of headaches that became progressively more frequent was found on computerized tomographic scan to have a dense, enhancing right frontoparietal mass. The tumor mimicked a meningioma in that it indented the inner table of the skull, was well demarcated from the underlying brain, and microscopically lacked the fibrillated cell processes and background that characterize astrocytomas. The 80- to 100-A cytofilaments were sparse and seen in few cells. It was only by the immunoperoxidase stain for glial acidic protein that the diagnosis of an extra-axial leptomeningeal astrocytoma was established.