Meningeal gliomatosis with "negative" CSF cytology: the value of GFAP staining.

We report a patient with meningeal gliomatosis who had signs of meningitis, hypoglycorrhachia, and an intracranial mass. Despite suspicion of a primary intracranial neoplasm, repeated CSF cytologies were not diagnostic and led to a brain biopsy for diagnosis. Immunoperoxidase staining for glial fibrillary acidic protein stained CSF cells that had been thought inflammatory on routine cytology. This case and other reports demonstrate that multiple cytologic examinations may be negative despite extensive gliomatous infiltration of the meninges. Immunoperoxidase staining is useful in cases of suspected meningeal spread of glioma when suspicious cells are seen on routine CSF cytology.