Corticosteroid sensitivity in gliomatosis cerebri delays diagnosis.

Purpose: To describe a patient whose diagnosis of gliomatosis cerebri was delayed for one year due mostly to dexamethasone.

Patients And Methods: A 78-year-old woman was followed in clinic for a year with a brain lesion suspicious but not definitive for glioma, whose clinical course and neuroimaging varied with use of dexamethasone. A first biopsy and MR spectroscopy did not find evidence of malignancy.

Results: A second biopsy demonstrated the correct diagnosis when the patient was on a very low dexamethasone dose. Hypercellularity and a positive KI-67 immunostaining confirmed a grade II astrocytoma, although the rapid and aggressive course without dexamethasone suggested a higher grade tumor.

Conclusion: As in primary CNS lymphoma, the diagnosis of gliomatosis cerebri can be unnecessarily delayed with dexamethasone use. Every effort should be made to biopsy these lesions before or shortly after the addition of dexamethasone.