[A case of filamentous fungal infection showing tumor-like expansion in the cisterns].

A 67-year-old woman was admitted for headache. The initial MRI showed a gadolinium-enhanced lesion in the prepontine area. Initial and repeated CSF examinations were negative for the fungal infection. Since the enhanced lesion expanded in the cisterns, and showed tumor-like appearance, brain biopsy was performed at 3 months from her first admission. Histological studies revealed filamentous fungal infection probably caused by the pseudallescheria boydii. Intrathecal miconazole injection through the Ommaya reservoir successfully ameliorated patient's symptoms and the MRI findings. Primary cisternal fungal infection showing tumor-like expansion typically fails to demonstrate its supportive findings by the CSF examination. Therefore, histopathological assessment after brain biopsy should be considered in cases that are not conclusive by means of conventional laboratory examinations.