MRI demonstrates typical findings of a large left sided acoustic schwannoma with cystic change - a common finding in larger schwannomas. 

The patient went on to have a resection. 

Histology

Microscopic Description:

Sections show a variably cellular tumor with compact areas of fascicular growth pattern and prominent nuclear palisading and less cellular regions composed of reticular cells in a microcystic pattern. There are sclerotic blood vessels, hemosiderin-laden macrophages and focal chronic inflammation.

Final Diagnosis:

Brain, left acoustic lesion: acoustic schwannoma.