This case resulted in considerable clinical and radiological discussion as to the potential differential diagnoses.

This ranged from demyelinating disease to metastases to an optic glioma.

The patient's visual loss temporarily responded to pulsed steroids.

Later the patient had a surgical biopsy performed at another institution which showed this to represent a B-cell lymphoma.

This is a very good grey-case or 'test the expert' case for educational meeting discussion.  This was made all the more difficult as the initial studies were for a para/sellar mass and hence received an MR protocol for pituitary imaging.  No DWI-ADC imaging was available which may have helped in the diagnostic process with lymphoma being a highly cellular tumor and hence showing diffusion restriction.

This is a rare site for a primary CNS lymphoma.