Need expert advice on MRI of Brain

My recent MRI stated there is thick and prominent pachymeningeal enhancement and there may also be leptomeningeal enhancement however this is equivocal. There is the appearance of sagging of intracranial contents with a horizontal course of the optic chiasm /which could indicate intracranial hypotension.  These findings could all be due to a previous lumbar puncture or spinal surgery -neither applies to me.  however clinical correlation should be made. Leptomeningeal carcinomatosis cannot be excluded and short term follow up exam is recommended.  No focal brain parenchymal gadolinium enhancement or other lesion is identified. Tests which I have completed:  Checked spinal fluid for cancer cells - negative.  P.E.T. taken yesterday with results due on Monday.  MRI of the lumbar/spine scheduled for Aug. 1st.  I have lung cancer in remission.  Do I need to have a biopsy to determine if this is cancerous or not.  History:  Visual loss with history lung carcinoma.  Can a biopsy be dangerous to perform?  Do I need to see brain tumor specialist or is a neurosurgeon sufficient to handle this problem?  Could this problem stem from something else besides cancer?  I am afraid of a biopsy  doing more damage than before.