Usually imaging can show whether it is solid or cystic, such is my understanding. A cyst usually has an outer wall and is filled with some sort of liquid/semi liquid. How it was explained to me when I was diagnosed with one at L4-5 years ago. I guess these are not unheard of. Ironically I worked as recovery (PACU) RN and occasionally would see patients listed for spinal surgery and removal synovial cyst and never gave it a second thought! My question to you is exactly how was the risk of biopsy worded? Asking as a nurse because any valid neurosurgeon and preoperative spinal surgery discussion will include possible risks of failure, including permanent paralysis, damage to cord, etc. They legally have to say that. I had to sign and initial documents acknowledging that before both my back and neck surgeries. (Even before some other surgeries!) NOT trying to diminish the seriousness of your situation - please understand! If Marshfield, UW and Mayo cannot provide any better answers, then I cannot think traveling elsewhere physically will make a difference. Obviously all your imaging can be seen remotely and your symptoms are well documented. What a frustrating and unfortunate circumstance. :<(