The less invasive the procedure, the lower the risk of spread generally speaking. There is always a chance...I've had spread from someone bumping me too hard and from a lumbar sympathetic block meant to treat the RSD. Even a blood draw CAN cause spread...but all of those things are NOT the "norm" as far as spread. Most people never have any kind of spread. A flare up is another story. If it's not in your RSD area then you can still have a flare up for many reasons...number one just being the stress of the situation. If you need to have the biopsy done then I think you should do it but have your dr partner with you pain management doctor on how to reduce any discomfort and increased pain and minimize any risks of spread. You can't NOT live your life out of fear that things could get worse...just take the appropriate steps to minimize those risks.