First of all, know that we're sending good thoughts your way!!!!!
Next, listen to what everyone else has said. I know it'll be almost impossible but try to stay calm until you know anything further. I'm sorry that you got that letter, you really should have gotten a call from your doctor but that's in the past now. Again, the results could have been due to so many things. My Mom goes through that all the time, she now has to get an ultrasound with every mammogram since they always come back needing further results.
Think good thoughts and best of luck with your doctor this afternoon. We're hoping all turns out well!