Help MD wants to do biopsy of lymphnodes after total thyroidectomy?tommorrow!

My doctors office called today and said that I have to come in to the medical center tommorrow and have an ultrasound with biopsy done to check for residual cancer and cancer in my lymph nodes. (I did have malignant lymph nodes removed during my first surgery) I am so surprised because this is the first time that I have heard about this he had never discussed it with me before.Has anyone else had anything like this done? I have to go through it tommorrow and I don't know what to expect or even what they are doing Please any help would be greatly appreciated
Heather in NH