Hi. Cancerous lesions in the thyroid are usually "cold" nodules (meaning, they don't take up and concentrate radioactive iodine as much). However, not all cold nodules are cancerous - only around 10-14%. If you have a solitary or suspicious nodule which is "cold" on thyroid scan, the next step would be to do either a fine needle aspiration biopsy or an ultrasound-guided biopsy to determine its histology (whether cancer or not).
I have recently had my thryoid removed and can tell you a little bit of information. After your ultra sound they are going to want to do a biopsy and then they will go from there. Because you have a history of cancer then they will more then likely want to do surgery depending on what they find. Don't worry to much, though. You will be back to normal in no time.