Dena, first of all....((((HUGS)))) i know this is really scary.
The reason your doctor said thyroid cancer would be good news is because the cure rate is very, very high. If you have to have cancer, this is a good one to get. I guess what she meant was that if this is what it is, it is thankfully easy to deal with. usually they surgically remove the entire thyroid gland, then blast any remaining tissue with radioactive iodine. Then the patient just goes on thyroid supplement for the rest of their life.
Fortunately, thyroid supplements are effective, simple, and ridiculously inexpensive. So hang in there--everything should be OK.
I will be thinking of you, waiting for more info...and if you have any questions or need me for anything, I'm here. One thing I do well is decipher what they are telling you. Just pm and I can give you a number and/or email address.