This is a very old thread (6 yrs, to be exact) and traceI99 has not been active on the forum since I've been around, which is 5 yrs.... I doubt you will get a response to your post, other than mine.
Look at this website -- I was just diagnosed today with a 5-7 mm nodule on my thyroid isthmus and reading this site helped me become better informed.
http://www.medicinenet.com/thyroid_nodules/article.htm
I'm not really sure when the isthmus is involed vs. either the right or left or both sides. However, it is not tiny and large enough they may very well recommend having it removed .. however, no advice here as I'm not familiar with a nodule on the isthmus bcz most on the board are on the lobes.
Pls. let us know what you find out and how you are doing.
When they removed my right lobe they also took out the isthmus. I had 2 nodules on my right lobe.
Cheryl