Hi Elaine,
Always a pleasure to hear from you.
Great questions.
It is interesting when you have diffuse thyroid disease like Hashimotos, DeQuervains or Graves. The thyroid echogenicity will be reduced in all of these conditions. So a nodule that would normally be isoechoic will now appear as an echogenic nodule (I have heard of this being referred to as a “white knight” nodule).
So personally I call the echogenicity of nodules relative to what would be “normal” thyroid echogenicity.
It means you have to use a bit of common sense, but I am happy to bring a normal thyroid from another patient up on the PACS and compare with that. The differentiation between hypoechoic and markedly hypoechoic is still easy as the strap muscles remain unchanged in echogenicity.
The lesion behind the thyroid may have been one of three things.
Option 1: The most likely thing is that it was a tubercle of Zuckerkandl.
This is a small island of thyroid tissue posterior to the right or left lobe, it has a capsule separating it from the thyroid, but an isthmus like connection to the thyroid. They are particularly obvious in the setting of diffuse thyroid disease as the thyroid becomes hypoechoic and hence the capsule of the tubercle stands out a little easier. You will indeed see polar flow into the tubercle from the thyroid. They are quite common and often mistaken as parathyroid adenomas or thyroid nodules. I am pretty sure I covered these and showed some examples in the miscellaneous neck pathology webinar I published earlier this year on the website.
Option 2: less likely a lymph node. I include this as level 6 lymph nodes are common in patients with Hashimotos thyroiditis.
Option 3: less likely as well, a true parathyroid adenoma. Start with biochemistry and if the serum calcium and parathyroid hormone are both normal this makes it very unlikely. A sestamibi scan will determine for sure.
Steve