Also, thyroid disease can be hereditary. If she ends up having thyroid disease, I suggest you get yours checked, too.
:) Tamra
An adenoma is good, a benign tumor, no cancer. Many, many people have adenomas on their thyroids. I have four.
http://en.wikipedia.org/wiki/Adenoma
The suggestion is to give her an FNA if the tumor grows. An FNA is a fine needle aspiration, a biopsy, where they inject a small needle into the tumor, usually taking three samples, to see if any of the tumor has turned to cancer. I had the FNA on my nodules. It was less painful than a trip to the dentist, and I didn't need anyone to drive me home.
Your sister should follow up on this regularly. If her doctor wants to do the FNA, then I suggest she do it.
Also, is she suffering from any pains, depression, fatigue? People with thyroid disease tend to get nodules.
If so, then she should get this thyroid bloodwork:
TSH
FT3
FT4
Anti-TPO
TGab
Be warned, my doc did not see the need for the bloodwork because my TSH was 'normal', but his definition of normal is changing in the medical community. After I switched doctors, I had the Anti-TPO test and found out I have Hashimoto's Thyroiditis. If she is feeling lousy, just demand the bloodwork, even if the doctor is hesitant.
Take care...
:) Tamra