On thyroid nuclear scan, a nodule can be either "cold" or "hot", and this based upon the nodule's ability to trap and collect radioactive substances (such as radioactive iodine or other radioactive technicium used in nuclear medicine). These isotopes, which are administered either orally or through intravenous injection, subsequently go into the thyroid gland where their concentration causes the areas corresponding to the nodules to show up as black "hot" spots on the scan image.
Hot nodules are rarely, if ever, cancerous, and most commonly represent benign adenomas. Moreover, such hot nodules may simply be overproducing thyroid hormone and may cause hyperthyroidism. The larger the "hot" nodule the more likely it will be associated with hyperthyroidism.
A “lump” (or nodule) in the thyroid gland between the ages of 20 to 50 years old is a common finding, and most nodules or “lumps” in the thyroid are NOT cancerous.
The following qualities may be helpful in determining whether the nodule is benign or malignant:
-How long the nodule has been tgere
-Whether it is tender (painful to touch) or not
-If it feels soft, rubbery, or firm to the touch
-The blood tests of thyroid function
-Thyroid scans and uptake
The only test that can conclusively differentiate a benign from a malignant nodule is the fine needle aspiration (FNA). Your treating physician will decide whether or not you need to undergo FNA.