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Thyroid Nodules (cont.)

Thyroid Scanning

  • The use of radioisotope scanning has nearly been abandonded in the initial workup of a thyroid nodule. This test is performed by a nuclear medicine specialist. After a small, safe amount of radioisotope (123-iodine or Tc99) is taken by mouth or injected into a vein, the radiologist obtains pictures of the thyroid.
  • Nodules can be seen as dark spots (called "cold," because they do not take up the radioisotope) or bright spots (called "hot," because they do take up the radioisotope).
  • Nodules that concentrate the radioisotope are "hot" and usually make excessive thyroid hormone. "Hot" nodules are rarely associated with cancer and may not require FNAB investigation.
  • Nodules that do not concentrate iodine are "cold" and usually make less than normal amounts of thyroid hormone
    • More than 80% to 85% of all thyroid nodules are "cold," but only 10% of these represent a malignancy.
    • These nodules are typically more worrisome for cancer, and require evaluation with FNAB or surgery.
Medically Reviewed by a Doctor on 3/18/2015

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