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Thyroid Nodules

Terra Swanson


  • ~50% of adults will have a thyroid nodule on ultrasound
  • Benign: goiter, cyst, inflammatory, Hashimoto’s, follicular adenoma (microadenoma)
  • Malignant: follicular, papillary, medullary, anaplastic, metastatic, thyroid lymphoma
  • Risk factors for malignancy: age <30, head or neck radiation, family history of thyroid cancer


  • Initial work-up after a nodule is found (either clinically or incidentally on imaging)
    • TSH, Free T4, Thyroid U/S


  • If Low TSH: Likely a hyperfunctioning nodule (benign in 95% of cases)
    • Order Iodine-123 or technetium-99m thyroid scan
      • If hyperfunctioning → measure T3/free T4 if ↑, treat for hyperthyroidism
      • If non-functioning → proceed as if TSH were normal
  • Normal or elevated TSH:
    • FNA indicated based on U/S findings listed below (determined by TI-RADS system)
      • Nodules >1cm that have high- or intermediate-suspicion pattern
      • Nodules >1.5cm that have low-suspicion pattern
      • Nodules >2cm that have very-low-suspicion pattern
    • FNA cytology determines the plan of action:
      • Benign → periodic US monitoring at 12-24mo, then at increasing intervals
      • Indeterminate → repeat FNA in 3-12 months
      • Malignant → surgical referral
  • Nodules that do not meet FNA criteria, US findings determine the timing for follow-up imaging:
    • High suspicion: 6-12mo
    • Low to intermediate suspicion: 12-24mo
    • Nodules >1cm with very ↓ suspicion OR pure cyst: >24mo if at all
    • Nodules <1cm with very ↓ suspicion OR pure cyst: no further imaging necessary