Thyroid Nodules

Background

• ~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
• RF for malignancy: Age <30 years; hx of head or neck radiation; family Hx of thyroid cancer

Evaluation

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

Management

• 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 >1 cm that have high- or intermediate-suspicion pattern
    • Nodules >1.5 cm that have low-suspicion pattern
    • Nodules >2 cm that have very-low-suspicion pattern
  • FNA cytology determines the plan of action:
    • Benign → periodic US monitoring at 12-24 months, then at increasing interval
    • 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: 6-12 months
  • Low to intermediate suspicion: 12-24 months
  • Nodules >1 cm with very ↓ suspicion OR pure cyst:  >24 months if at al
• ​​​​​​​Nodules <1 cm with very ↓ suspicion OR pure cyst: no further imaging necessary