Thyroid Nodules
Terra Swanson
Background
- ~50% of adults will have a thyroid nodule on ultrasound, 95% are benign.
- 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
Evaluation
- Initial work-up after a nodule is found (either clinically or incidentally on imaging), TSH, Free T4, Thyroid U/S.
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 (ATA guidelines or, more commonly, as 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
- Nodules that do not meet FNA criteria, US findings determine the timing for follow-up imaging (based on most recent ATA guidelines):
- 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.
- If FNA is obtained, cytology determines the plan of action:
- Benign → periodic US monitoring at 12-24mo, then at increasing intervals.
- Indeterminate → repeat FNA with additional sample collected for molecular testing if result is indeterminate again.
- Malignant → surgical referral.
