Summary

Comprehensive ATA guidelines for evaluation and management of adult thyroid nodules and differentiated thyroid cancer (DTC), updating the 2009 version. Major changes include a sonographic pattern-based FNA decision framework, expanded role of molecular testing for indeterminate cytology, more conservative surgical approach (lobectomy acceptable for many 1–4 cm low-risk cancers), more selective use of RAI ablation in low/intermediate-risk disease, lower-activity RAI regimens, and a dynamic response-to-therapy risk restratification system. New sections address active surveillance for papillary microcarcinoma, kinase inhibitor therapy for RAI-refractory progressive disease, and management of advanced/metastatic DTC.

Key Recommendations

Measure serum TSH in initial evaluation of any thyroid nodule; if TSH is subnormal, obtain 123I radionuclide scan (hyperfunctioning nodules rarely require FNA).
Perform thyroid/neck ultrasound with cervical lymph node survey in all patients with suspected nodules; base FNA decisions on sonographic pattern combined with size (high suspicion ≥1 cm, intermediate ≥1 cm, low ≥1.5 cm, very low ≥2 cm or observe, pure cyst no biopsy).
Report FNA cytology using the Bethesda System; repeat FNA under US guidance for nondiagnostic results, and consider molecular testing (7-gene panel or gene expression classifier) for AUS/FLUS or FN/SFN to refine malignancy risk.
For DTC >4 cm, gross extrathyroidal extension, clinical N1, or M1: perform total/near-total thyroidectomy; for tumors 1–4 cm without ETE and cN0, either lobectomy or total thyroidectomy is acceptable; for <1 cm intrathyroidal cN0, lobectomy alone is sufficient.
Perform therapeutic central neck dissection for clinically involved nodes; prophylactic central neck dissection may be considered for advanced T3/T4 or cN1b but is not required for small noninvasive cN0 PTC.
Use AJCC/TNM for mortality staging and the 2009 ATA Initial Risk Stratification (low/intermediate/high) for recurrence risk; restratify dynamically using response-to-therapy categories (excellent, biochemical incomplete, structural incomplete, indeterminate).
Do not routinely give RAI remnant ablation in ATA low-risk DTC (including unifocal/multifocal papillary microcarcinoma); consider adjuvant RAI for intermediate risk; routinely give RAI for ATA high-risk disease.
For low-risk DTC requiring ablation, use low activity ~30 mCi 131I; rhTSH preparation is an acceptable alternative to thyroid hormone withdrawal in low/intermediate-risk patients without distant metastases.
Target TSH <0.1 mU/L for structural incomplete response or high-risk disease, 0.1–0.5 mU/L for intermediate risk or biochemical incomplete response, and 0.5–2 mU/L for low-risk patients with excellent response.
Follow patients with periodic serum Tg (with anti-Tg antibodies) and neck US; for ATA low/intermediate-risk patients with excellent response, lengthen Tg testing intervals to 12–24 months and do not routinely repeat TSH-stimulated Tg.
FNA biopsy malignant cervical lymph nodes ≥8–10 mm (central) and ≥10 mm (lateral) when result would change management; perform compartmental therapeutic neck dissection rather than berry-picking for biopsy-proven recurrence.
For RAI-refractory, progressive, symptomatic or threatening metastatic DTC, consider kinase inhibitor therapy (sorafenib or lenvatinib); use bisphosphonates or denosumab for diffuse symptomatic bone metastases; stable asymptomatic metastases can be observed on TSH suppression.

Thresholds & Doses

FNA size cutoffs by sonographic pattern: high suspicion ≥1 cm, intermediate ≥1 cm, low ≥1.5 cm, very low ≥2 cm (or observe), pure cyst no FNA
Estimated malignancy risk by sonographic pattern: high >70–90%, intermediate 10–20%, low 5–10%, very low <3%, benign cystic <1%
Suspicious lymph node FNA threshold: ≥8–10 mm smallest diameter
Calcitonin level >50–100 pg/mL suggests MTC; FNA washout calcitonin useful when basal 20–100 pg/mL
18FDG-PET focal thyroid uptake: ~35% malignancy risk; FNA if nodule ≥1 cm
Iodine supplementation: 150 μg/day if dietary intake inadequate
RAI remnant ablation activity: ~30 mCi for low-risk; up to 150 mCi for adjuvant therapy; avoid empiric activities >150 mCi in patients >70 years
Thyroid hormone withdrawal: LT4 withheld 3–4 weeks (LT3 substitution for first 2 weeks acceptable); target TSH >30 mIU/L before RAI
Low-iodine diet: ~1–2 weeks before RAI ablation/treatment
Maximum tolerated radiation dose: 200 cGy to bone marrow, ≤80 mCi whole-body retention at 48 hours
TSH suppression targets: <0.1 mU/L (high-risk/structural incomplete), 0.1–0.5 mU/L (intermediate-risk/biochemical incomplete), 0.5–2 mU/L (low-risk excellent response)
Tg thresholds for response to therapy: excellent = suppressed Tg <0.2 ng/mL or stimulated Tg <1 ng/mL; biochemical incomplete = suppressed Tg ≥1 ng/mL or stimulated Tg ≥10 ng/mL
Postoperative stimulated Tg >5–10 ng/mL increases likelihood of RAI-avid metastatic disease; <1 ng/mL highly reassuring
Definition of nodule growth: ≥20% increase in two dimensions (minimum 2 mm) or >50% volume change
Empiric RAI activity for metastatic disease: 100–200 mCi (100–150 mCi if ≥70 years)
Pulmonary micrometastases: repeat RAI every 6–12 months while disease remains RAI-avid and responsive
Pregnancy: avoid for 6–12 months after RAI; cumulative RAI ≥400 mCi in men may impair fertility (consider sperm banking)
Risk of second primary malignancy significantly increases with cumulative 131I activity >500–600 mCi
Age cutoff for AJCC staging: 45 years (under reconsideration; NTCTCSG suggests 55 years)
Papillary microcarcinoma definition: ≤1 cm; disease-specific mortality <1%, recurrence 2–6%
FTC vascular invasion: >4 foci or extracapsular vascular invasion = ATA high risk
Lymph node metastases stratification: ≤5 micrometastases <0.2 cm = low risk; >5 nodes or any ≥3 cm = high risk

Citations

Recommendation 8 / Table 6 / Figure 2 — Sonographic patterns and FNA size cutoffs
Recommendation 9 / Table 8 — Bethesda System diagnostic categories and malignancy risk
Recommendations 13–17 — Molecular testing for indeterminate cytology
Recommendation 35 — Extent of thyroidectomy based on tumor size and features
Recommendations 36–37 — Central and lateral neck lymph node dissection
Recommendation 48 / Table 11 / Figure 4 — ATA Initial Risk Stratification System (modified)
Recommendation 51 / Table 14 — RAI remnant ablation/adjuvant therapy indications by risk
Recommendations 55–56 — 131I activity for remnant ablation and adjuvant therapy
Recommendations 59, 70 / Table 15 — TSH suppression targets
Table 13 / Sections B27–B30 — Response-to-therapy reclassification (excellent/biochemical incomplete/structural incomplete/indeterminate)
Recommendations 96–98 / Tables 16–17 — Kinase inhibitor therapy and toxicity monitoring for RAI-refractory DTC
AJCC 7th Edition TNM Table 10 — DTC staging