What is the approach to evaluating and managing a thyroid nodule?

Approach to Thyroid Nodule Evaluation and Management

The evaluation of a thyroid nodule should follow a systematic approach beginning with thyroid ultrasound and thyroid function tests, followed by fine-needle aspiration (FNA) based on nodule size and sonographic features to determine malignancy risk. 1

Initial Evaluation

Step 1: Thyroid Function Tests

• Measure serum TSH first
• If TSH is subnormal (suppressed), perform a radionuclide thyroid uptake scan 1
  • Hyperfunctioning ("hot") nodules rarely harbor malignancy and don't require FNA
  • For euthyroid patients, proceed with ultrasound evaluation

Step 2: Ultrasound Assessment

• Ultrasound is the best imaging modality to characterize nodules for malignancy risk 1, 2
• Suspicious sonographic features include:
  • Solid composition
  • Hypoechogenicity
  • Irregular margins
  • Microcalcifications
  • Taller-than-wide shape
  • Central hypervascularity 1, 2

Step 3: Risk Stratification Using TI-RADS

• ACR TI-RADS or similar risk stratification systems should be used to determine need for FNA 1
• FNA recommendations based on nodule size and risk category:
  • High suspicion: ≥1 cm
  • Intermediate suspicion: ≥1 cm
  • Low suspicion: ≥1.5 cm
  • Very low suspicion: ≥2 cm
  • Benign appearance: FNA not indicated 1, 3

Fine-Needle Aspiration

Indications for FNA

• Any nodule ≥1 cm with suspicious ultrasound features
• Nodules <1 cm with suspicious features AND:
  • History of head/neck irradiation
  • Family history of thyroid cancer
  • Suspicious cervical lymphadenopathy 1, 3

Cytology Interpretation

• Results should be reported using the Bethesda Classification System 1, 3
• Six categories with increasing risk of malignancy:
  1. Non-diagnostic/Unsatisfactory
  2. Benign
  3. Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance
  4. Follicular Neoplasm/Suspicious for Follicular Neoplasm
  5. Suspicious for Malignancy
  6. Malignant

Management of Indeterminate Cytology

• For indeterminate results (Bethesda III-V), consider:
  • Repeat FNA
  • Molecular testing (BRAF, RAS, RET/PTC, PAX8/PPARγ mutations) 1
  • Surgical consultation

Management Based on Evaluation Results

Benign Nodules

• Periodic ultrasound surveillance
• Consider treatment for symptomatic or cosmetic concerns:
  • Observation for small, asymptomatic nodules
  • Surgery for compressive symptoms
  • Thermal ablation for selected patients 1

Suspicious or Malignant Nodules

• Total or near-total thyroidectomy for:
  • Nodules ≥1 cm with malignant cytology
  • Nodules with extrathyroidal extension
  • Presence of lymph node metastases
  • Multifocal disease 4
• Less extensive surgery (lobectomy) may be acceptable for:
  • Unifocal tumors <1 cm
  • Intrathyroidal location
  • No extrathyroidal extension
  • No lymph node metastases 4

Special Considerations

Small Nodules (<1 cm)

• Generally don't require FNA unless high-risk features are present
• Non-subcapsular nodules <1 cm typically warrant surveillance rather than immediate FNA, even if classified as high-risk by TI-RADS 1

Multinodular Goiter

• Focus FNA on nodules with suspicious sonographic features
• Multiple nodules don't decrease the risk of malignancy in a suspicious nodule 1

Medullary Thyroid Cancer

• Consider measuring serum calcitonin as part of initial evaluation 1
• Particularly important with family history of MEN2 syndrome 1

Follow-up Recommendations

• Benign nodules: Ultrasound follow-up in 6-18 months
• Non-diagnostic FNA: Repeat FNA in 3-6 months
• Post-thyroidectomy: Regular monitoring based on risk stratification 4

The systematic approach outlined above helps identify the small subset of thyroid nodules that harbor clinically significant cancer (approximately 10%) while avoiding unnecessary procedures for benign nodules, which represent the majority of cases 2, 5.