What is the recommended workup for a thyroid nodule?

Recommended Workup for Thyroid Nodules

The recommended workup for a thyroid nodule should begin with thyroid ultrasound as the essential first-line diagnostic procedure, followed by thyroid function tests and fine-needle aspiration cytology (FNAC) for nodules >1 cm or smaller nodules with suspicious features. 1

Initial Diagnostic Evaluation

Step 1: Thyroid Ultrasound

• Essential first-line diagnostic procedure to evaluate for suspicious sonographic features:
  • Hypoechogenicity
  • Microcalcifications
  • Absence of peripheral halo
  • Irregular borders
  • Solid composition
  • Intranodular blood flow
  • Shape (taller than wide) 1, 2

Step 2: Laboratory Tests

• Thyroid function tests (TSH, FT3, FT4)
  • Help differentiate between euthyroid and thyrotoxic nodules
  • Limited value in diagnosing thyroid cancer 1
• Serum calcitonin measurement
  • Should be an integral part of diagnostic evaluation
  • Higher sensitivity than FNAC for detecting medullary thyroid cancer (5-7% of all thyroid cancers) 3, 1

Step 3: Fine-Needle Aspiration Cytology (FNAC)

• Indicated for:
  • Any thyroid nodule >1 cm
  • Nodules <1 cm with suspicious clinical features (history of head/neck irradiation, family history of thyroid cancer, suspicious palpation, cervical adenopathy)
  • Nodules <1 cm with suspicious ultrasound features 3, 1
• Ultrasound-guided FNAC is preferred to improve diagnostic accuracy and reduce inadequate sampling rates 1
• Results should be reported according to the Bethesda Classification System 1

Management Based on Initial Evaluation

For Benign Nodules

• Observation/active surveillance for asymptomatic, benign nodules
• Regular ultrasound monitoring at 6-12 month intervals initially, then annually if stable
• Repeat FNAC if significant growth or development of suspicious sonographic features 1

For Suspicious or Malignant Nodules

• Surgical management with total or near-total thyroidectomy for:
  • Nodules ≥1 cm with diagnosis of differentiated thyroid carcinoma (DTC)
  • Metastatic, multifocal, or familial DTC regardless of size 3
• Less extensive procedures may be considered for small, intrathyroidal tumors with favorable histology 3
• Post-surgical radioiodine ablation for high-risk patients but not for low-risk patients 1

For Indeterminate Cytology

• Consider molecular testing to better discriminate benign from malignant nodules 1, 4
• If thyroid scan shows "hot" nodule with suppressed TSH, malignancy is unlikely 4, 5

Special Considerations

Nodule Shape and Malignancy Risk

• Spherical shape is associated with increased risk of malignancy
• Nodules with a long-to-short axis ratio greater than 2.5 are more likely to be benign 2

Common Pitfalls to Avoid

• Omitting calcitonin measurement, which could miss medullary thyroid cancer 3, 1
• Relying solely on reassuring FNA results when clinical findings are worrisome 1
• Failure to have cytology reviewed by a pathologist with expertise in thyroid disorders 1
• Performing unnecessary thyroid ultrasound for patients without palpable thyroid abnormalities 1, 6

Diagnostic Algorithm

1. Thyroid ultrasound for all nodules
2. Thyroid function tests and serum calcitonin
3. If TSH is suppressed, perform thyroid scan with 99Tc
4. For normal/elevated TSH or "cold" nodules on scan, proceed to FNAC if:
   • Nodule is ≥1 cm
   • Nodule <1 cm with suspicious features
5. Based on FNAC results:
   • Benign: Surveillance
   • Malignant: Surgery
   • Indeterminate: Consider molecular testing and/or surgery based on risk factors

This approach facilitates a personalized, risk-based protocol that promotes high-quality care while minimizing unnecessary testing 6.