What is the initial workup for a patient suspected of having thyroid cancer?

Initial Workup for Suspected Thyroid Cancer

Fine needle aspiration (FNA) of the thyroid nodule and clinically suspicious lymph nodes is the cornerstone of initial workup for suspected thyroid cancer, followed by thyroid and neck ultrasound. 1

Step 1: Clinical Assessment

• Evaluate for high-risk clinical features that increase suspicion for malignancy:
  • Firm, fixed nodule
  • Rapidly growing nodule
  • Enlarged regional lymph nodes
  • Vocal cord paralysis
  • Symptoms of invasion into neck structures
  • Family history of thyroid cancer 1
  • History of head and neck irradiation 1
  • Associated syndromes (MEN 2A/2B, familial adenomatous polyposis, Cowden's syndrome) 1
  • Age <15 years or male gender (higher risk) 1

Step 2: Laboratory Testing

• Measure serum TSH levels (ideally before FNA) 1

  • Higher TSH levels are associated with increased risk of differentiated thyroid cancer 1
  • Helps differentiate between subclinical and overt thyroid dysfunction 2

• Consider serum calcitonin measurement 1

  • Particularly valuable for detecting medullary thyroid cancer (5-7% of all thyroid cancers)
  • Has higher sensitivity compared to FNA for medullary thyroid cancer 1
  • European guidelines strongly recommend calcitonin screening 1
  • American guidelines are more equivocal about routine calcitonin measurement 1

Step 3: Imaging

• Thyroid and central neck ultrasound 1, 2

  • Essential first-line imaging to confirm presence of nodules
  • Evaluate suspicious ultrasound features:
    • Hypoechogenicity
    • Microcalcifications
    • Absence of peripheral halo
    • Irregular borders
    • Central hypervascularity
    • Regional lymphadenopathy 1

• Lateral neck ultrasound (optional) 1

  • Helpful to assess for lymph node involvement

Step 4: Fine Needle Aspiration (FNA)

• Indications for FNA 1, 2:

  • Any thyroid nodule >1 cm
  • Nodules <1 cm with suspicious clinical or ultrasound features

• FNA should be ultrasound-guided for accurate sampling 2

  • Target the largest nodule and any nodules with suspicious features 2

• Cytologic examination results typically categorized as 1:

  1. Carcinoma (papillary, medullary, or anaplastic) or suspicious for malignancy
  2. Follicular or Hürthle cell neoplasm
  3. Follicular lesion of undetermined significance
  4. Thyroid lymphoma
  5. Benign (nodular goiter, colloid goiter, hyperplastic/adenomatoid nodule, Hashimoto's thyroiditis)
  6. Insufficient biopsy (nondiagnostic)

Special Considerations

• For follicular neoplasia with normal TSH, consider thyroid scan to identify "cold" nodules 1

  • Surgery should be considered for cold nodules 1

• Pathology slides should be reviewed at the treating institution by a pathologist with expertise in thyroid disorders 1

• For microcarcinomas (≤1 cm), observation without surgical resection can be considered in select cases 3

Common Pitfalls to Avoid

1. Relying solely on negative FNA results: False-negative results can occur; clinical suspicion should override reassuring FNA in the presence of worrisome clinical findings 1

2. Overlooking medullary thyroid cancer: Consider serum calcitonin measurement, as FNA may miss medullary carcinoma without additional immunohistochemical studies 1

3. Unnecessary workup of incidental thyroid nodules: Not all incidentally discovered nodules require extensive evaluation; consider using risk stratification systems like the American Thyroid Association classification or ACR TI-RADS to determine which nodules warrant FNA 4, 5

4. Failing to correlate ultrasound findings with cytology: Ultrasound features should be integrated with cytology findings for optimal diagnostic accuracy 5

By following this systematic approach to the workup of suspected thyroid cancer, clinicians can effectively identify patients who require further intervention while avoiding unnecessary procedures in those with benign disease.