What is the initial evaluation and management plan for a small single thyroid nodule?

Initial Evaluation and Management of a Small Single Thyroid Nodule

For small thyroid nodules (<1 cm), ultrasound surveillance is recommended as the initial approach unless specific high-risk features or clinical risk factors are present. 1

Initial Diagnostic Evaluation

Step 1: Laboratory Assessment

• Thyroid function tests (TSH) to determine thyroid functional status 1
• Serum calcitonin measurement to rule out medullary thyroid cancer 1
  • Higher sensitivity than fine-needle aspiration for detecting medullary thyroid cancer
  • Omitting this test could miss medullary thyroid cancer

Step 2: Ultrasound Evaluation

• Essential for characterizing nodule features and determining risk of malignancy 1
• Suspicious sonographic features include:
  • Hypoechogenicity
  • Microcalcifications
  • Irregular or microlobulated margins
  • Taller-than-wide shape
  • Extrathyroidal extension

Step 3: Risk Stratification Based on Size and Features

• Apply ACR TI-RADS (American College of Radiology Thyroid Imaging Reporting and Data System) 1
• For nodules <1 cm:
  • Generally, observation is recommended 2, 1
  • Exception: Fine-needle aspiration (FNA) is indicated if any of these risk factors are present:
    • History of head and neck irradiation
    • Family history of thyroid cancer
    • Suspicious features on palpation
    • Presence of cervical adenopathy
    • Subcapsular location of nodule

Management Algorithm

For Nodules <1 cm WITHOUT Suspicious Features:

1. Surveillance with ultrasound 2, 1
   • Initial follow-up at 6-12 months
   • Then annually if stable
   • Consider repeat FNA if significant growth occurs or suspicious features develop

For Nodules <1 cm WITH Suspicious Features or Risk Factors:

1. Perform ultrasound-guided FNA 1
2. Based on FNA results:
   • Benign: Surveillance with ultrasound
   • Malignant: Surgical management (typically thyroidectomy)
   • Indeterminate/Suspicious: Consider molecular testing or surgical consultation 1

Special Considerations:

• If TSH is subnormal, perform radioisotope scanning before considering biopsy 1
• If nodule is part of a goiter with substernal extension, additional imaging with CT or MRI may be needed 1

Common Pitfalls to Avoid

1. Overtreatment of small nodules: Most thyroid nodules, especially those <1 cm, are benign and can be safely monitored 2, 3

2. Relying solely on size: While size is important, sonographic features are more predictive of malignancy risk 1, 3

3. Inadequate follow-up: Even benign nodules require periodic monitoring as they may grow or develop suspicious features 1

4. Ignoring clinical context: Clinical risk factors should always be considered alongside imaging findings 1

5. Insufficient expertise in cytopathology: Ensure cytology is reviewed by a pathologist with expertise in thyroid disorders 1

The management of small thyroid nodules requires balancing the low risk of malignancy against the potential harms of unnecessary procedures. A systematic approach using ultrasound characteristics and clinical risk factors allows for appropriate risk stratification and management decisions.