What is the management plan for a patient with bilateral solid thyroid nodules, some with worrisome appearances, and normal Thyroid-Stimulating Hormone (TSH) level?

Management of Bilateral Solid Thyroid Nodules with TR4 Classification

Fine-needle aspiration biopsy (FNAB) should be performed on the two left lobe nodules with worrisome appearance (TR4 classification) as the first step in management.

Initial Assessment and Risk Stratification

The ultrasound findings reveal multiple bilateral thyroid nodules with concerning features:

• Two solid hypoechoic nodules in the right lobe (0.69 × 0.30 cm and 0.59 × 0.51 cm)
• Three solid nodules in the left lobe:
  • Isoechoic nodule with hypoechoic halo and internal vascularity (0.86 × 0.78 cm)
  • Hypoechoic nodule with internal vascularity (0.52 × 0.44 cm)
  • Echogenic nodule (0.93 × 0.37 cm)

The report specifically identifies two nodules in the left lobe as having worrisome appearance (TR4), which indicates moderate suspicion for malignancy. The normal TSH level is noted, which is an important factor in evaluation.

Diagnostic Approach

1. Fine-Needle Aspiration Biopsy

• FNAB is indicated for the two TR4 nodules in the left lobe despite their size being <1 cm due to their suspicious ultrasound features 1
• Ultrasound-guided FNAB should be performed to increase accuracy, especially for these smaller nodules 1
• The biopsy should target any solid components with suspicious features (hypoechoic areas, areas with internal vascularity) 1

2. Laboratory Assessment

• TSH is already noted to be within normal limits, which is favorable
• Consider additional thyroid function tests (free T3, free T4) to complete the thyroid profile
• Calcitonin measurement may be considered if there is suspicion for medullary thyroid carcinoma, though this remains controversial in the United States 2

Management Algorithm Based on FNAB Results

If FNAB Results are Benign:

1. Regular ultrasound surveillance:
   • Initial follow-up at 1 month
   • Subsequent follow-ups at 3,6, and 12 months during the first year
   • Annual follow-up thereafter if stable 1
2. Monitor for:
   • Changes in nodule size
   • Development of new suspicious ultrasound features
   • Volume reduction rate (VRR) calculation for accurate assessment 2

If FNAB Results are Malignant or Suspicious:

1. Surgical management:
   • Total thyroidectomy for confirmed malignancy
   • Consider hemithyroidectomy for well-differentiated thyroid cancer confined to one lobe 1
2. Post-surgical follow-up:
   • TSH suppression therapy may be indicated depending on the type and stage of malignancy 2
   • Regular monitoring with ultrasound and appropriate tumor markers based on the type of malignancy

If FNAB Results are Indeterminate:

1. Consider molecular testing to further stratify risk
2. Repeat FNAB or proceed to diagnostic hemithyroidectomy based on clinical risk factors and patient preference

Special Considerations

Multiple Nodules Management

• Focus management on the most suspicious nodules (the two TR4 nodules in the left lobe)
• The presence of multiple nodules does not reduce the risk of malignancy in suspicious nodules 1

Pitfalls to Avoid

1. Do not delay FNAB of suspicious nodules despite their small size
2. Do not assume benign nature without cytologic evaluation
3. Do not start suppressive therapy with levothyroxine for benign nodules as it is not recommended 3
4. Do not perform unnecessary surgery without cytological confirmation of malignancy

Follow-up Recommendations

• Regardless of initial management, all nodules require systematic monitoring
• For benign nodules, follow-up should include ultrasound assessment at regular intervals
• If malignancy is confirmed and surgery performed, follow-up should include:
  • Thyroid function tests
  • Neck ultrasound
  • Appropriate tumor markers based on the type of malignancy
  • TSH suppression therapy if indicated 2

The management of thyroid nodules requires a systematic approach focusing on malignancy risk assessment. The presence of TR4 nodules necessitates FNAB regardless of size, with subsequent management guided by cytology results and clinical context.