What is the recommended management approach for a thyroid nodule classified as Bethesda II (Bethesda System for Reporting Thyroid Cytopathology)?

Management of Bethesda Category II Thyroid Nodules

For thyroid nodules classified as Bethesda II (benign), clinical follow-up with ultrasound is the recommended management approach, with no immediate surgical intervention required unless there are specific high-risk features present.

Understanding Bethesda II Classification

Bethesda II classification indicates benign cytology with a low risk of malignancy. According to studies:

• The malignancy risk in Bethesda II nodules is approximately 0-3% 1
• False-negative rates for Bethesda II nodules range from 7-15% 2, 3

Recommended Management Algorithm

Initial Management

1. Clinical follow-up with ultrasound surveillance

   • First follow-up ultrasound at 12-18 months
   • If stable, subsequent ultrasounds at 3-5 year intervals 4

2. No immediate surgical intervention unless:

   • Compressive symptoms are present
   • Cosmetic concerns exist
   • Patient preference after thorough discussion of risks/benefits

Surveillance Strategy

• For nodules <1 cm: Less intensive surveillance may be appropriate
• For nodules ≥1 cm: Regular ultrasound follow-up as outlined above
• Monitoring parameters: Size, echogenicity, margins, vascularity, and calcifications

When to Consider Repeat FNA

Repeat FNA should be considered if:

• Nodule growth of ≥3 mm in greatest dimension 5
• Development of suspicious sonographic features
• Development of compressive symptoms

Special Considerations

Small Nodules (<1 cm)

For small thyroid nodules (<1 cm) classified as Bethesda II:

• American Thyroid Association (ATA) guidelines do not recommend routine FNA for nodules ≤10 mm unless high-risk features are present 5
• Active surveillance is appropriate for these small nodules 5

Ultrasound Risk Stratification

Ultrasound features can help further stratify risk even in Bethesda II nodules:

• Low-risk US features: Purely cystic, spongiform, or predominantly cystic nodules with eccentric solid areas
• Intermediate-risk US features: Hypoechoic solid nodule with smooth margins, no microcalcifications
• High-risk US features: Irregular margins, microcalcifications, taller-than-wide shape 6, 7

Potential Pitfalls and Caveats

1. False-negative results: Despite Bethesda II classification, approximately 15% of nodules may be malignant on final pathology 2

   • Higher suspicion warranted for nodules with suspicious ultrasound features despite benign cytology

2. Nodule size considerations:

   • No positive linear correlation exists between nodule size and malignancy rate in Bethesda II nodules 2
   • However, larger nodules may warrant closer follow-up due to potential sampling error

3. Multiple nodules:

   • Each nodule should be evaluated individually based on its sonographic features
   • The most suspicious nodule should guide management decisions

Conclusion for Clinical Practice

The management of Bethesda II thyroid nodules should follow a risk-stratified approach. While most can be safely monitored with periodic ultrasound surveillance, attention should be paid to changes in size or characteristics. The false-negative rate, though low, necessitates ongoing vigilance, particularly for nodules with suspicious ultrasound features despite benign cytology.