What is the best technique to perform Fine Needle Aspiration (FNA) for thyroid nodules to avoid non-diagnostic results?

Best Techniques for Thyroid Nodule FNA to Avoid Non-Diagnostic Results

Ultrasound-guided fine-needle aspiration biopsy (FNAB) is the preferred method for thyroid nodule sampling, with proper technique including adequate sampling and immediate specimen assessment by a cytopathologist to significantly reduce non-diagnostic results. 1

Optimal FNA Technique Components

Preparation and Guidance

• Ultrasound guidance is essential - US-guided FNAB is accurate, economical, safe, and effective 1
• Ideally, serum TSH results should be known before FNA, though this may be impractical during initial visits 1
• Ensure proper patient positioning with neck extended
• Thoroughly clean the skin with antiseptic solution

Needle Selection and Approach

• Use 23-27 gauge needles (smaller needles cause less trauma and bleeding)
• Both long-axis (parallel) and short-axis (perpendicular) approaches are acceptable, as neither has been proven significantly superior in reducing non-diagnostic results (11.5% vs 16.3% respectively) 2
• For cystic and cavernous nodules, a single FNAB may be sufficient, but solid nodules typically require two FNABs or combination with core needle biopsy (CNB) 1

Sampling Technique

• Multiple passes (at least 2-4) through different areas of the nodule
• Apply capillary action rather than excessive suction to minimize blood contamination
• For mixed nodules, target the solid components
• For cystic nodules, aspirate fluid completely and sample the wall/solid components

Specimen Handling

• Immediate on-site cytological evaluation (when available) to assess specimen adequacy
• Proper slide preparation: both air-dried and alcohol-fixed slides
• Consider liquid-based cytology methods for better preservation

Special Considerations for Different Nodule Types

Cystic/Mixed Nodules

• Complete aspiration of cystic fluid
• Target the solid components and nodule wall
• Consider ethanol ablation for purely cystic nodules

Solid Nodules

• Multiple sampling from different areas
• For nodules ≥2 cm with gradual increase in size, ensure thorough sampling 1
• Consider core needle biopsy (CNB) if initial FNAB is non-diagnostic 1

Calcified Nodules

• Pay special attention to nodules with calcifications as they have 5.03 times higher risk of malignancy 3
• Target areas adjacent to calcifications
• Consider stronger suction technique

Follow-up for Non-Diagnostic Results

• Repeat FNAB is recommended for initial non-diagnostic results
• Optimal timing for repeat FNAB is approximately 10.7 months after initial non-diagnostic results for nodules ≥10 mm without concerning features 4
• For nodules with suspicious features, earlier repeat FNAB (within 3 months) is warranted 3

Pitfalls to Avoid

• Inadequate sampling (most common cause of non-diagnostic results)
• Excessive blood contamination
• Improper slide preparation
• Sampling only one area of a heterogeneous nodule
• Failure to target solid components in mixed nodules
• Not recognizing when to use CNB as an alternative to FNAB for persistently non-diagnostic nodules 1

Interpretation Framework

All FNA specimens should be categorized according to the Bethesda System for Reporting Thyroid Cytopathology 1:

1. Non-diagnostic/Unsatisfactory
2. Benign
3. Atypia of undetermined significance/Follicular lesion of undetermined significance
4. Follicular neoplasm/Suspicious for follicular neoplasm
5. Suspicious for malignancy
6. Malignant

Remember that pathology and cytopathology slides should be reviewed at the treating institution by a pathologist with expertise in diagnosing thyroid disorders 1, as false-negative results can occur despite proper technique.