Should You Repeat FNA on This TR3 Spongiform Nodule?
No, you should not repeat the FNA at this time. This nodule does not meet criteria for repeat biopsy based on current guidelines, and spongiform nodules have an extremely low malignancy risk even when larger than 2 cm.
Key Reasoning
Growth Assessment
Your nodule measurements show no significant growth by established criteria. The ACR TI-RADS defines significant enlargement as a 20% increase in at least two dimensions with a minimum 2 mm increase 1. Looking at your measurements:
- Previous: 3.4 × 2.2 × 3.7 cm
- Current: 2.7 × 1.9 × 4.3 cm
The dimensions actually show mixed changes (some decreased, one increased), which does not constitute the consistent bidirectional growth pattern required to trigger repeat FNA. This likely represents measurement variability rather than true growth.
Spongiform Morphology is Highly Reassuring
Spongiform nodules carry an exceptionally low malignancy risk. Research demonstrates that all spongiform nodules in a series of 96 cases had benign cytology, with suspicious ultrasound features being rare (only 2% had microcalcifications, 9.4% had taller-than-wide shape) 2. The AACE guidelines specifically recommend FNA for spongiform nodules only when ≥20 mm AND progressively increasing in size 3.
TR3 Classification Supports Conservative Management
For TR3 lesions, ACR TI-RADS recommends follow-up imaging at 1,3, and 5 years—not repeat FNA unless the nodule meets size thresholds for initial biopsy or demonstrates clear significant growth 1. The decision to repeat biopsy is typically driven by prior FNA results using the Bethesda System, not by stable or equivocal size changes 1.
Recommended Management Algorithm
Continue ultrasound surveillance:
- Next follow-up at the 3-year mark (if you're past 1 year from initial FNA)
- Compare measurements to the earliest baseline, not just the immediately preceding scan 1
- Look for consistent bidirectional growth of ≥20% in two dimensions plus ≥2 mm increase
Repeat FNA only if:
- True significant growth is documented (meeting the 20%/2mm criteria in two dimensions)
- New suspicious ultrasound features develop (microcalcifications, marked hypoechogenicity, irregular margins)
- The nodule reaches ≥20 mm AND shows progressive growth 3
Important Caveats
The natural history of benign nodules shows that only 15.4% grow over 5 years, and thyroid cancer was diagnosed in only 0.3% of followed nodules 4. Even when malignant, larger nodules (>2 cm) don't have progressively higher cancer risk beyond the 2 cm threshold 5.
Be aware that post-FNA ultrasound changes can occur in up to 13.6% of nodules, including newly developed features that may mimic malignancy 6. This makes it crucial to compare current images with pre-FNA baseline when available.
Your current nodule does not warrant repeat FNA. Continue surveillance ultrasound per TR3 guidelines and reassess only if true significant growth or new suspicious features develop.