Long-Term Ultrasound Surveillance of Solid and Predominantly Solid Thyroid Nodules Reveals Two Distinct Absorption...

Area of Science:

• Endocrinology
• Radiology
• Oncology

Background:

• Thyroid nodules are common, and their behavior during surveillance requires understanding.
• Solid and predominantly solid nodules are frequently monitored using ultrasound.
• The absorption phenomenon, typically seen in cystic nodules, is less characterized in solid nodules.

Purpose of the Study:

• To characterize volume reduction in benign solid and predominantly solid thyroid nodules during long-term ultrasound surveillance.
• To describe distinct absorption patterns over time in these nodules.
• To compare clinical and ultrasound features between different volume change patterns.

Main Methods:

• Retrospective study of 34 solid/predominantly solid thyroid nodules from 32 patients.
• Longitudinal ultrasound surveillance over a median of 28 months.
• Generalized additive mixed models (GAMMs) and unsupervised clustering to analyze volume change trajectories.

Main Results:

• All nodules showed significant volume decrease (median reduction: 85.6%).
• Two patterns identified: rapid-absorption and slow-absorption groups.
• Slow-absorption nodules were more often in the lower pole and lacked Doppler flow; some showed changes in echogenicity/stiffness over time.

Conclusions:

• Solid thyroid nodules can undergo significant volume reduction, similar to cystic nodules.
• This absorption phenomenon in solid nodules may be underrecognized.
• Understanding diverse volume change patterns improves interpretation of nodule evolution during follow-up.