Ultrasound-based follow-up of low-suspicion thyroid nodules with cytopathologic confirmation: is nodule growth associated with malignancy?

PURPOSE: This study aimed to evaluate the clinical utility of different ultrasound-based methods for assessing growth in low-suspicion thyroid nodules and to determine whether significant nodule growth (SNG) is associated with malignancy or thyroid neoplasm, as well as its implications for follow-up intervals.

METHODS

In this retrospective study, 309 patients with 334 low-suspicion thyroid nodules were analyzed. All nodules underwent at least three ultrasound examinations over ≥1 year and had cytopathologic confirmation. SNG was defined using three criteria: diameter-based criterion (DBC; ≥20% increase in at least two diameters with a minimum increase of ≥2 mm), volume-based criterion (VBC; ≥50% increase in volume), and change in the longest diameter alone (≥20% and ≥2 mm increase). Statistical associations between SNG and malignancy or thyroid neoplasm were evaluated using odds ratios (ORs).

RESULTS

Nodule growth was common, occurring in 57.8% of nodules according to DBC or VBC and in 51.5% based on the longest diameter, with substantial concordance between methods (κ=0.68). The median time to SNG was 2.9 years for DBC or VBC and 2.6 years for the longest diameter. SNG was not significantly associated with malignancy (OR, 1.19; 95% confidence interval [CI], 0.69 to 2.06) or thyroid neoplasm (OR, 1.05; 95% CI, 0.59 to 1.88).

CONCLUSION

Among cytopathologically confirmed low-suspicion thyroid nodules, SNG was not associated with malignancy or thyroid neoplasm. Measurement of the longest diameter alone provided a practical alternative to more complex growth assessment methods. Given that the median time to SNG exceeded 2.6 years, current ultrasound follow-up intervals for low-suspicion nodules may warrant cautious reconsideration.