Thyroid cysts treated with ethanol ablation can mimic malignancy during sonographic follow-up.

PURPOSE

We aimed to assess long-term ultrasound (US) findings after US-guided percutaneous ethanol ablation (EA) in benign thyroid cysts and predominantly cystic thyroid nodules.

METHODS

Forty patients with thyroid cysts (n = 14) and predominantly cystic thyroid nodules (n = 26) underwent long-term US follow-up (range, 12-36 months; mean, 18.2 months) after EA. US images of 40 post-EA nodules were retrospectively investigated to study the reduction in nodule volume and detailed US appearance.

RESULTS

On follow-up US, post-EA nodules showed the following features: Marked hypoechogenicity (n = 28), spiculated margin (n = 7), microcalcifications (n = 6), taller-than-wide shape (n = 2), centrally predominant vascularity (n = 3), no vascularity (n = 31), mixed vascularity (n = 3), and peripheral vascularity (n = 3). Post-EA nodules were diagnosed by US as benign (n = 3), probably benign (n = 2), borderline (n = 5), possibly malignant (n = 20), and malignant (n = 10). No statistical difference in the incidence of malignant US findings was observed between thyroid cysts and predominantly cystic thyroid nodules (p > 0.05, Fisher's exact test).

CONCLUSIONS

Long-term follow-up US after successful EA of benign thyroid cysts and predominantly cystic thyroid nodules revealed a high incidence of findings that are usually associated with malignancy. Recognizing these consequences of the procedure would help avoid unnecessary FNA on post-EA nodules.