Ultrasound-guided fine-needle aspiration of benign thyroid cysts or partially cystic thyroid nodules: a preliminary study for factors predicting successful collapse.

No published study has evaluated factors that predict successful collapse of the cystic component of benign cystic thyroid nodules after ultrasound (US)-guided fine-needle aspiration (US-FNA). This study aimed to assess the collapse rate of the cystic component of benign cystic thyroid nodules after US-FNA and to evaluate the factors related to successful collapse of cystic component. Over a 2-year period, US-FNAs of fluid from the cystic components of 97 thyroid nodules with measured volume of >1 mL were performed, and for 80 nodules at least 1 follow-up US exam was performed. Each thyroid nodule was classified according to the largest diameter, percentage of cystic component, volume and colors of aspirate, degree of aspiration, and the time to the last US follow-up. The rate of complete collapse of the cystic component was 18.8 % (15/80). The success rate increased as the degree of aspiration increased (p = 0.0328), and there was a statistically significant difference between bloody and non-bloody aspirates (p = 0.0019). The time to the last US follow-up had statistically significant correlation with complete collapse rate (p < 0.0001), but largest diameter of thyroid nodule, percentage of cystic component, and volume of aspirate showed no significant correlation. Only 32 nodules were reexamined by US after more than 3 months, of which 11 showed complete collapse (34.4 %). In this study, rates of successful collapse of the cystic component after US-FNA of benign cystic thyroid nodules were higher in cases of complete aspiration and in those with bloody aspirates.