Ultrasonographic Interval Changes in Solid Thyroid Nodules after Ultrasonography-Guided Fine-Needle Aspiration

Abstract

Objective: None of the previous studies have investigated the interval change in ultrasonography (US) features of solid thyroid nodules (STNs) after US-guided fine-needle aspiration (US-FNA). This study aimed to assess the prevalence and characteristics of US interval changes in STNs after US-FNA.

Materials and methods: This study included 257 STNs in 257 patients in whom thyroid US and initial US-FNA had been performed by two radiologists from January 2015 to June 2015. One of the radiologists performed single needle puncture in all cases, whereas the other radiologist used double or triple needle punctures. Follow-up US examinations were performed after 12.0 ± 6.0 months. We evaluated the prevalence and characteristics of post-FNA US interval changes through a retrospective analysis. In addition, multiple factors were correlated with post-FNA US interval changes.

Results: The number of needle punctures was one (n = 91), two (n = 163), and three (n = 3). Of the 257 STNs (mean diameter, 11.9 mm) in 257 patients, 35 (13.6%) showed an interval change in US features on follow-up US. Among them, 17 STNs (6.6%) showed newly developed malignant US features, including hypoechogenicity (n = 5), microcalcifications (n = 2), a spiculated margin (n = 4), hypoechogenicity with a spiculated margin (n = 5), and microcalcifications with non-parallel orientation (n = 1). Between patients who showed presence and absence of US interval changes, there were no significant differences in patient age, sex, nodule size, dichotomization, and location, Korean Thyroid Imaging Reporting and Data System categorization after FNA, practitioners involved, number of needle punctures, cytological findings, and interval between FNA and US follow-up (p > 0.05).

Conclusion: Awareness of US interval changes after US-FNA of STNs may be helpful for the management of STNs.

Keywords: FNA; Fine needle aspiration; Follow-up; Malignancy; Thyroid; Thyroid nodule; Ultrasound.

Fig. 1. Diagram illustrating enrollment of subjects and data analysis using study's algorithm.

STNs = solid thyroid nodules, US = ultrasonography, US-FNA = US-guided fine-needle aspiration

Fig. 2. 55-year-old woman showing interval changes in US features of STN after US-FNA performed using double needle puncture.

Before US-FNA, transverse (A) and longitudinal (B) gray-scale sonograms show STN with round shape in right thyroid lobe (arrows, 4.5 × 4.7 × 5.4 mm; K-TIRADS category 3). Radiologist with 5 years of experience performed US-FNA of this nodule, using double needle puncture. Cytological examination revealed that nodule belonged to Bethesda class II. At 12-month follow-up US after US-FNA, transverse (C) and longitudinal (D) gray-scale sonograms showed US interval changes in nodule (arrows). This nodule showed hypoechogenicity and spiculated margin, whereas nodule size decreased (3.7 × 3.8 × 4.6 mm; K-TIRADS category 5). Cytological examination after repeated US-FNA of this nodule revealed Bethesda class II. K-TIRADS = Korean Thyroid Imaging Reporting and Data System

Fig. 3. 56-year-old woman with interval changes in US features of STN after US-FNA performed using single needle puncture.

Before US-FNA, transverse (A) and longitudinal (B) gray-scale sonograms show STN with benign US features in left thyroid lobe (arrows, 6.0 × 10.4 × 11.2 mm; K-TIRADS category 3). Radiologist with 13 years of experience performed US-FNA of this nodule using single needle puncture. Cytological examination revealed that nodule belonged to Bethesda class II. At 12-month follow-up US after US-FNA, transverse (C) and longitudinal (D) gray-scale sonograms show US interval changes in nodule (arrows). This nodule showed decreased echogenicity and lobulated margin, whereas nodule size decreased (5.9 × 8.4 × 9.6 mm; K-TIRADS category 5). On same day, repeated US-FNA was performed for this nodule. Cytological examination revealed that nodule belonged to Bethesda class II.