Comparison Study of the Adequacy and Pain Scale of Ultrasound-Guided Fine-Needle Aspiration of Solid Thyroid Nodules with a 21- or 23-Gauge Needle for Liquid-Based Cytology: a Single-Center Study.

No published study has compared the cytological adequacy between different caliber needles in liquid-based cytology (LBC) after fine-needle aspiration (FNA) of thyroid nodules. This study aimed to compare cytological adequacy, pain scale, and associated complications depending on the use of a 21- and 23-gauge needle in LBC. From January 2017 to April 2017, 88 solid thyroid nodules (STNs) in 88 patients underwent consecutive ultrasonography (US)-guided FNA (US-FNA) by a single radiologist. The selection of the needle size was randomized and changed biweekly. After FNA, the pain scale and other complications related to FNA were immediately evaluated for each patient. In all cases, adequacy and cellularity in cytology were retrospectively investigated by a single cytopathologist. Of the 88 STNs, 10 (11.4%) showed inadequate cytology: 6 for 21-gauge and 4 for 23-gauge needles. The rate of cytological adequacy was higher in the 23-gauge needle group than in the 21-gauge group, but this was not statistically significant (p = 0.318). The mean values of the pain scale in the 21- and 23-gauge needle groups were 1.8 ± 1.3 and 1.4 ± 1.1, respectively, but this difference was not statistically significant (p = 0.567). There were no significant complications associated with US-FNA, except for one case of mild intrathyroidal hemorrhage. In US-FNA of STNs using LBC, the use of a 23-gauge needle may be recommended rather than a 21-gauge needle.