Repeat ultrasound-guided fine-needle aspiration for thyroid nodules 10 mm or larger can be performed 10.7 months after initial nondiagnostic results

OBJECTIVE: The purpose of this study is to investigate when repeat ultrasound (US)-guided fine-needle aspiration (FNA) for thyroid nodules 10 mm or larger with initial nondiagnostic results due to inadequate or unsatisfactory specimen could be performed. MATERIALS AND METHODS: A total of 228 nodules 10 mm or larger with initial nondiagnostic results in 223 patients were classified into three groups according to the first follow-up US or US-guided FNA intervals after the initial US-guided FNA: within 3 months (group 1), 3-9 months (group 2), and more than 9 months (group 3). Nodules were classified according to size change. The malignancy detection rate and clinicopathologic characteristics were compared among the three groups. RESULTS: Seven nodules (3.1%) were malignant, and their cancer stages were the same as that determined at the initial US-guided FNA. Malignancy detection rates, as well as tumor size, extrathyroidal extension, and lymph node metastasis at pathologic analysis, were not significantly different among the three groups. Thirteen of 228 nodules (5.7%) showed increased size at a mean (± SD) of 34.5 ± 25.1 months (range, 10.7-84.7 months) after initial US-guided FNA, and one of the 13 nodules (7.7%) was malignant, a minimally invasive follicular carcinoma without lymph node metastasis found at 63.2 months. Of 177 nodules without change, six papillary thyroid carcinomas (3.4%) were found at a mean of 10.4 months. None of the 38 nodules with decreased size during a mean follow-up interval of 26.1 ± 19.8 months (range, 2.8-79.5 months) was malignant. CONCLUSION: Repeat US-guided FNA for initial nondiagnostic thyroid nodules after 10.7 months can reduce unnecessary repeat US-guided FNAs without progression of malignancy.