Fine-Needle Aspirations in Atypia of Unknown Significance/Follicular Lesion Undetermined Significance (AUS/FLUS): Usefulness of Repeated FNA of Thyroid Nodules

Background: One of the first steps to determine the thyroid nodules nature is fine needle aspiration. Almost 15% of the nodules are reported as atypia of unknown significance/follicular lesion of unknown significance (AUS/FLUS), with no clear nature of benign or malignant cells. Objectives: This study aimed to evaluate the diagnostic value of repeated FNA in patients with AUS/FLUS undergoing thyroidectomy. Methods: This trial was conducted on 50 patients candidate for thyroid surgery due to both FNA report (AUS/FLUS) and clinical/ ultrasound findings from 2013 - 2014 in a referral surgery centre. First, a new FNA sample was taken from the lesion during surgery and was sent for cytopatholgy. Then, permanent pathology results (as gold standard method of diagnosis) and repeated FNA reports were analyzed and compared. The data were analyzed using SPSS Ver. 17, with P values less than 0.05 being considered significant. Results: The obtained results revealed that repeated FNA had sensitivity of 61.9%, specificity of 100%. It had 0% false positive and 38.1% false negative results. In our study the malignancy rate in repeated FNA was 26%. Also, according to the results, the positive and negative predictive values were 100% and 46.7% respectively, and the accuracy was reported as 71.4%. Conclusions: Repeated FNA for AUS/FLUS has low sensitivity and negative predictive value despite 100% specificity and positive predictive value. Also, the prevalence of “undetermined” reports in repeated FNA for such lesions is high. It is recommended that repeating FNA for AUS/FLUS may have a limited role in decision making for managing patients with this type of thyroid nodules.