Abstract
Ultrasound (US)-guided fine needle aspiration (US-FNA) has played a crucial role in managing patients with thyroid nodules, owing to its safety and accuracy. However, even with US guidance, nondiagnostic sampling and infrequent complications still occur after FNA. Accordingly, the Task Force on US-FNA of the Korean Society of Thyroid Radiology has provided consensus recommendations for the US-FNA technique and related issues to improve diagnostic yield. These detailed procedures are based on a comprehensive analysis of the current literature and from the consensus of experts.
INTRODUCTION
Thyroid nodules are commonly encountered in clinical practice. Due to the excellent resolution provided by high-frequency ultrasound (US) devices, thyroid nodules as small as 2-3 mm can be detected and the prevalence of thyroid nodules has increased to 68%, according to a recent study (1, 2, 3). Considering that approximately 5-15% of detected nodules will eventually be verified as malignant through surgery (4, 5), all guidelines recommend US-guided fine-needle aspiration (US-FNA) to distinguish malignant from benign thyroid nodules, and the results substantially affect the management of thyroid nodules (1, 4, 5, 6, 7, 8, 9). Compared to palpation-guided FNA, the routine use of US guidance has significantly reduced the rates of nondiagnostic sampling and false-negative aspirates due to selective targeting of specific nodules, leading to an overall decline in the number of unnecessary surgeries performed for benign thyroid nodules and a concurrent increase in thyroid cancer yield in thyroidectomy specimens (4, 10, 11).
However, the success of US-FNA strongly depends on the experience of the operator and cytopathologist, as well as the intrinsic characteristics of the nodule. Therefore, about 0.4-40.7% of FNA results are insufficient for diagnosis and procedure-related complications still occur, albeit infrequently (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25). In addition, performing repeated FNAs potentially increases medical costs and the patient’s discomfort (26).
Accordingly, The Korean Society of Thyroid Radiology (KSThR) organized a task force comprised of radiologists with 10-20 years of experience in US-FNA of thyroid nodules to develop a consensus statement for the procedure. To retrieve relevant articles on the procedural aspects of US-FNA, a PubMed search was conducted through 2014 using the following search terms: thyroid nodule, thyroid malignancy, US, and fine-needle aspiration (FNA) biopsy. Based on the subsequent literature review and expert consensus of KSThR, this document will cover the technical aspects and pre-/post management of US-FNA of the thyroid nodule in detail, as well as the factors influencing cytologic adequacy.