Factors Responsible for Non-Diagnostic Cytology on Ultrasound-Guided Fine-Needle Aspiration of Thyroid Nodules

Introduction Fine-needle aspiration (FNA) is a well-recognized procedure for the diagnosis of thyroid nodules, with the advantage of being safe and inexpensive. Fine-needle aspiration cytology (FNAC) is mainly performed for nodules showing suspicious sonographic features that may require thyroidectomy. Even when FNAC is performed under sonographic guidance, the cytological specimen obtained may be inadequate, leading to a non-diagnostic outcome. The aim of this study is to determine the sonographic and technical factors influencing the outcome of FNAC. Material and methods This cross-sectional study was conducted prospectively at the radiology department, Dr. Ziauddin Hospital, Karachi, from January 1, 2019, to December 31, 2020. This study was approved by the Ethical Review Committee (ERC) of Ziauddin University. All the patients undergoing ultrasound (US)-guided FNAC of thyroid nodules were included. Patients with a history of previous thyroid surgery, very large thyroid lesions (>5 cm), and those with adjacent soft tissue pathology obscuring the assessment of thyroid nodules were excluded from this study. Result Out of 176 nodules studied, 14 were non-diagnostic and 162 were diagnostic. A 22G needle was used in most of the patients, i.e. 102 (57.3%), which demonstrated no relationship with the non-diagnostic results. According to Bethesda, 136 (77.3%) patients were benign, 22 (12.5%) had lesions with atypia/follicular lesions of undetermined significance, 14 (8%) were non-diagnostic and four (2.3%) were suspicious for malignancy. A subset, including 76 nodules, was categorized according to Thyroid Imaging Reporting and Data System (TIRADS) as follows: 28 (36.8%) nodules were moderately suspicious, 24 (31.6%) were mildly suspicious, 20 (26.3%) were not suspicious, and four (5.3%) nodules were benign. It was also observed that none of the hypoechoic nodules yielded non-diagnostic cytology. Conclusion This study concludes that radiologists must be aware of the technical details, cytologic preparation, and procedure-related complications associated with US-guided FNA to optimize patient care and the diagnostic outcome.