Yusuf ÖZTÜRK, Muhammet KOCABAŞ, Buğra KAYA, Melia KARAKÖSE
Endocrinology Research and Practice - 2026;30(2):112-119
Objective: About 2% of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) scans show incidental focal thyroid uptake, with malignancy observed in 20%-40% of such cases. International guidelines recommend fine-needle aspiration biopsy (FNAB) for those thyroid nodules confirmed by ultrasonography. The study aimed to evaluate the performance of the American College of Radiology, European (Eu), and Korean thyroid imaging reporting and data system (TIRADS) in the evaluation of thyroid incidentalomas detected by 18F-FDG PET/CT, in order to increase cost-effectiveness by avoiding unnecessary FNAB procedures and to avoid overdiagnosis that may cause anxiety in patients. Methods: A retrospective evaluation was conducted of individuals who underwent 18F-FDG PET/CT imaging between 2019 and 2024. The study cohort consisted of patients whose 18F-FDG PET/CT scans showed focal thyroid uptake and who underwent FNAB after ultrasonographic evaluation. Results: A total of 236 nodules were included in the study, and 16.1% were malignant. Receiver operating characteristic analysis was performed for maximum standardized uptake value (SUVmax) and all TIRADS systems to assess their diagnostic performance. The optimal cut-off value for SUVmax was 5.67. Among the ultrasound risk stratification systems (US RSSs), Eu-TIRADS demonstrated the highest diagnostic performance at the clinically accepted threshold of score >=4, with a sensitivity of 94.7% and specificity of 78.3%. In contrast, SUVmax >5.67 showed lower sensitivity (68.4%) and specificity (69.7%) compared with the US RSSs. Conclusion: The current study revealed that, for thyroid incidentalomas detected on 18F-FDG PET/CT, evaluation with FNAB is the appropriate approach for those with Eu-TIRADS score >= 4, regardless of nodule size. In this context, more comprehensive studies are needed.
