OP46 – Malignancy rate of suspicious thyroid nodules less than 1cm on various TIRADS

      Ha, Su Min1; Kim, Jae Kyun1; Baek, Jung Hwan2 1 Department of Radiology and Thyroid Center, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, 06973, Korea 2 Department of Radiology and the Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, Korea   Background/Purpose: In patients with active surveillance of papillary thyroid microcarcinoma (PTMC), definitive therapy, usually preceded by definitive diagnostic procedure, is not recommended until there is evidence of disease progression, as stated in American Thyroid Association (ATA) guideline. Because deferring definitive diagnosis and therapy until disease progression has no impact on disease-specific survival. Objectives: We evaluated the malignancy rate of thyroid nodules, further stratified by size cut off value 1cm, with suspicious finding on ultrasound using various malignant stratification systems. Methods: The data was retrospectively collected from nine university hospitals between January 2003 and June 2003, previously enrolled in the Korean Society of Thyroid Radiology (KSThR) multicenter study for ultrasound (US) differentiation between benign and malignant thyroid nodules. 829 thyroid nodules in 711 patients (620 women, 91 men, mean age, 48.7 years; range 6-98 years, 351 malignant and 478 benign nodules) were included. We calculated the malignancy rate of thyroid nodules, further stratified by size, according to recommendations, and using four different types of malignant risk stratification systems. We assessed factors that differentiate benign from malignant nodules by ?²test. Results: In less than 1cm suspicious thyroid nodules on US, the malignancy rates ranged from 77.4% to 82.8%; the lowest was from the KSThR, whereas the highest was by the Web-based system. Therefore, less than 1cm suspicious thyroid nodules on US were actually 17.2%-22.6% benign. Discussion & Conclusion: Biopsy should be considered before active surveillance to exclude benign nodules having suspicious US features. Biopsy could prevent unnecessary active surveillance and patients’ anxiety.   References:
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