Risk Stratification of Thyroid Nodules 10 mm in Diameter or Less: Strength and Pitfalls of the Ultrasonographic Assessment From a Cross-Sectional Study

Background: The selection of thyroid nodules ≤ 10 mm requiring characterization and treatment should be improved, as extensive detection, cytological assessment, and surgery of small and well-differentiated thyroid carcinoma are not cost-effective. Aim: To assess the accuracy of algorithms and ultrasonographic characteristics in selecting actual high-risk thyroid nodules ≤ 10 mm. Methods: A cross-sectional study was conducted on 38 of 112 outpatients who attended the University of Bari and underwent echo-assisted FNA for cytological characterization of thyroid nodules ≤ 10 mm (65 out of 118) and thyroid surgery from January 01 to December 31, 2016. Results: The median age of patients was 49.5 years [16; 69]. Thyroid cytology (SIAPeC-IAP 2014) was classified as TIR1 (one nodule), TIR2 (15), TIR3A (7), TIR3B (10), TIR4 (8), and TIR5 (24). Thirty-nine thyroid nodules were diagnosed as well-differentiated thyroid microcarcinoma. The clinical performance of 4 algorithms widely employed in clinical practice was low (AACE/ACE/AME, 38%; ACR-TIRADS, 45%; K-TIRADS, 60%; EU-TIRADS, 66%). Ultrasonographic features indicating high-risk nodules were hypoechogenicity (p = 0.0047), irregular margins (p = 0.004), and microcalcifications (p = 0.0019). Multivariable analyses indicated that hypoechogenicity was the main ultrasonographic characteristic associated with high-risk nodules (OR = 5.48, p = 0.0484). Discussion: Validated algorithms fail to select thyroid nodules ≤ 10 mm for which cytological characterization is needed. Our results are expected to improve the reliability of current algorithms by improving the weight of variables associated with a more consistent risk of thyroid malignancy in nodules ≤ 10 mm.