Objectives: The purpose of this study was to evaluate whether a nodule with a taller-than-wide shape (ie, an anteroposterior diameter that is longer than the transverse diameter on a transverse or longitudinal plane [anteroposterior-to-transverse ratio] >1) is a good predictor of papillary thyroid carcinoma (PTC) according to nodule size.
Methods: We retrospectively examined 207 thyroid nodules in our hospital from September 2011 to February 2013. Nodules were divided into groups by size: small (≤0.5 cm; group A), medium (0.5-1 cm; group B), and large (>1 cm; group C). Sonographic features were defined as an anteroposterior-to-transverse ratio greater than 1, microcalcifications, blurred margins, and hypoechogenicity.
Results: An anteroposterior-to-transverse ratio greater than 1 was the most accurate sonographic feature for predicting PTC in small nodules, with high sensitivity (81.4%) and specificity (96.8%), but it was not accurate in large nodules (>1 cm). Microcalcifications showed higher sensitivity (P< .05) in large nodules (60.0%) than in small ones (27.9%). Hypoechogenicity and blurred margins showed high sensitivity (95.3% and 97.7%, respectively) but low specificity (19.4% and 29.9%) for diagnosis of PTC in small thyroid nodules. An anteroposterior-to-transverse ratio greater than 1 in conjunction with another sonographic feature achieved the highest diagnostic accuracy in small nodules.
Conclusions: The predictive values of sonographic features depend on nodule size. An anteroposterior-to-transverse ratio greater than 1, especially in conjunction with another sonographic risk factor, showed superior performance for PTC diagnosis in small nodules.
Keywords: anteroposterior-to-transverse ratio; nodule size; papillary thyroid carcinoma; sonography.
© 2015 by the American Institute of Ultrasound in Medicine.