Value of Contrast-Enhanced Ultrasound in Differentiating Clinically Atypical Subacute Thyroiditis from Papillary Thyroid Carcinomas

Our objective was to provide the various sonographic characteristics of clinically atypical subacute thyroiditis (CAST) in distinguishing CAST from papillary thyroid carcinomas (PTCs) by using conventional ultrasound (US) and contrast-enhanced ultrasound (CEUS). Forty-six CAST patients and 50 PTC patients were enrolled in this study. We evaluated the size, shape, margin, echogenicity, calcification, vascularity and CEUS parameters for each nodule. The final diagnosis of CAST was confirmed via fine-needle aspiration (FNA) or surgery. Of the 46 CASTs, 13 (28.3%) were confirmed by surgery to be benign, and 33 (71.7%) were proven by FNA to be benign. Univariate analysis indicated that compared with PTCs, CAST lesions more frequently had wider-than-taller shapes, blurred margins, the absence of microcalcifications, peripheral high echogenicity, the absence of internal vascularity, hypo-enhancement, centrifugal perfusion and a peak intensity index <1 and area under the curve index <1 on pre-operative US and CEUS. A multivariate analysis revealed that clear margins, microcalcifications and centripetal perfusion were independent characteristics related to PTCs for their differentiation from CAST (all p values <0.05). Our study indicated that the pre-operative multiparameter US characteristics may serve as a useful tool for distinguishing CAST from malignant thyroid nodules to avoid surgical excisions or unnecessary FNAs.