To assess the value of contrast-enhanced ultrasound and real-time shear wave elastography (SWE) in the differential diagnosis of benign and malignant thyroid nodules without enhancement.

From January 2018 to June 2019, 100 thyroid nodules were examined by contrast-enhanced ultrasound in the General Hospital of the People's Liberation Army. The lesions showed no enhancement, and all lesions were examined by SWE. Pathological results were obtained by biopsy or surgery in all patients. According to the pathological results, the patients were divided into either a benign group or malignant group. The characteristics of contrast-enhanced ultrasound, maximum elastic modulus (Emax), and average elastic modulus (Emean) were compared between the two groups. The diagnostic efficacy of contrast-enhanced ultrasound and SWE for benign and malignant thyroid nodules was analyzed using the four-fold table and ROC curve.

The rates of no enhancement of the boundary and no enhancement of the whole nodule, as well as Emax and Emean values were significantly different between the two groups (P<0.05). Clear boundaries were mainly seen in the benign group, while unclear boundaries were mainly seen in the malignant group. The whole nodules without enhancement were all seen in the benign group. Emax and Emean values in the malignant group were higher than those in the benign group. The sensitivity, specificity, negative predictive value, and positive predictive value of unenhanced unclear boundaries for the differential diagnosis of benign and malignant thyroid nodules were 56%, 75%, 90%, and 30%, respectively; the corresponding values of whole nodules without enhancement were 20%, 100%, 19%, and 100%, respectively. The areas under the ROC curves of Emax and Emean were 0.696 and 0.705, respectively. When Emax>45.0 kPa was used as the cutoff value, the sensitivity and specificity for diagnosing malignant thyroid nodules were 62.5% and 64.3%, respectively. When Emean>47.7 kPa was used as the cutoff value, the sensitivity and specificity for diagnosing malignant thyroid nodules were 56.3% and 94.0%, respectively.

If there is no enhancement on contrast-enhanced ultrasound, whether the boundary is clear and whether there is enhancement in the whole nodule can be used to distinguish benign and malignant thyroid nodules. SWE has an appreciated value for the differential diagnosis of benign and malignant thyroid nodules without enhancement on contrast-enhanced ultrasound, which can help avoid unnecessary puncture biopsy and surgical treatment.