To evaluate the combination of conventional ultrasound (US) and contrast-enhanced ultrasound (CEUS) in the differential diagnosis of papillary thyroid microcarcinoma (PTMC) and thyroid adenoma (TA).

From February 2013 to May 2017, 158 patients with single thyroid lesions (74 PTMC, 84 TA) in Drum Tower Hospital, Medical School of Nanjing University and Nanjing General Hospital were enrolled in this retrospective study. Before operation, all the patients were examined by conventional US and CEUS. The ultrasonic data and pathologic findings were available. The margin, microcalcification, the degree and homogeneity of enhancement of the TA and PTMC, and other variables were subjected to Fisher′s exact test or Mann-Whitney U analysis. The risk factors of thyroid microcarcinoma were screened by logistic regression analysis.

There were statistically significant differences in edge, aspect ratio, calcification and four consecutive US examination parameters in group TA and group PTMC (P<0.01). Qualitative analysis of CEUS intensification, intensity and uniformity, and quantitative analysis of Peak, Grad and Area showed that the differences were statistically significant (all P<0.01). The sensitivity, specificity and accuracy of US in diagnosing thyroid cancer were 82.1% (69/84), 66.2% (49/74) and 74.7% (118/158), respectively. Multivariate logistic regression analysis indicated that the risk factors of PTMC in ultrasonography were A/T ratio≥1, invasion and low enhancement (P<0.05). The receiver operating characteristic curve (ROC) of predictive value of Logistic regression model to determine the probability of thyroid malignant nodules was drawn, and the area under the curve was 0.887, and the sensitivity and specificity were 81.7% and 84.2% respectively.

Conventional US combined with CEUS is of great value in the differential diagnosis of thyroid tumors less than 1cm.