Ultrasonographic features associated with false-negative and false-positive results of extrathyroidal extensions in papillary thyroid microcarcinoma.

PURPOSE: To assess the ultrasonographic features affect accuracy of extrathyroid extension (ETE) evaluation on preoperative ultrasonography (US) in papillary thyroid microcarcinoma (PTMC).

METHODS

Of the total patients who underwent thyroid surgery, 516 patients with a tumor measuring less than 1 cm on preoperative US were enrolled in this study. One blinded head and neck radiologist reviewed the preoperative US images to evaluate the US features of PTMC, and the pathologic reports were reviewed. The diagnostic accuracy rates, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy, were calculated, and the factors associated with false-negative and false-positive results for ETE were analyzed.

RESULTS

The sensitivity, specificity, PPV, NPV, and accuracy for predicting ETE according to sonographic criteria were 32.8%, 87.5%, 51.0%, 76.6%, and 71.7%, respectively. Non-adjacent to the trachea and unilateral lesion on US were significant factors associated with false-negative results.

CONCLUSION

Size, shape, and location of PTMC on US are important factors that affect the US results in ETE evaluation.