Preoperative assessment of extrathyroidal extension of papillary thyroid carcinoma: comparison of 2- and 3-dimensional sonography.

OBJECTIVES

The purpose of this study was to evaluate the diagnostic performance and interobserver agreement of 2-dimensional (2D) and 3-dimensional (3D) sonography for evaluating extrathyroidal extension of papillary thyroid carcinoma.

METHODS

A total of 79 papillary thyroid carcinomas in 79 patients who underwent both 2D and 3D sonography for preoperative staging of papillary thyroid carcinoma were included. When the lesion was abutting on the thyroid capsule on 2D sonography, 3D sonography was performed. Three radiologists reviewed 3 data sets: 2D sonography, 3D sonography, and a combined set of both for tumor staging. The diagnostic performance, including sensitivity, specificity, positive predictive value, negative predictive value, and accuracy, for extrathyroidal extension was analyzed. Interobserver agreement of the 3 radiologists was assessed with κ values.

RESULTS

The overall accuracy rates for 2D sonography, 3D sonography, and the combined set in predicting extrathyroidal extension were 60.8%, 66.2%, and 67.9%, respectively. The accuracy of the combined set was significantly higher than that of 2D sonography (P = .016). The interobserver agreement of the 3 reviewers was fair (κ = 0.33) for 2D sonography and moderate for 3D sonography (κ = 0.46) and the combined set (κ = 0.49).

CONCLUSIONS

Adding 3D sonography to 2D sonography could improve the accuracy and interobserver agreement for predicting extrathyroidal extension of papillary thyroid carcinoma.