Omniview of three-dimensional ultrasound for prospective evaluation of extrathyroidal extension of differentiated thyroid cancer.

Background: Differentiated thyroid cancer (DTC) accounts for the majority of thyroid cancers. The preoperative diagnosis of extrathyroidal extension (ETE) in DTC patients is highly important. However, two-dimensional ultrasound (2D-US) has several limitations in diagnosing ETE. This study aimed to evaluate the efficiency of OmniView of three-dimensional ultrasound (3D-OmniView) in assessing the ETE of DTC patients compared with that of 2D-US.

Methods: Patients who underwent thyroid surgery for nodules adjacent to the thyroid capsule between February 2016 and January 2018 were prospectively enrolled in this study. Both 2D-US and 3D-OmniView were used to evaluate ETE of thyroid nodules. The definition for ETE in ultrasound images was capsule disruption, or capsule disruption and surrounding tissue invasion. Intraoperative and pathological findings of ETE were considered positive. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, and area under the ROC curve (AUC) were calculated.

Results: A total of 176 DTC nodules from 137 patients were included in this study. ETE was identified in 67.0% of the nodules. The sensitivity, accuracy, NPV and AUC of 3D-OmniView for predicting ETE were significantly greater than those of 2D-US. The sensitivity and specificity of 2D-US and 3D-OmniView were 51.7% and 79.7%, respectively (P < 0.001), and 81.0% and 82.8%, respectively (P = 0.809). Both 2D-US and 3D-OmniView showed better efficacy in evaluating ETE in nodules > 1 cm than in evaluating ETE in nodules ≤ 1 cm.

Conclusion: 3D-OmniView was more precise in predicting ETE of DTC nodules than 2D-US. 3D-OmniView is recommended for further evaluation of all thyroid nodules adjacent to the thyroid capsule. ETE was easier to detect by ultrasound for nodules > 1 cm than for nodules ≤ 1 cm.