Performance of Preoperative Sonographic Staging of Papillary Thyroid Carcinoma Based on the Sixth Edition of the AJCC/UICC TNM Classification System

Abstract

The purpose of this prospective study was to evaluate the overall performance of sonography for staging papillary thyroid carcinoma. Ninety-four consecutive patients with papillary thyroid carcinoma underwent preoperative sonography. Two experienced radiologists prospectively evaluated primary tumors (e.g., diameter, number, presence of extrathyroidal invasion) and cervical lymph nodes for metastasis. A 5-point scale grading capsular abutment was used to evaluate the possibility of extrathyroidal invasion. Lymph nodes were divided into central and lateral groups according to N staging requirements. The sonographic criteria for lymph node metastasis were an absent hilum, hyperechoic change, a round shape, calcification, cystic change, or an abnormal color Doppler pattern. Sonographic results were correlated with histopathologic findings. One hundred twenty-seven cancers in the 94 patients were proven after surgery. Sonography accurately identified 75.9% (22/29) of patients with multifocal cancer and 83.3% (15/18) of patients with bilateral cancers. Using a cutoff value of 50% or more of the tumor abutting the thyroid capsule (grade 2), the sensitivity, specificity, and accuracy of sonography in predicting extrathyroidal invasion were 85.3%, 70.0%, and 74.5%, respectively, and the overall accuracy of sonography for T staging was 67.0% (63/94). One hundred forty-seven cervical lymph node levels were dissected. All six sonographic findings were significantly more frequent in metastatic lymph nodes in the lateral group. However, in the central group, only two criteria-calcification and abnormal Doppler pattern-were found to significantly predict the presence of metastasis. The overall accuracy of sonography for N staging was 71.3% (67/94). Sonography is a feasible tool to use for the preoperative staging of papillary thyroid carcinoma.