Differences in the diagnostic performances of staging US for thyroid malignancy according to experience

The aim was to compare the diagnostic performances of physicians with different levels of experience for completing preoperative staging ultrasonography (US) for thyroid malignancy. From March 2009 to December 2009, 1421 patients underwent preoperative staging US by six physicians according to the sixth edition of TNM classification. Extrathyroidal extension was defined as a perimeter in contact with >25% of the thyroid capsule in a malignant lesion or loss of the capsule line. US features in diagnosis of lymph node metastases were round shape, hyperechogenicity, microcalcifications, cystic change, and peripheral vascularity. Diagnostic performances of the three experienced physicians (>7 y) and the three less experienced physicians (<2 y) were compared. The overall diagnostic performances of T, N1a, multifocality and bilaterality by the experienced and less experienced physicians were comparable. The positive predictive value of N1b by experienced physicians was 64%, whereas that by less experienced physicians was 38.5%. These results suggest that evaluation of lateral lymph node metastasis requires more experience than other aspects of staging US for thyroid malignancy.