Comparison of Ultrasonography and CT for Determining the Preoperative Benign or Malignant Nature of Thyroid Nodules: Diagnostic Performance According to Calcification

Background: The present study was designed to investigate the presence or absence of calcification and whether calcification size affect the diagnostic accuracy of ultrasonography (US) and computed tomography (CT) in predicting the benign or malignant nature of thyroid nodules. Material and Methods: From May 2014 to April 2019, 445 patients underwent thyroid US and neck CT before thyroid surgery. In each case, US and CT were retrospectively examined by radiologists. We divided the patients into 3 groups according to the type of calcification: no calcification, microcalcification, and macrocalcification. And macrocalcification group divided into rim calcifications and non-rim calcifications groups. We evaluated the diagnostic accuracy of US and CT for differentiating malignant from benign thyroid nodules using histopathological results as a reference standard. Results: In the overall population, adding CT to US resulted in greater sensitivity, lower specificity, and lower accuracy in the prediction of the benign or malignant nature of nodules. In the group with no calcification, US had a significantly greater accuracy than CT and combined US/CT. In the group with macrocalcification, especially in rim calcifications, adding CT to US resulted in greater sensitivity than US, and CT exhibited greater sensitivity and accuracy than US. Conclusion: US is superior to CT for the prediction of the benign or malignant nature of nodules in thyroid lesions according to calcification and CT is also currently not recommended as a routine imaging tool for thyroid nodules. However, the superior sensitivity and accuracy of CT in lesions with macrocalcification especially in rim calcifications may enable CT to play a complementary role in identifying benign and malignant nodules.