Objective: To compare the diagnostic accuracies of US and CT in the preoperative evaluation of primary tumors and cervical lymph nodes in papillary thyroid carcinoma (PTC) patients, and to identify if CT provides additional diagnostic role compared to US alone in these patients.
Materials and Methods: A total of consecutive 299 patients with pathologically proven PTC underwent US and CT for preoperative evaluation. We assessed diagnostic accuracies of US,CT and combined US and CT (US/CT) for the evaluation of primary tumors and lymph node metastasis. Subgroup analysis was performed comparing papillary thyroid microcarcinoma (PTMC, 10mm or less in maximum diameter of tumor) with PTC more than 1cm in maximum diameter of tumor.
Results: In the evaluation of primary tumors, US predicted extrathyroidal tumor extension and bilateral malignancy more accurately than CT (p<0.05) for all lesions as well as for two subgroups. For predicting central node metastasis, US/CT was superior to US alone (p=0.009) in PTC more than 1cm, but there was no statistical difference between US/CT and US in PTMC. For predicting lateral node metastasis, US/CT did not produce significant differences than US alone for all lesions as well as for two subgroups (p>0.05).
Conclusions: High-resolution US can be a useful imaging modality for the preoperative evaluation of extrathyroidal tumor extension and lateral lymph node metastasis compared with CT. Especially in PTMC, CT had no additional diagnostic value compared with US alone in the evaluation of central and lateral lymph node metastasis.