Contribution of Computed Tomography to Ultrasound in Predicting Lateral Lymph Node Metastasis in Patients with Papillary Thyroid Carcinoma

Abstract

To evaluate the most accurate criteria using ultrasound (US) and contrast-enhanced computed tomography (CT) in predicting lateral lymph node metastasis in patients with papillary thyroid carcinoma (PTC). A total of 122 lateral cervical lymph nodes of 113 patients diagnosed with PTC underwent preoperative US-guided fine-needle aspiration biopsy (US-FNAB) and CT. Degree of enhancement (DOE) was calculated by the differences of Hounsfield units (HU) between the lymph node and the ipsilateral sternocleiomastoideus muscle. Standard reference was set by surgical pathology results. Diagnostic performances of US, CT, and cutoff value for DOE were analyzed. Seventy lymph nodes (57.4%) were metastases, and 52 (42.6%) were benign. The cutoff value of DOE on CT was 35.7 HU. Diagnostic performance of CT including DOE of 35.7 HU was lower than US, but without significance (P=0.321). When any suspicious CT feature was combined with the combination of suspicious US features, values of the area under the receiver operating characteristic curve decreased compared to the combinations of suspicious US features alone, 0.785 to 0.741, respectively (P=0.225). Contrast-enhanced CT does not greatly improve diagnostic values of US in the diagnosis of metastatic lateral cervical lymph nodes in patients with PTC.