Diagnostic approach for evaluation of lymph node metastasis from thyroid cancer using ultrasound and fine-needle aspiration biopsy

OBJECTIVE. The purpose of our study was to investigate ultrasound criteria to determine the most accurate criterion to differentiate metastatic from benign lymph nodes on ultrasound and to evaluate the frequency of metastasis according to the cytology results. MATERIALS AND METHODS. One hundred eighteen consecutive patients with thyroid malignancy underwent fine-needle biopsy of suspicious lymph nodes. We investigated the diagnostic performance of each ultrasound feature (loss of fatty hilum, presence of cystic change or calcification, hyperechogenicity, and round shape) and ultrasound criteria 1 and 2. We considered criterion 1 to be if one of the aforementioned malignant ultrasound findings was present and criterion 2 to be if one of the aforementioned malignant ultrasound findings, excluding the loss of fatty hilum, was present. Cytology results were divided into metastasis, macrophages without malignant cells, cell paucity, and negative for malignancy, and we evaluated the frequency of metastasis. RESULTS. There were 91 metastatic and 27 benign nodes. The area under the receiver operating characteristic curve value of criterion 2 was significantly higher than that of criterion 1. The frequency of metastasis was highest with a cytologic result of metastasis (95.8%), followed by macrophages without malignant cells (87.5%), cell paucity (71.4%), and negative for malignancy (34.4%). CONCLUSION. The most accurate ultrasound criterion to differentiate metastatic from benign lymph nodes was ultrasound criterion 2 (any suspicious ultrasound features except for loss of fatty hilum), and we should not neglect lymph nodes with suspicious ultrasound features, even if they do not contain malignant cells on cytology.