Clinical feature assessment

In this study, we analyzed the associations between thyroid lymph node metastasis and the following potential risk factors: age (<45, 45–59 and ≥60 years old), gender (male and female), maximal tumor size (<0.5 and ≥0.5 cm), gland lobes of tumor (unilateral and bilateral), primary lesion number (solitary lesion and multifocal lesions), tumor invasion (capsular invasion and external gland invasion), and tumor locations by US examination.