Abstract:Objective: To systematically evaluate the risk factors for lymphatic metastasis of thyroid microcarcinoma (TMC), and provide a basis for its treatment and assessment of metastatic risk. Methods: Studies published from January 2005 to July 2015 in domestic and international journals concerning the risk factors for lymphatic metastasis of TMC were collected by searching relevant databases, and then Meta-analysis was performed. Results: A total of 12 studies were included, involving 3 355 patients, of whom 1 292 cases (38.51%) had lymphatic metastasis. Results of Meta-analysis showed that young age (OR=1.46, 95% CI=1.20?1.78), male sex (OR=2.26, 95% CI=1.65?3.09), tumor size larger than 0.5 cm (OR=0.46, 95% CI=0.36?0.59), multiple primary lesions (OR=0.52, 95% CI=0.42?0.65), and presence of extracapsular invasion (OR=3.22, 95% CI=2.04?5.08) were risk factors for lymphatic metastasis of TMC (all P<0.05). Conclusion: TMC patients with age <45 years, male gender, tumor diameter ≥0.5 cm, multiple primary lesions, or presence of extracapsular invasion, should be vigilant of lymphatic metastasis.