Abstract:Objective To summarize and analyze the available data on relationship between autoimmune thyroiditis and breast cancer. Methods The relevant studies were collected by searching databases of PubMed, Cochrane Library, Embase and Google Scholar up to May 15, 2017. The relevant data were extracted and the statistical analyses were conducted by Stata 12.0 software. Results Of 3,059 identified studies, 9 were eligible and were included in our analyses (including 1,325 participants). There was a significant evidence of an increased risk of breast cancer in the patients with autoimmune thyroiditis [for thyroid peroxidase antibody, O^R = 2.66, 95% CI (1.93, 3.68); for thyroglobulin antibody, O^R = 2.30, 95% CI (1.67, 3.18)]. Conclusions The present results indicated that the serum levels of thyroid peroxidase antibody and thyroglobulin antibody are significantly higher in patients with breast cancer than in healthy controls.