Abstract: Objective:To investigate the protein expression levels of breast cancer metastasis suppressor 1 (BRMS1) and Con-nexin 43(Cx 43) in thyroid cancer and their correlation with clinicopathologic parameters. Methods:Immunohistochemistry Streptavi-din-Peroxidase method was used to detect the BRMS 1 and Cx 43protein expression in 195 tissue samples, including 90cases with thy -roid carcinoma, 45cases with thyroid adenoma, 30cases with nodular goiter, and 30cases with normal thyroid glands. Results: The positive rates of BRMS 1 and Cx 43expression was56.7% (51/90) and 41.1% (37/90) in thyroid carcinoma, respectively, which are sig-nificantly lower than the rates in thyroid adenoma, nodular goiter, and normal thyroid gland tissues (P<0.001). Of the three pathological types of thyroid cancer, the positive expression rate of Cx 43was 61.9% in papillary carcinoma,27.8% in medullary carcinoma, 27.3% in follicular carcinoma, and 12.5% in undifferentiated carcinoma. Statistical differences in the BRMS 1 expression among papillary car -cinoma and the other pathological types were also noted. Unlike the patients without lymph node metastasis, the positive expression of BRMS 1 and Cx 43proteins were both significantly low among patients suffering from nodal metastasis. Subgroup analysis shows that the positive expression of BRMS 1 and Cx 43protein gradually decreased with TNM staging. In addition, a positive correlation was ob-served between the BRMS 1 and Cx 43protein expression (r=0.494, P=0.032). Conclusion:The decreased expression of BRMS 1 and Cx43 proteins is significantly correlated with the metastasis of thyroid cancer and malignant grade. The combined detection of the two proteins can be ideal biomarkers for judging the prognosis of thyroid carcinoma.