ObjectiveTo detect the expression of contactin-1 (CNTN1) gene in the breast cancer tissues and explore the relation between the expression and prognosis of patients with breast cancer. MethodsThe clinicopathologic data of 35 patients with breast cancer who met the inclusion criteria from January to June in 2015 in the Shaanxi Provincial Cancer Hospital were retrospectively collected. The Western blot and immunohistochemistry methods were used to detect the CNTN1 protein expressions in the 35 breast cancer tissues and their corresponding tissues adjacent to cancer and the reverse transcriptase-PCR method was used to detect the CNTN1 mRNA expression. The relation between the CNTN1 protein expression and 5-year overall survival (OS) was analyzed. ResultsThe positive rate and expression level of CNTN1 protein in the breast cancer tissues were higher than those in the tissues adjacent to cancer [65.7% (23/35) vs. 45.7% (16/35), χ2=8.235, P=0.003; 0.825±0.221 vs. 0.412±0.117, t=12.556, P<0.001], and the expression level of CNTN1 mRNA in the breast cancer tissue was also higher than that in the corresponding tissues adjacent to cancer (0.763±0.218 vs. 0.353±0.135, t=11.162, P<0.001). The positive rates of CNTN1 protein were higher in the patients with larger tumor diameter (>2 cm), lower differentiation, later TNM stage (stage Ⅲ+Ⅳ) and axillary lymph node metastasis (P<0.05). The median OS of 35 patients with breast cancer was 47.3 months, which was 36.2 months and 52.5 months in the patients with high CNTN1 expression and low CNTN1 expression (median expression of CNTN1 protein was 0.785 as critical value) respectively (χ2=4.052, P=0.049). ConclusionPreliminary results of this study suggest that overexpression of CNTN1 gene might play an important role in occurrence and progression of primary breast cancer and is related to prognosis of survival.