Abstract: ObjectiveTo investigate the expression and clinical significance of C1orf63 in breast cancer. MethodsSixtyseven breast cancer tissues and adjacent noncancerous tissues were collected, and the expression of C1orf63 was detected by immunohistochemistry. The relationships between C1orf63 and clinical pathological characteristics were examined with χ2 test. Independent prognostic factors were performed by the Cox regression model. ResultsPositive cytoplasmic expression of C1orf63 was observed in 21 (31.3%) of 67 primary tumors, but not in their matched adjacent noncancerous tissues, with significant difference (χ2=24.90, P＜0.01). There were no relationships between C1orf63 and age (χ2=0.06, P=0.79), T stage (χ2=0.50, P=0.47), N stage (χ2=1.41, P=0.23), TNM stage (χ2=0.29, P=0.58), estrogen receptor (χ2=0.82, P=0.36), progesterone receptor (χ2=0.31, P=0.57), and human epidermal growth factor receptor 2 (Her2) expression (χ2=0.00, P=0.98). Multivariate analysis demonstrated N stage (HR=4.96, 95%CI: 2.0312.15, P＜0.01) and C1orf63 (HR=2.37, 95%CI: 1.055.37, P=0.04) were unfavorable prognostic factors. ConclusionThe high expression of C1orf63 in breast cancer may indicate poor prognosis.