Context An increased breast cancer risk in postmenopausal women during Menopausal Hormone Therapy (MHT) has been shown in the Women’s Health Initiative (WHI) study using estrogen in combination with progestogen but not in the estrogen-only arm. In vitro studies and animal experiments have shown that the progesterone receptor membrane component 1 (PGRMC1) is important for tumor proliferation induced by progestogens. Objective To investigate the expression of PGRMC1 in tissues of patients with primary breast cancer and benign breast diseases. To analysis the correlation of PGRMC1 with clinicopathological features and the expression of ER, PR, Ki-67 and Her-2. Methods Samples from 90 patients with breast cancer, 60 with benign breast disease and 60 with normal breast tissues between the years 2015 and 2017 were obtained with the patients’ consent. Each sample was evaluated for the ERa, PR, Ki67, Her-2 and PGRMC1 expression by immunohistochemistry using serial sections from paraformaldehyde block. Results Positive expression of PGRMC1 was 68.33% (57/90) in breast cancer, 28.33% (17/60) in benign breast diseases and 6.67% (4/60) in normal breast tissues. PGRMC1 expression was significantly correlated to tumor size, lymphatic metastasis and the histological grade, but no association was obtained between menstruation and expression of PGRMC1 in breast cancer. PGRMC1 positively correlated with ER, Ki-67 in breast cancer tumors (rs = 0.416，p = 0.004; rs = 0.438，p = 0.000, respectively), and with ER and Ki-67 in benign tissues (rs = 0.314，p = 0.015; rs = 0.315，p = 0.014, respectively), while PGRMC1 negatively correlated with Her-2 in both groups ( p > 0.05). Conclusion PGRMC1 expression is strongly associated with the biological behavior of breast cancer, and may serve as a useful prognostic indicator of the malignancy.