Objective: To determine the risk factors of brain metastases of patients with  breast cancer.
Methods: Follow-up surveys were carried out in the patients with breast cancer who were treated at our hospital from 1997 to 2007. Of the patients， 133 cases having brain metastasis were considered as the study group and the other 145 cases without brain metastasis served as the control group. The factors related to brain metastasis were comparatively analyzed.
Results: The likelihood of brain metastasis of patients with breast cancer was increased in the conditions of histological grade 3， tumor diameter more than 5 cm， estrogen receptor (ER) negative and human epidermal growth factor receptor 2 (HER-2) positive. Other factors， including tumor stage， histological classification， progesterone receptor (PR) status， presence or absence of axillary lymph node metastases and menopausat status， were not obviously related to brain metastasis.
Conclusions: Histological grade， tumor size and HER-2 status are independent risk factors for breast cancer brain metastasis， while ER may be an independent protective factor against breast cancer brain metastasis.