Metastatic breast cancer is a disease of early breast cancer that usually occurs several years after the early breast cancer. Breast cancer is the most common cancer among Iranian women. According to the new statistics in Iran 6 160 breast cancers are diagnosed in the country each year and 1 063 cases lead to death. In this paper, epidemiology, diagnosis and treatment have been investigated. In this study, case-control clinical trials and open studies with adequate data were collected. Due to the higher risk of age group 40-49 years and the advent of advanced breast cancer in Iranian women, the early diagnosis and determination of the exact size of the tumor before surgery is important in choosing a therapy plan. The decision on the therapy of invasive breast cancer depends on several factors such as cancer stage, tumor size and type, pathological and cytological status of the tumor, the patient’s opinion, the presence or absence of estrogen and progesterone receptors in the cytoplasm of tumor cells and so on. Metastatic breast cancer is a disease of early breast cancer that usually occurs several years after the early breast cancer. According to the new statistics in Iran 6 160 breast cancers are diagnosed in the country each year and 1 063 cases lead to death. In this paper, epidemiology, diagnosis and treatment have been investigated. In this study, case-control clinical trials and open studies with adequate data were collected. Due to the higher risk of age group 40-49 years and the advent of advanced breast cancer in Iranian women, the early diagnosis and determination of the exact size of the tumor before surgery is important in choosing a therapy plan. The decision on the therapy of invasive breast cancer depends on several factors such as cancer stage, tumor size and type, pathological and cytological status of the tumor, the patient’s opinion, the presence or absence of estrogen and progesterone receptors in the cytoplasm of tumor cells and so on.