Breast cancer as a heterogeneous sophisticated disease includes several group with discrete clinical consequences. The disease is the most prevalent malignancy after non-melanoma skin cancers and it is also considered as the second leading cause of death after lung cancer. In fact, breast cancer is account for 23% of all cancer cases and 14% of deaths from cancer. The major cause of breast cancer deaths is actually metastasis of the tumor. As a result, it is prominent to identify the disease mechanism and diagnose molecular tools in order to predict metastasis. The specimens were collected from 30 metastatic and 30 primary tumor tissues of breast cancer patients. After that, RNA extraction was accomplished by means of GeneAll kit and then was stored in -80 degrees. Then, cDNA synthesis was carried out by miscript II RT kit from Qiagenecompany. Finally, sybergreen Real Time PCR of all samples was done for miRNA124, miRNA130a and miRNA 16 as a reference by means of Pre-designed primers of Qiagene Company. The results of molecular expression study showed that the amount of miRNA 124 in metastatic tissues has approximately increased double of primary tumor tissues. It is also revealed that the amount of miRNA has similarly increased by about 1.7 times. According to recent results, it can be possible to regard molecule as a major cause of metastasis process in breast cancer.