Breast cancer is the most recurrent cancer in female population, its mortality is related to the presence of distant metastases. Distant metastasis begins as a small group of cells that spread regionally and remotely from the site of primary origin. Circulating tumor cells (CTC) are present in the blood of cancer patients and are therefore considered disease markers and precursors of metastasis. It is trascendental the review of the molecular aspects of the metastatic process, the available techniques for the enrichment, identification and molecular characterization of CTC, as well as some examples of its usefulness and clinical application in patients with breast cancer, including aspects related to perioperative management during breast cancer surgery.