Breast cancer is the second most common origin of brain metastases, after lung cancer, and represents 14-20% of all cases. Abnormalities of chromosome 17 are important molecular genetic events in human breast cancer, and several oncogenes and tumor suppressor genes are located on this chromosome. In about half of all human cancers, the tumor suppressor gene TP53, located at 17p13, is either lost or mutated. Loss of p53 protein function influences not only cell cycle checkpoint controls and apoptosis, but also the regulation of other important stages of metastatic progression, such as cell migration and tissue invasion. The aim of our study was to identify numerical aberrations of chromosome 17 and TP53 in 5 subjects with brain metastasis from breast cancer using dual-color fluorescence in situ hybridization experiments. Deletion of TP53 was the most frequent alteration observed, suggesting that if this alteration is present in the primary tumors, breast tumors with loss of TP53 copies have a poorer prognosis and a higher chance for metastasis. If this is true, the analyses of chromosome 17 and TP53 in primary breast cancer could be important for predicting its metastatic potential.