The markers of metastatic disease can thrive in the blood of breast cancer patients and cause it to spread to the brain. Researchers at Houston Methodist have identified a distinct group of cells in the bloodstream of patients who have breast cancer. Circulating tumor cells (CTCs) in breast cancer brain metastases (BCBM) are distinct from other circulating tumor cells. According to extensive clinical studies, approximately 20 percent of breast cancer patients will develop brain metastasis over their lifetime, and, in general, metastatic disease to the brain is estimated to become the number one cancer killer within the next decade. The researchers performed a comprehensive report of patient-derived circulating tumor cells at the gene expression level. By comparing the whole genome expression patterns of CTCs isolated from patient blood samples diagnosed with or without BCBM, they uncovered a 126 gene-signature that is specific to these brain metastatic CTCs. Future progress may result in a screening method to predict brain metastasis before the disease is detecable by current diagnostic standards.