Recently, Patel et al (2011) described the detection of breast cancer cells in the CSF using the Cell Search System (Veridex). [6] Using this method, the CSF is enriched immuno-magnetically for the epithelial cell adhesion molecule (EpCAM). Next nuclear staining with 4 ',6-diamidino-2-phenylindole (DAPI) and immunofluorescent detection with cytokeratin and CD45 is performed in 5 patients with leptomeningeal metastases from breast cancer and approximately 104 circulating tumor cells (CTCs)in 7,5 ml CSF were found, using this method. There seemed to be an association between the number of CTCs and response to intrathecal administered chemotherapy in this small group of patients.