Additional Study Information: This study is for women with breast cancer who will be undergoing lumbar puncture to evaluate for the presence of leptomeningeal metastasis, a complication in which the cancer spreads to the membranes (meninges) surrounding the brain and spinal cord. This condition is typically diagnosed by examining the cerebrospinal fluid obtained from the lumbar puncture using standard cytopathologic analysis. However, this analysis is insensitive and leptomeningeal metastasis is currently being underdiagnosed. The purpose of this research study is to determine if a new technology, the OncoCEETM Cell Enrichment and Extraction technology, a novel immunocytochemical microfluidic device, will provide improved sensitivity in the diagnosis of leptomeningeal metastasis from breast cancer through identification of circulating tumor cells in the cerebrospinal fluid as compared to standard cytopathologic analysis.