The Landscape of Tumor Dissemination in Leptomeningeal Disease: Mapping CTC Plasticity and Regional Heterogeneity Across Blood and CSF Compartments

Background/Objectives: Leptomeningeal disease (LMD) is among the most severe complications of metastatic breast cancer, with median survival measured in weeks. Definitive diagnosis relies on neuroimaging and cerebrospinal fluid (CSF) cytology, which carries a false-negative rate of 40–50% at a single lumbar puncture. Improved tools for detecting and characterizing tumor cells across systemic and central nervous system (CNS) compartments are urgently needed.