An unexpected corridor to brain metastasis

The brain is a main site of breast cancer metastasis, which inflicts a grim prognosis on patients (1). Leptomeningeal metastases are a fatal form of brain metastasis, with a median survival of less than 6 months after diagnosis (2). This kind of metastasis results from the spread of cancer cells to the membranous layers filled with cerebrospinal fluid (CSF) that surround the brain and spinal cord. However, the mechanisms involved in cancer spread to the leptomeninges remain unclear. On page 1317 of this issue, Whiteley et al. (3) report the characterization of a previously unidentified route by which breast cancer cells (BCCs) metastasize to the leptomeninges in mice, migrating from vertebral metastasis along the external surface of blood vessels. The findings elucidate how BCCs hijack migratory pathways normally used by neuronal cells and could inform future therapies.