Breast cancer (BC) is the most frequent cause of leptomeningeal metastases (LM) .As for brain parenchymal metastases, the incidence of LM seems to be increasing, due to the growing incidence of metastatic BC, the improvement of survival and the poor diffusion of therapeutic agents into the central nervous system (CNS). Several prognostic factors have been identified, including the age at diagnosis, the functional and neurological status, the delay between the diagnosis of cancer and that of LM. The survival of patients is poor, less than 6 months in most published series. Several neuronal biomarkers could also be good candidates, such as the neurogranin CSF and/or serum levels or the CNS neurofilaments (NF), that seem to be a good reflect of axonal injury and neuronal loss. CNS NF have been investigated in several neurological diseases including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and multiple sclerosis, but not yet in CNS metastases. Indeed, the creation of a clinico-biological collection seems to be of high value in order to investigate future biomarkers of interest

Breast cancer (BC) is the most frequent cause of leptomeningeal metastases (LM). As for brain parenchymal metastases, the incidence of LM seems to be increasing, due to the growing incidence of metastatic BC, the improvement of survival and the poor diffusion of therapeutic agents into the central nervous system (CNS). Several prognostic factors have been identified, including the age at diagnosis, the functional and neurological status, the delay between the diagnosis of cancer and that of LM. Other CSF biomarkers have been evaluated for the diagnosis of leptomeningeal metastases. Finally, the CellSearch® technique allows for the characterisation of proteins expressed by CSF tumors cells (E.G., HER2) and will make possible a better understanding of the physiopathology of tumor dissemination to the CS.

Other neuronal biomarkers could be interesting for the diagnosis of LM in BC patients. Among them, the protein Tau (total-Tau or T-Tau) is involved in several neurological diseases. However, to date, no study has evaluated CSF or serum T-Tau in LM from solid tumors.

Several neuronal biomarkers could also be good candidates, such as the neurogranin CSF and/or serum levels or the CNS neurofilaments (NF), that seem to be a good reflect of axonal injury and neuronal loss.

Inclusion Criteria:

1. Male or female patient ≥ 18 years-old, no age limit;
2. Histologically confirmed diagnosis of BC;
3. Hormone receptors and HER2 statuses of the primary tumor available;
4. Suspected LM based on clinical symptoms or signs, or radiological abnormalities;
5. Indication of diagnosis lumbar puncture decided by the oncologist in charge of the patient;
6. Patients must be affiliated to a Social Security System;
7. Patient information and written informed consent form signed prior to any study specific procedures.

Exclusion Criteria:

1. History of other cancer(s) than the BC (except completely resected non-melanoma skin cancer or successfully treated in situ carcinoma).
2. Hormone receptors and/or HER2 statuses of the primary tumor not available;
3. Patients with a medical contra-indication to the realization of a lumbar puncture;
4. Patients with psychological, family, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule;
5. Patients who are pregnant or breast-feeding.
6. Legal incapacity or limited legal capacity.