Changes in Phenotype and Genotype of Breast Cancers During the Metastatic Process and Optimization of Therapeutic Targeting (ESOPE)

Inclusion Criteria: To be eligible to participate in the study, patients must fulfill all of the following criteria: Female patients. Age ≥ 18 years. ECOG performance status ≤ 2. Metastatic breast carcinoma, either at diagnosis or at first metastatic relapse. Available FFPE +/- frozen primary tumor samples. Evaluable metastatic disease. Metastatic disease outside any previous radiotherapy field (e.g. sub-clavicular or internal mammary lymph nodes). Metastatic disease accessible to either percutaneous or surgical sampling. Signed written informed consent (approved by an Independent Ethics Committee and obtained prior to any study-specific screening procedure). Social and psychological welfare in concordance with compliance to the study. Exclusion Criteria: To be eligible to participate in the study, patients must fulfill none of the following criteria: Bilateral or multifocal breast cancer. Isolated local or contralateral relapse. Solitary bone and/or brain metastatic disease unless : Metastatic sites eligible for a therapeutic surgery. Metastatic sites sampled for diagnosis purpose. Past or current history of malignant neoplasms, except for curatively treated basal and squamous cell carcinoma of the skin. Carcinoma in situ of the cervix. Any coagulopathy contraindicating tumor biopsy. Presence of a contraindication to general anesthesia, if required.