[Interest of biological documentation on brain metastatic disease in breast cancer: A case report].

Breast cancer, after lung cancer, is the second major cause of brain metastases. In breast cancer, the prognosis is closely linked to the molecular subtype of the primary tumor. Targeted therapies, with or without cytotoxic treatment, have significantly modified overall survival in these patients. We report, the case of a patient suffering from breast cancer with brain metastasis in whom the biological documentation of the metastatic disease permitted to tailor the systemic treatment. Analysis of the surgical specimen revealed an immunohistochemical HER2 positive staining, which was not found in the primary tumor and therefore warranted trastuzumab administration. Another interesting insight based on this case report was to underline the phenotypic heterogeneity of the metastatic disease and its potential dynamic course as illustrated by the dissociated response to trastuzumab on body TEP-TDM in this particular patient. This case report also highlights the new place of the neurosurgeon in brain metastases management, not only as a participant in local treatment but also as a physician who is in fact involved in the delineation of the global oncological strategy in these patients as well as medical oncologists and radiation oncologists.