How does metastasis occur?

➢ In the absence of a known primary tumor, a histological examination is necessary (on the most accessible lesion: on the primary lesion if it is found, another metastatic site or on the brain biopsy). ➢ The study of stereotaxic brain biopsies or a metastasectomy allows in most cases to find or orient the clinician towards the primary tumor. ➢ This will be done based on architectural, cytological aspects, and especially the immunoprofile. ➢ It may happen (around 10% of cases) that the primitive is not found. They are generally so-called adenocarcinomas then from unknown primary