Intracranial metastases: therapeutic options.

Metastatic spread of tumour cells detached from systemic tumours into the central nervous system occurs hematogenously since lymphatic drainage is absent in the brain. Little is known about the precise mechanisms of tumour cell attachment in the brain and local progression of micrometastasis into clinically symptomatic tumours or into lesions visible on modern imaging techniques, such as magnetic resonance imaging (MRI). Intensive research activities are focused on these pathophysiological mechanisms [1]. It is known that metastases are able to produce and secrete angiogenic substances enabling these tumours to become vascularized and to open the blood–brain barrier locally. Different tumour entities reveal a different tendency to metastasise intracerebrally independently of their incidence. Therefore, the relative incidence of intracerebral metastases does not correlate with the systemic incidence of tumours. Metastases of breast cancer, lung cancer and malignant melanoma are common. Some tumours, even when systemic metastases are a common phenomenon, are almost never found intracranially, as is the case in prostate cancer. Even inside the intracerebral compartment different locations of metastatic preferences exist. Metastases from kidney cancer for instance, arising from highly vascularized kidney parenchyma, are more often found in the well vascularized choroids plexus of the lateral ventricle than in other brain areas.