Metastatic cancer occurs when cancer spreads from its original location (primary tumour) to a new part of the body. Brain metastases occur when a cancer spreads to the brain from its primary site. Brain metastases are different from a cancer that starts in the brain (called primary brain cancer). Primary brain tumours occur much less often than brain metastases. Brain metastases are fairly common in people with cancer. It is estimated that 20–40% of intracranial tumours are metastatic.
Cancers that spread to the brain
Brain metastases only develop if a person already has cancer. Any cancer can spread to the brain. Some kinds of cancer are more likely than others to spread to the brain. The most common cancers that spread to the brain are:
- lung
- breast
- skin (melanoma)
- kidney
- testicular
- colorectal
- lymphoma (mainly non-Hodgkin lymphoma)
- leukemia
Occasionally, cancer spreads to the brain, but the original location of the cancer in the body (primary site) is not known. This is called cancer of unknown primary (CUP).
Where brain metastases occur
Cancers that start in the brain usually remain in one place. If there is more than one tumour in the brain, they are likely metastatic tumours.
Brain metastases can occur:
- on the surface of the brain
- The metastases occur in the membranes that cover and protect the brain and spinal cord (meninges and leptomeninges).
- Cancer that has spread to the meninges (called carcinomatous meningitis, leptomeningeal carcinoma or leptomeningeal metastases) is not common, but it is being seen more often.
- Certain types of cancer, such as lung cancer, breast cancer, leukemia and lymphoma, spread to the surface of the brain.
- within the brain
- The metastases occur in the cerebrum, cerebellum or brain stem.
- About 80% of brain metastases occur in the cerebrum (the largest part of the brain), 15% in the cerebellum and 5% in the brain stem.
Find out more about signs and symptoms, diagnosis, treatment, supportive therapies, follow-up after treatment and supportive care for brain metastases.