Approximately what percentage of adult brain tumors are metastatic?

• A. 10%
• B. 50%
• C. 75%
• D. 5%

Answer: (B)

In adults, metastases to the brain are the majority of brain tumors because cancer cells from other parts of the body often spread to the brain through the bloodstream. Roughly half of intracranial tumors in adults are metastatic, with primary brain tumors (like gliomas and meningiomas) making up the rest. So the best approximate percentage is about 50%. The other numbers would under- or overestimate how commonly metastases occur in adult brain tumors. Common sources for brain metastases include lung and breast cancers, among others.