Metastatic tumors are the most common brain tumor in adults, arising from cancers elsewhere in the body that have spread to the brain. Between 200,000 to 300,000 metastatic brain tumors are diagnosed each year, often stemming from lung or breast cancers. While larger metastatic tumors may be surgically removed, smaller ones can be treated with gamma knife radiation therapy which focuses 200 small beams onto the tumor.

2. 4 Common Brain Tumors
 1. Metastatic
 The most common brain tumor among adults, metastatic tumors are classified
as secondary brain tumors, which means they arise from cancer that formed
elsewhere in the body and then spread to the brain. Though exact incidence
rates are not known, the American Brain Tumor Association estimates
between 200,000 and 300,000 metastatic brain tumors are diagnosed each
year. “As we’re doing better in controlling cancer systemically, we’re
beginning to see more metastatic tumors,” said Dr. Lustig, who also noted
that metastatic tumors most often stem from lung or breast cancer. Larger
metastatic tumors will often be surgically resected—meaning removed—while
smaller tumors may be treated with a gamma knife, which is a form of
radiation therapy that focuses 200 small beams of radiation onto the
tumorous area