health

Brain tumors are abnormal growths of tissue within the brain; about
150 different types have been identified. Brain tumors can be primary or
secondary. Primary tumors are tumors that start to grow within the brain.
Some are benign, meaning that they are not cancerous. Other primary
tumors are malignant, or cancerous. Primary brain tumors are less common
than secondary tumors, with most occurring in adults rather than children.
Secondary or metastatic tumors are cancers that start in other
organs—most often the breasts, colon, kidneys, lungs, or skin—and
then spread to the brain. Most brain tumors are metastatic cancers
rather than primary tumors; about a quarter of all adults being treated
for cancer in the United States eventually develop metastatic brain
tumors. It is rare, however, for primary tumors of the brain to spread
to other parts of the body.