Brain metastases are cancers that originally developed in other parts of the body but have spread to the brain. They are usually called secondary cancers, as they originated outside the brain, in areas such as the lungs, kidneys, or colon. The original source of cancer which caused the spread to other sites is often called the primary cancer.
Primary cancers that have high incidence of spreading to the brain include breast cancer and lung cancer. Others cancers that can cause brain metastases less frequently are those arising from the colon, testicles, ovary, and kidneys. Melanoma, which is a cancer caused by melanin-producing cells such as the skin, has also been implicated to cause cancer brain metastases in some cases.
The incidence of primary brain cancers are technically less common than the occurrence of brain cancer metastases. Generally, brain metastases are more often found in adults and the older people, and occur rarely in children. In the male population, lung cancer is usually the cause of brain metastasis, while in females, breast cancer is often the leading cause.
Cancers have many ways of spreading inside the body. They usually invade neighboring tissues and organs, leading to the growth of secondary cancers in these areas. When cancer cells reach the blood stream or the lymph nodes, they are often capable of spreading to neighboring areas as well as distant sites inside the body. For instance, cancer cells from the lungs usually spread to the brain via the arteries, as blood that passes through the lungs for oxygenation goes directly to the brain to provide oxygen to the brain tissues.
Brain metastases can grow in any part of the brain. They often cause direct damage to brain tissues, resulting in swelling that can often lead to compression of vital parts of the brain as the cancer grows. Symptoms of brain metastasis include headache, movement and speaking difficulty, double vision, and seizures.
Patients diagnosed with cancers usually undergo treatment to stop the growth of the primary cancer and to prevent the spread of cancer to other parts of the body. When brain metastases occur, the treatment technically failed to stop the cancer. The prognosis for someone with brain metastases is usually poor, and the outcome for the patient is often death. Treatment and management of patients with brain metastases often require the efforts of many medical experts, including neurosurgeons, neurologists, and oncologists.