Brain metastases are the spread of a primary tumor to the brain. Primary malignant brain tumors are tumors that start in the brain. They are actually quite rare, with an estimated 23,800 new cases in 2017. Brain metastases, commonly called “brain mets,” are far more common. The exact incidence of brain metastases is not known. Studies suggest brain metastases occurs in about 10%-30% of patients with cancer.
Among tumor types, lung cancers account for the highest number of brain metastases, with 25% of patients being affected at some time in their disease course. Other cancers that commonly metastasize to the brain include melanoma, breast cancer, colon cancer, and renal cell (kidney) cancer. Although these are the most likely types to do so, any type of cancer could spread to the brain.
Cancer can spread to any part of the brain. The most common site of brain metastases is the cerebrum, which is the largest and top part of the brain. Less often, cancer spreads to the cerebellum and brain stem.
The symptoms of brain metastases vary depending on which part of the brain is affected. Other health conditions can cause the same symptoms as brain metastases. See your doctor if you have these symptoms.
The most common symptom of brain metastasis is headache. Headaches may be caused by a tumour pressing on the brain, swelling (called edema), bleeding or hydrocephalus.
Other signs and symptoms of brain metastases include:

• nausea and vomiting
• seizure
• weakness or numbness in parts of the body, such as the face, arms or legs
• problems with memory and confusion
• changes in behaviour and personality
• problems with balance and coordination
• loss of bladder or bowel control (called incontinence)
• problems with speech
• problems with swallowing