What is brain cancer? Brain cancer is a serious form of cancer that occurs when there is an uncontrolled growth of cancer cells that form a malignant tumor in the brain. Normally, cells in the brain that are old or damaged will stop dividing and die. These cells are replaced by healthy young cells. Brain cancer occurs when old or damaged cells continue to divide and multiply uncontrollably. These abnormal cells eventually develop into a malignant mass of tissue (tumor) and crowd out and destroy healthy cells in the brain. As brain cancer grows, it interferes with vital processes and functions of the brain and spinal cord. Not all brain tumors are malignant (cancerous). Some types of brain tumors are benign (noncancerous). Either way, the effect of an expanding mass on nearby brain structures can lead to serious medical consequences. There are two main types of brain cancer: Primary brain cancer begins growing in the brain itself. Primary brain cancer is the rarest type of brain cancer. It can spread and invade healthy tissues in the brain and spinal cord but rarely spreads to other parts of the body. Each year about 19,000 people in the United States are diagnosed with primary brain cancer, according to the National Cancer Institute (Source: NCI). Secondary brain cancer is more common than primary brain cancer. Secondary brain cancer is caused by a cancer that has begun in another part of the body, such as in the lung, breast, kidney, skin or prostate that spreads to the brain. Secondary brain cancer is also called metastatic brain cancer. The prognosis for people with brain cancer varies depending on the cancer’s type, location, and stage of advancement; your age, general health status, and medical history; and other factors. Diagnosing brain cancer in its earliest stage provides the best hope for successful treatment or cure. Brain cancer can lead to life-threatening complications and be fatal, especially if it goes undetected and untreated. Seeking regular medical care offers the best chances of discovering cancer in its earliest, most curable stage. If you have brain cancer, following your treatment plan may help reduce your risk of serious complications of brain cancer.