The growth of abnormal cells in the tissues of the brain. Brain tumors can be benign (not cancer) or malignant (cancer).
Source: The National Cancer Institute's Dictionary of Cancer Terms (http://www.cancer.gov/dictionary)
oncology (on-KAH-loh-jee)
The study of cancer.
Source: The National Cancer Institute's Dictionary of Cancer Terms (http://www.cancer.gov/dictionary)
radiation (RAY-dee-AY-shun)
Energy released in the form of particle or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, medical x-rays, and energy given off by a radioisotope (unstable form of a chemical element that releases radiation as it breaks down and becomes more stable).
Source: The National Cancer Institute's Dictionary of Cancer Terms (http://www.cancer.gov/dictionary)
