This study will determine whether glioma cells can be detected in the bloodstream of patients undergoing surgery. If glioma cells are absent, it may mean they are unable to penetrate the blood-brain barrier. If they are present, they presumably can penetrate into blood vessels but they may be recognized and eliminated by the immune system, or they may escape detection yet not be able to take hold in the new microenvironment. The results of the study will add to the knowledge of the biology of these highly malignant tumors.