<qa>  What is the reason for the lack of identification of consistently expressed tumor-specific antigens withinDespite considerable advancements and promising clinical results observed in immunotherapy trials directed against adult malignant brain tumors, efforts in the immunologic treatment of pediatric brain tumors have been limited to relatively few notable studies. This is due, at least in part, to the often limited viable tumor tissue available for tumor cell-based vaccine preparations, and the lack of identification of consistently expressed tumor-specific antigens within these cancers. 