Children are referred to the Pediatric Oncology Branch (POB) for possible enrollment in clinical protocols for the treatment of cancer. While some children are not eligible for a specific protocol, they may present with disease manifestations that offer the potential for important new insights into the pathogenesis or clinical behavior of their underlying disease. In addition, children who have completed participation in a clinical protocol but do not currently have therapeutic protocol alternatives may continue to provide POB with important information. Diseases of interest to the POB include, but are not limited to lymphoma, brain tumors, Ewings sarcoma, leukemia, neuroectodermal tumors, osteosarcoma, and rhabdomyosarcoma. Hence, serial clinical evaluation of such patients, including the performance of clinical, laboratory, and diagnostic studies to help elucidate longitudinally the underlying disease mechanisms, and when clinically indicated standard care therapies, will assist POB meet its overall mission.