To standardize reporting, the International Classification or pulmonary conditions) has declined, while there was a simultaneous increase in mortality from external causes, including accidents and suicide (22). Survivors and their families often face psychosocial challenges, diffculties with and dissemination of incidence and mortality data, ICCC's social relationships and educational attainment, as well as financial hardships related to the costs of medical care (22). high mortality. This, in turn, may hinder efforts to identify priorities for research, determine allocation of resources, and improve outcomes for the children most at risk. Pediatric CNS tumors illustrate this limitation, as the overall 5-year survival rate for this group is 77 percent, yet certain subtypes have extremely poor prognoses. For instance, children diagnosed out of 100,000 people each year in the United States, placing all pediatric cancers within this category. The Joint Action on Rare Major challenges in pediatric cancer research, specifically Cancers, in cooperation with the European Cooperative Study rare tumor research, include the small number of patients Group for Pediatric Rare Tumors, classifies very rare cancers as studies; clinical heterogeneity—differences in patient characteristics, disease severity and outcomes, and treatments used; limited understanding of the biology even less frequently, making them especially difficult to study. of rare tumors; lack of preclinical models; lack of new therapies; less interest from pharmaceutical companies; Due to unique biological and histologic characteristics, and constrained funding and limited infrastructure (26). heterogeneity of outcomes. For example, the overall 5-year organization—-rather than by anatomic site, which is the convention for adult cancers (24). This approach reflects the survival rates are only 60.7 percent for adrenocortical carcinoma—a rare cancer of the adrenal glands—22.6 an aggressive softissue sarcoma—-and just 2.2 percent for multiple sites throughout the body, such as neuroblastoma, diffuse intrinsic pontine glioma (DIPG), an aggressive form rhabdomyosarcoma, and Ewing sarcoma (see Molecular and of brain cancer (5,27,28). In contrast, the overall 5-year Cellular Influences Driving Pediatric Cancers, p. 30) (25). adult tumors, specialized classification of pediatric cancers is