Each year approximately 2,200 children in the United States are diagnosed with neuroblastoma, osteosarcoma, Ewing sarcoma family of tumors (ESFT), retinoblastoma, soft tissue sarcomas, adrenocortical tumors and liver malignancies. These aggressive pediatric solid tumors are developmental tumors that initiate during periods of tissue growth and morphogenesis in the neural crest, bone and soft tissues. The overall survival rate of these tumors in the advanced stage is less than 30%. Despite intensive efforts over the past three decades using multiple therapeutic modalities including chemotherapy, surgery, radiation, autologous bone marrow transplant and biological agents there has been modest improvement in the long-term survival of these advanced stage pediatric solid tumors. A better understanding of the molecular, cellular and genetic changes that occur in the developing tissues as tumors form could improve the treatment of these devastating cancers. In particular, chemotherapeutic agents may be more effectively targeted to key regulatory enzymes or proteins if the study had a better understanding of the pathways that are disrupted as cells progress from preneoplastic lesions to metastatic disease. The specific aim of this proposal is to identify the changes in gene expression that occur in neuroblastoma, retinoblastoma, osteosarcoma, Ewing sarcoma family of tumors \[ESFT\] and soft tissue sarcoma cells and to correlate these changes with genetic and cellular changes in the tumor cells. \[RNA\] ribonucleic acid and genomic \[DNA\] deoxyribonucleic acid will be isolated from neuroblastoma, retinoblastoma, osteosarcoma, ESFT \[Ewing sarcoma family of tumors\] and soft tissue sarcomas (both primary and metastatic lesions) following surgery or bone marrow aspiration of previously untreated patients. Additional testing will be conducted on tumor samples at any point during or following therapy in which a surgical specimen is obtained. When there is sufficient tumor sample remaining after pathological analysis and banking, fresh primary tumor cells will be used to prepare orthotopic xenografts and to establish models of each disease that recapitulate the advanced forms of neuroblastoma, osteosarcoma, Ewing sarcoma family of tumors \[ESFT\], retinoblastoma and soft tissue sarcomas. For a small group of these excess samples, this study will perform fixation for electron microscopy and process the samples for \[TEM\] transmission electron microscopy analysis. These studies will complement our active research program characterizing the molecular, cellular and genetic features of genetically engineered mouse models of each of these diseases. Biological samples from the cohort of patients treated at St. Jude Children's Research Hospital will be complemented with samples collected and processed by collaborating institutions around the world. Samples collected from international collaborators will be used for analysis of \[DNA\] deoxyribonucleic acid and \[RNA\] ribonucleic acid to complement the St. Jude Children's Research Hospital cohort. Through this collaboration the study anticipates that they will be able to obtain enough fresh tumor samples to improve their understanding of multistage tumorigenesis in pediatric solid malignancies.