Human cell lines and xenografts. Schematic representation of how xenografts and cell cultures are established from human osteosarcoma. After excision, the tumor is dissected into pieces of which one ore more can be subcutaneously—or when technically possible orthotopically—xenotransplanted into nude mice. Please note that when dissemination is found in this situation, these cells should be originating from the primary tumor and more closely representing true metastasis.