parosteal osteosarcomajuxtacortical osteosarcomaosteosarcoma fibroblasticoextraskeletal osteosarcomametastatic osteosarcomachondroblastic osteosarcomaosteosarcoma metastasis sitesretinoblastoma osteosarcomaosteosarcoma chemotherapyconventional osteosarcomatelangiectatic osteosarcomaintramedullary osteosarcoma