childhood extraosseous osteosarcoma (MONDO_0004176, a Monarch Disease Ontology term) is an osteosarcoma arising from the soft tissue, and occurring during childhood. Also known as: childhood extraskeletal osteosarcoma, extraosseous osteosarcoma of childhood, paediatric extraosseous osteosarcoma, paediatric extraskeletal osteosarcoma, pediatric extraosseous osteosarcoma, pediatric extraskeletal osteosarcoma.