low grade central osteosarcoma (Monarch Disease Ontology identifier MONDO_0006271) is a low grade osteosarcoma arising from the medullary portion of the bone. It affects the long bones and is characterized by the presence of fibroblastic stroma and osteoid production. Pain and swelling are the usual sign and symptom. The prognosis is more favorable than conventional osteosarcoma. Also known as: intraosseous well-differentiated osteogenic sarcoma, intraosseous well-differentiated osteosarcoma, low grade intramedullary osteosarcoma, low-grade intramedullary osteosarcoma.