Osteonectin in osteosarcomas: a marker for differential diagnosis and/or prognosis? Seventy-five osteosarcomas at various grades of histologic differentiation were investigated for evidence of osteonectin. According to the results of the study, osteonectin was present in all osteosarcomas. An association between the intensity of the osteonectin antibody reaction and prognosis could not be established. Evidence of osteonectin was also found in other bone tumors. Osteonectin is therefore unsuitable for differential diagnosis, cannot be regarded as a bone specific protein and has not prognostic value.