Evaluation of osteonectin as a diagnostic marker of osteogenic bone tumors

Introduction: Immunohistochemistry plays an important but limited role in the diagnosis of primary bone tumors. Sometimes it is very difficult to differentiate osteosarcomas histologically from other tumors with similar morphology but with different malignant potential and treatment protocol. The correct diagnosis of OSA relies on identification of osteoid production by malignant cells which can be detected by the use of osteonectin. Materials and Methods: The present study was carried out on 200 patients of benign and malignant lesions of bone. After a detailed clinical history and local examination, paraffin section of resected specimens were studied by hematoxylin and eosin and immunohistochemical stain, osteonectin and matrix was graded on a four-tiered grading system with statistical analysis of osteonectin positivity in osteogenic bone tumours and tumour-like lesions. Results: Benign and malignant tumours accounted for 74.6% and 25.0% of the total cases. Osteoid production were seen in 36 cases (100.0%) of osteosarcomas, followed by fibrous dysplasia in 18 cases (100.0%) and osteoid osteoma in 10 cases (100.0%). Both polygonal and spindle shaped tumour cells in osteosarcoma showed Grade 4 positivity with osteonectin. Fibroblastic variant of osteosarcoma showed diffuse (Grade 4) and focal strong staining (Grade 2) alternating with negative areas. Chondroblastic variant of osteosarcoma showed Grade 4+ immunoreactivity in conventional osteosarcoma like areas, whereas chondrocyte- like tumour cells surrounded by chondro-osteoid –like matrix showed well- defined osteonectin staining. Conclusions: Osteonectin is a helpful osteogenic marker for establishing the diagnosis of osteoblastic origin of a tumour that produce no or scarcely any matrix.