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Role of immunohistochemical cyclo-oxygenase-2 (COX-2) and osteocalcin in differentiating between osteoblastomas and
Zeinab H El-Badawi1, Eman M S Muhammad, Hassan H Noaman
1Department of Pathology, Sohag University, Egypt.
Background/Aims:
Differential diagnosis between aggressive osteoblastoma and low grade osteosarcoma may be very difficult or even impossible on a small biopsy. This study was designed to assess the usefulness of immunoexpression of COX-2 and osteocalcin in the differential diagnosis of the two tumour types.
Methods:
Immunostaining of COX 2 and osteocalcin were studied in 9 osteoblastomas and 30 osteosarcomas.
Results:
All osteoblastomas and 11/20 (55%) high-grade osteosarcomas showed COX-2 immunoreactivity. All low grade osteosarcomas were COX-2 negative. COX-2 was significantly higher (p<0.002) in osteoblastomas 9/9 (100%) than in osteosarcomas 13/30 (43%) and in aggressive osteoblastomas versus low grade osteosarcomas (p<0.01). Osteocalcin was found in tumour cells of all osteosarcomas and osteoblastomas and in the osteoid matrix of 84% of osteosarcomas and 78% of osteoblastomas. Strong osteocalcin was significantly higher (p<0.02) in osteoblastomas (78%) than in osteosarcomas (27%).
Conclusion:
COX-2 is a valuable marker in distinction between osteosarcoma and osteoblastoma. Negative COX-2 could confirm the diagnosis of low grade osteosarcoma versus aggressive osteoblastoma. Intensity and distribution of osteocalcin may indicate the degree of osteoblastic differentiation.
