Background/Aims: Osteoblastoma and osteosarcoma are primary bone forming
tumors that show different radiological/pathological features and clinical behavior.
This study aims to specify the expression profile of Ki-67 and osteocalcin in
osteoblastomas and osteosarcomas. Methods: Ki-67 and osteocalcin
immunoexpression were studied in 9 osteoblastomas and 30 osteosarcomas;
including 27 osteoblastic osteosarcomas. Results: There was gradual significant
increase (p<0.01) in Ki-67 labeling index (Ki-67-LI) from osteoblastomas (23.7%),
low grade osteosarcomas (58.8%), to high grade osteosarcomas (74.9%). Ki-67-LI
in osteosarcomas was significantly higher than that in osteoblastomas (p<0.001).
Osteocalcin was found in tumor 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: Ki-67 increased ongoing from osteoblastomas
through low grade osteosarcomas, to high grade osteosarcomas and its estimation
may help in the distinction between osteoblastomas and osteosarcomas. Intensity and
distribution of osteocalcin may indicate the degree of osteoblastic differentiation.