PROLIFERATION OF BONE-TUMORS - AN IMMUNOH ISTOCHEMICAL INVESTIGATION OF KI-67 PROTEIN EXPRESSION

Bone tumors represent a group of tumors of various dignity. In spite o f this single tumor entities may display strong morphological resembla nce to each other which can in turn result in profound difficulties in differential diagnosis. The biological behaviour of a tumor is mainly determined by its rate of proliferation. In this study the rate of pr oliferation of 64 bone tumors (30 high-grade central osteosarcomas, 6 low-grade osteosarcomas, 8 giant cell tumors, 8 aneurysmatic bone cyst s, 5 osteoidosteomas/osteoblastomas, 7 fibrous dysplasias and 5 cases of a myositis ossificans) were analysed. Immunohistochemistry was perf ormed on paraffin-embedded tissue sections using the MIB-1 monoclonal antibody. MIB-1 recognizes the proliferation-associated Ki-67 protein which is expressed during the active phases of the cell cycle but cann ot be detected in senescent cells. Among high-grade central osteosarco mas a significantly higher rate of proliferation (average value 30%) w as found in comparison with low-grade osteosarcomas and other benign i ntraosseous bone tumors. This approach proved to be very useful in the distinction between high-grade and low-grade osteosarcomas as well as bone-forming intraosseous tumors. However distinguishing low-grade os teosarcomas from benign bone tumors by determining only the rate of pr oliferation was not possible, although interestingly, the proliferativ e rate of myositis ossificans, a purely reactive lesion, was in the ra nge of the values determined for high-grade osteosarcoma.