BONE MORPHOGENETIC PROTEIN EXPRESSION IN PRIMARY OSSEOUS TUMORS

The expression of bone morphogenetic proteins (BMP) in primary osseous tumors (n=15) with a potential of osteogenesis and/or chondrogenesis was re-evaluated by using a recently characterized monoclonal antibody raised by using rhBMP-2 as an immunogen in a streptavidin-biotin comp lex immunoperoxidase method. The tumors were histopathologically diagn osed as osteosarcoma (n=6), chondrosarcoma (n=3), osteoma (n=2), and c hondroma (n=2). In addition, Ewing's sarcoma (n=2) was also evaluated for comparison. Three distinct categories of immunoreactivity for BMP were observed in osteosarcomas. Firstly, no immunoreactivity in the tu mor cells and tumor osteoid matrices; secondly, immunoreactivity in th e tumor osteoid matrices but not in the tumor cells and lastly, immuno reactivity in the tumor cells but not in the tumor osteoid matrices. T he reactivity was, however, found between the stromal cells and in pri mitive mesenchymal cells. Chondrosarcoma showing proliferating maligna nt chondrocytes with mitosis revealed immunoreactivity for BMP in thei r cytoplasm. Adjacent areas containing no mitotic figures in the chond rocytes showed immunoreactive BMP in the the cartilage matrix while th e tumor cells were unreactive. The chondrogenic areas in osteosarcoma, chondrosarcoma and chondroma showed peripheral regions of chondroid m atrix with immunoreactive BMP. No BMP immunoreactivity was found in Ew ing's sarcoma. BMP as a marker may be useful to identify osteogenic or chondrogenic tumor cells but do not necessarily segregate a benign fr om malignant osteogenic tumors.