Bone Morphogenetic Protein Expression in Primary Osseous Tumors.

Abstract

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 complex immunoperoxidase method. The tumors were histopathologically diagnosed as osteosarcoma (n=6), chondrosarcoma (n=3), osteoma (n=2), and chondroma 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 tumor cells and tumor osteoid matrices; secondly, immunoreactivity in the tumor osteoid matrices but not in the tumor cells and lastly, immunoreactivity in the tumor cells but not in the tumor osteoid matrices. The reactivity was, however, found between the stromal cells and in primitive mesenchymal cells. Chondrosarcoma showing proliferating malignant chondrocytes with mitosis revealed immunoreactivity for BMP in their cytoplasm. Adjacent areas containing no mitotic figures in the chondrocytes showed immunoreactive BMP in the the cartilage matrix while the tumor cells were unreactive. The chondrogenic areas in osteosarcoma, chondrosarcoma and chondroma showed peripheral regions of chondroid matrix with immunoreactive BMP. No BMP immunoreactivity was found in Ewing's sarcoma. BMP as a marker may be useful to identify osteogenic or chondrogenic tumor cells but do not necessarily segregate a benign from malignant osteogenic tumors.