Expression of bone morphogenetic protein and its receptors in osteosarcomaand malignant fibrous histiocytoma

Background: Bone morphogenetic protein (BMP) activity has been found in cas es of malignant fibrous histiocytoma (MFH) and osteosarcoma but only tumors in the latter category show evidence of ossification. The aim of this stud y was to try to understand this difference by examination of the distributi on of BMP and its receptors (BMPR) for this bone inducing protein in these tumors. Methods: Sections of 11 osteosarcoma and 10 MFH were analyzed immunohistoch emically for BMP and BMPRs by use of the avidin-biotin peroxidase method, Results: Nine out of 11 osteosarcoma cases (80.1%) showed positive staining for both BMP and BMPRs. Two cases of chondroblastic type osteosarcoma did not show any significant staining for BMP and BMPRs. In eight out of 10 MFH cases (80%) there was positive staining for BMP. No immunoreactivity for B MPRs was found in any case of MFH, Conclusions: MFH does not express BMPRs and this may be the reason why MFH tumors do not ossify, even in the presence of BMP.