Platelet-derived growth factor receptor (beta-subunit) immunoreactivity in soft tissue tumors.

Using a well characterized monoclonal antibody (PR7212) to the beta-subunit of the platelet-derived growth factor receptor (PDGF-R(beta) and the avidin-biotin peroxidase method on frozen sections, we analyzed PDGF-R(beta) expression in 71 nonepithelial lesions as well as normal mesenchymal tissues. PDGF-R(beta) reactivity was observed in normal salivary gland, normal cutaneous and visceral fibroblasts, muscularis mucosa of bowel, and endothelial cells; squamous carcinoma was negative. Interestingly, hepatocytes and lymph node histiocytes were also positive. Positive tumors included malignant fibrous histiocytoma (6/6), benign and malignant smooth muscle tumors (5/6 leiomyoma, 8/9 leiomyosarcoma), liposarcoma (4/4), synovial sarcoma (6/7), angiosarcoma (2/2), and sarcoma NOS (2/2). Fibromatosis cases were also positive (2/2). In many tumors, the reactive fibroblasts and vascular components were also reactive. The characteristic pattern of reactivity in fibroblastic lesions highlighted thin cytoplasmic extensions or strands not visible in normal hematoxylin and eosin-stained sections. Expression of PDGF-R(beta) was not necessarily correlated with the presence of PDGF. We conclude that PDGF-R(beta) expression can be identified in a wide variety of mesenchymal lesions and postulate that its presence may be important in the mechanism of growth of these tumors.