ENG and bone angiosarcoma: Angiosarcomas have high expression levels of endoglin, with 95–100% staining positive.72, 73 Levels of TGF-beta pathway proteins are higher in angiosarcoma of bone than in primary angiosarcomas of soft tissue.74 However, the importance of endoglin in mediating the observed increase in TGF-beta signaling in bone angiosarcoma is not established, and the near universal expression of endoglin in angiosarcomas regardless of their site of origin makes any causative presumptions premature without additional study.