The redox-regulatory CD31 function linked to YAP signaling was determined using a CD31-blocking antibody and siRNA approach and was further validated in CD31-knockout endothelial cells.<b>Results:</b> We found that most angiosarcomas contain a small CD31<sup>low</sup> cell population.
Primary gastric epithelioid angiosarcomas: the definitive diagnosis was provided by immunohistochemical analysis with endothelial markers such as cluster of differentiation 31 (CD31), ether-a-go-go-related gene (ERG), and Freund leukemia integration (FLI-1).
CD31 immunostaining demonstrated that the human malignant vascular tumors Kaposi's sarcoma and angiosarcoma were filled with capillary-like structures, whereas in benign cavernous and capillary hemangiomas, blood vessels were not as abundantly present.
However, trephine biopsy revealed formation of anastomosing vascular spaces by the tumor cells and immunoreactivity for CD31, supporting a diagnosis of angiosarcoma.
Our findings suggest that CD31 and CD34 are useful in defining endothelial differentiation in poorly differentiated angiosarcomas in which reactions for Ulex europeus lectin type I and factor VIII-related antigen may be equivocal.