Preliminary Data on the Association of Microvessel Density and Vascular Endothelial Growth Factor A in 12 Canine Appendicular Osteosarcoma

Angiogenesis as a prognostic indicator in tumours has been extensively studied, demonstrating a positive correlation for various malignant tumours. Yet, in osteosarcomas (OSAs), its role remains a topic of debate. VEGFA is considered the most important pro-angiogenic factor involved in the development of the vasculature. In order to investigate the possibility that intra-tumoral microvessel density (MVD) expression may be related to VEGFA and may provide useful prognostic information in canine OSA, 12 histological specimens of primary canine appendicular OSA were immunostained using an endothelial marker CD31 and VEGFA antibody. No significant differences in mean MVD were found when comparing with various clinicopathological features, development of pulmonary metastasis and patient prognosis. Notably, the number of vessels counted in VEGFA-High expression specimens was significantly greater than those in the VEGFA-Low expression (p <0.05). In this study, we were able to demonstrate that canine appendicular OSA is a relatively vascular tumour and that the local MVD in primary canine appendicular OSA is significantly correlated with VEGFA immunostaining expression in the tumour tissue. These observations suggest that VEGFA secreted by canine appendicular OSA cells elicits angiogenesis. However, the degree of MVD does not provide prognostic information. It is likely that angiogenesis plays a key role in the tumorigenesis of canine appendicular OSA and may be a potential target for novel anti-angiogenic therapies.