Definition:

Angiosarcomas are rare, generally aggressive, malignant mesenchymal tumours of vascular origin and constitute less than 1% of all sarcomas. Their most frequent site of origin is the head and neck, especially the scalp, of elderly men. Angiosarcomas are likely derived from vascular endothelial cells, possibly resulting from aberrant angiogenesis. Studies have shown relatively increased expression of vascular endothelial growth factor (VEGF) and its receptors (VEGFr1-3) in human angiosarcoma. The most common gene mutation in angiosarcomas is KRAS as well as other RAS mutations. Activation of the RAS pathway is often tumorigenic. Although immortalised murine endothelial cells form benign haemangiomas in vivo, the addition of activated HRAS produces rapidly growing, poorly differentiated angiosarcomas.