VEGFA and angiosarcoma: A minority of angiosarcomas develop pericyte coverage.149 Angiosarcomas that stain positive for alpha-smooth muscle actin (alpha-SMA), a pericyte marker, tend to have positive staining around malignant non-functional vascular channels.149, 150 In physiological vascular regulation, pericytes slow endothelial growth and their loss in other cancer types correlates with increased metastasis.151 In contrast, pericytes derived from less aggressive endothelial cell tumors contribute to the pro-angiogenic microenvironment by constitutive expression of VEGF-A and decreased Ang1 secretion152 (Fig. 3).