PTEN and angiosarcoma: To determine the role of PTEN in the origin or progression of canine hemangiosarcoma, Dickerson et al. [125] firstly examined by immunohistochemistry the expression of CD31 (endothelial marker), PTEN, VEGF, p27 AKt, and p-AKT in sections from 12 haemangiosarcomas and 5 benign splenic haematomas and observed some abnormalities in PTEN expression in the tumours.