Plexin domain-containing protein 1 (TEM7) and plexin domain-containing protein 2 (TEM7R) were identified as tumour endothelial markers (TEMs) that displayed elevated expression during tumour angiogenesis. TEM7 encodes a type I transmembrane protein with a large extracellular domain, a hydrophobic transmembrane domain, and a short cytoplasmic tail. Its cell surface expression is essential during endothelial cell capillary morphogenesis.