ROBO4 and neoplasm: Roundabout 4 (ROBO4) is specifically expressed in vascular endothelial cells and is involved in angiogenesis and the maintenance of blood vessel stability.11, 12 ROBO4 maintains the vascular integrity13 and promotes pathological angiogenesis through various signalling pathways.14, 15ROBO4 is also strongly overexpressed in the vessels of various types of tumours.11, 16 In retinal researches, ROBO4 expression and distribution have been studied in the fibrovascular membranes (FVMs) of patients with proliferative DR.