Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) and its receptor flt-1 in microcystic meningiomas

We investigated the immunohistochemical expression of vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) and of its endothelial cell receptor flt-1 in relationship to microcyst formation in meningiomas. Expression of VPF/VEGF was studied in 60 meningiomas (6 microcystic, 38 partially microcystic and 16 with no microcystic areas) and 30 meningiomas from these three subgroups were evaluated for flt-1 expression. VPF/VEGF immunoreactivity was mainly observed in vessel endothelium. Positive vessels were present in 75% (33/44) of meningiomas with any amount of microcystic pattern and in 38% (6/16) of the solid meningiomas (P < 0.02). Densities and percentages of both VPF/VEGF-positive and flt-1-positive vessels were higher in meningiomas with microcystic areas than in solid meningiomas (P≤ 0.002). The 6 microcystic meningiomas showed the highest densities and percentages of both VPF/VEGF-positive (P≤ 0.0002) and flt-1-positive vessels (P≤ 0.01). Vessel expression of VPF/VEGF and flt-1 were positively correlated (r≥ 0.75, P < 0.0001). A strong positive correlation between VPF/VEGF-positive vessel density and proportion of microcystic pattern in all 60 specimens was found (r = 0.75, P < 0.0001). We conclude that accumulation of flt-1-bound VPF/VEGF on endothelial cells of meningiomas is associated with microcyst formation that leads to the histologic appearance of microcystic meningiomas.