TABLE 2.

Histological and immunohistochemical findings

		Vascular Immunohistochemical Features
Tumor Type	Vascular & Glial Morphology	CD31	GFAP	AQ4
metastasis	thin-walled vessels, no astrocytes w/in lesion	positive staining of thin-walled vessel	no staining w/in bulk of lesion, but reconstitution of astrocytic processes at metastasis-brain interface	no staining w/in bulk of lesion, but reconstitution of normal basement membrane at metastasis-brain interface
low-grade glioma	normal-appearing vasculature (endothelial cells), astrocytes w/ normal elongated processes apposing each other & tightly associated w/ the vasculature w/in lesion	positive staining of normal-appearing vasculature w/in region of tumor	staining of astrocytic process tightly associated w/ vessels w/in scattered neoplastic cells w/ dysmorphic nuclei	intense staining surrounding vasculature throughout lesion
malignant glioma* enhancing region	scattered glomeruloid & thick-walled vessels, absence of normal astrocyte architecture	positive staining of thick-walled vasculature, including capillaries	diffuse staining, associated w/ neoplastic cells, no discernible elongated astrocytic processes, gaps in staining surrounding vasculature	diffuse AQ4 staining associated w/ neoplastic cells, gaps of AQ4 staining surrounding vasculature
nonenhancing region	normal-appearing cerebral vasculature, astrocytes w/ normal elongated processes apposing each other & tightly associated w/ vasculature w/in nonenhancing portions of lesion	positive staining of normal- appearing vasculature	staining of glial processes, tightly associated w/ vessels, together w/ scattered staining of neoplastic cells w/ dysmorphic nuclei	intense staining surrounding vasculature throughout lesion

^*Enhancing region: contrast enhancement on MRI after intravenous contrast administration. Nonenhancing region: lack of contrast enhancement on MRI after intravenous contrast administration.