Using both immunohisto- and immunocytochemical techniques with
periodate-lysine-paraformaldehyde (PLP) fixation, we have studied the distribution of
Factor VIII-related antigen (FVIIIR:Ag) in 12 cases of
tumors of the human central nervous system (CNS) and one sample of non-
tumor brain tissue. FVIIIR:Ag was found both extracellularly and intracellularly. It was localized in the vascular lumen, between endothelial cells, and in the endothelial cell basement membrane. In the endothelial cell cytoplasm, FVIIIR:Ag was found in the endoplasmic reticulum, perinuclear space, and in intracytoplasmic vacuoles and vesicles. Characteristic of malignant
tumors (six out of seven) was a strongly-positive dilated endoplasmic reticulum. This may reflect increased FVIIIR:Ag synthesis in the endothelial cells of malignant
tumors. Only one of five benign
tumors showed such staining. Six of 12
tumors and the non-
tumor brain showed perinuclear FVIIIR:Ag. Both ad- and abluminal vesicles in the
tumor endothelial cells contained FVIIIR:Ag suggesting that endocytosis, transcellular transport, and/or endocytosis, as well as FVIIIR:Ag synthesis occurs. The non-
tumor brain showed normal capillary structure and very little FVIIIR:Ag immunoreactivity. The relationship of these FVIIIR:Ag abnormalities to the hypercoagulable state seen in some malignant
brain tumor patients remains to be clarified.