Vascular smooth muscle hyperplasia underlies the formation of glomeruloid vascular structures of glioblastoma multiforme.

The origin of the vascular hyperplasia seen in glioblastoma multiforme is a matter of debate. To test the predominant hypothesis that these glomeruloid structures are of endothelial origin the following study was undertaken. Seven glioblastomas containing prominent glomeruloid vascular structures were stained with Ulex europaeus agglutinin I (UEA-1) and with antibodies against factor VIII/related antigen (fVIII/RAg), glial fibrillary acidic protein (GFAP), S-100 protein, muscle specific alpha-actin (MSA) and smooth muscle specific alpha-actin (SMSA). The GFAP and S-100 antibodies stained the neoplastic glial component of each tumor but did not bind to vascular cells. Endothelial cells lining the lumina of normal vessels and the lumina of glomeruloid vascular structures stained positively with both UEA-1 and fVIII/RAg antibody. No other cells were found to be stained by UEA-1 or by fVIII/RAg antibody. Smooth muscle cells of the normal vasculature stained positively exclusively with anti-MSA and anti-SMSA antibodies. The same pattern of positive actin antibody staining was seen in the majority of cells forming the glomeruloid structures; however, the cells lining the vascular lumina did not bind the MSA and SMSA antibodies. These data strongly suggest that the vascular proliferation resulting in glomeruloid structures is due in large measure to smooth muscle hyperplasia.