Pretreatment of sections (enzymatic digestion, heating), endothelial markers (vWF-von Willebrand factor and CD31 antibodies), method of quantification (highest microvascular density, average microvascular density and microvascular volume) and inter-observer variations were all found to alter the estimated vascularity and interestingly the treatment of sections before staining was the variable that most significantly altered the calculated vascularity of tumours (Schor et al, 1998). This evidence concerns the gene VWF and neoplasm.