An approximation of 1% vascularity within these tumours is based on the ratio of brown pixels (CD31 stain) in a section to blue pixels (nuclei) that had a median of 0.72% IQR = 0.5–1.0 in our SW480 xenografts [22] and in other colorectal cancer xenografts [29,30]. This evidence concerns the gene PECAM1 and colorectal cancer.