Although there was no statistically significant difference in microvessel density between the different groups (P=NS, ANOVA with Bonferroni post hoc correction), the vessels within tumours expressing PAPP-A-resistant IGFBP4 (D), appeared to be of poor quality, with patchy staining suggesting a discontinuous endothelium and expanded cell cytoplasm; vessels were also occluded with no lumen visible, compared with tumours transfected with pCMV (B) or pCMV-BP4 (C). The gene discussed is PAPPA; the disease is neoplasm.