Mucinous colon carcinomas with microsatellite instability have a lower microvessel density and lower vascular endothelial growth factor expression.

We determined the association between cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF) expression, microvessel density (MVD) and microsatellite instability (MSI) or the histological type in colon adenocarcinomas. Sixty-six cases were studied, 28 MSI+ and 38 MSI-. MSI phenotype was determined using polymerase chain reaction. MVD was assessed after CD31 staining in ten x400 fields (0.96 mm(2)) in the most vascularized areas. VEGF and COX-2 expression were studied by means of immunohistochemistry. MVD positively correlated with the levels of VEGF expression (P=10(-4)) and also with the levels of COX-2 expression (P=0.007). MVD and VEGF expression were lower in MSI+ carcinomas (P=0.002 and P=0.03 respectively). When mucinous tumors were excluded from the statistical analysis, the association between low MVD, low VEGF and MSI status disappeared (P=0.5, P=1, respectively). MSI+ mucinous carcinomas had a lower MVD and VEGF expression than other MSI+ carcinomas (P=0.008 and P=0.004, respectively) and MSI- mucinous carcinomas (P=0.01 and P=0.001, respectively). COX-2 expression was lower in medullary carcinomas (P=0.001). In conclusion, mucinous MSI+ colon carcinomas represent a special group of colon adenocarcinomas relating to angiogenesis, with a lower MVD and VEGF expression than both MSI- mucinous carcinomas and MSI+ non-mucinous carcinomas. A low COX-2 expression could be related to the medullary phenotype. However, this has to be confirmed in a larger series. Finally, the low MVD of MSI+ mucinous colon adenocarcinomas could participate in their overall better prognosis.