Fig. 4

Differences in microvessel density between tumors with and without venous invasion. The microvessel density (MVD) in tumors with venous invasion was significantly higher compared with that in tumors without venous invasion. MVD was a significant risk factor for venous invasion in hindgut neuroendocrine tumors (Mann–Whitney U test, P < 0.001; values are expressed as the mean ± standard deviation)