Microvascular Density Does Not Correlate with Histopathology and Outcome in Neuroendocrine Tumors of the Pancreas

Microvascular density (MVD), a marker for tumor angiogenesis, has been demonstrated to have prognostic significance in various malignancies. Previous studies have demonstrated that MVD is an independent prognostic factor in pancreatic adenocarcinoma and that longer survival is associated with hypovascular tumors. The prognostic importance of MVD in pancreatic neuroendocrine tumor (NET) has not been documented. We evaluated MVD in pancreatic NET and correlated it with clinicopathologic features and patient outcome to determine whether MVD is a useful prognostic indicator for these patients. Twenty-five pancreatic NETs from our archival files resected between 1981 and 2000 were identified. The mean MVD was determined for each tumor from the 3 most vascularized 200 × fields. Clinical follow-up ranged from 1 to 19 years, with a mean of 4.9 years. At last follow-up, 6 patients were dead of disease, 10 patients were alive without disease, 4 patients were alive with disease, and 5 patients were alive with disease status unknown. Mean MVD ranged from 43 to 527 microvessels per 200 × field. MVD did not correlate with tumor size, the examined histologic parameters, or patient outcome. MVD in pancreatic NET does not correlate with the clinicohistologic features evaluated in this study or with the patient outcome and is not a useful prognostic indicator in these patients. These results suggest that factors other than the simple number of microvessels are important in determining pancreatic NET behavior. However, most tumors were highly vascular, and additional studies may be helpful to clarify further the role of vascularity and assess the utility of antiangiogenic agents in the treatment of pancreatic NET.