Prognostic Value of Tumor Architecture, Tumor-Associated Vascular Characteristics, and Expression of Angiogenic Molecules in Pancreatic Endocrine Tumors

Abstract

It is difficult to predict the biological behavior of pancreatic endocrine tumors (PETs). Our aim was to evaluate the prognostic significance of certain variables in PETs. The following variables were examined in 37 patients with PETs and then compared with other clinicopathologic characteristics: histologic tumor structure; microvessel density (MVD) measured by three different methods, including a unique method involving calculation of solid area MVD; endothelial proliferation; and the immunohistochemical expression of vascular endothelial growth factor-A and CXC chemokine CXCL-12. Intratumoral vascular structures were analyzed by double immunofluorescence using 30-microm-thick sections. The presence of focal and intensive solid growth of tumor cells (large solid nests; P = 0.003), low solid area MVD (P = 0.002), a high endothelial cell proliferation index (EPI; P = 0.005), and high expression of CXCL-12 in PET cells (P = 0.018) were significant unfavorable prognostic indicators. The predominant structure of the overall tumor histology and the expression of vascular endothelial growth factor-A did not separate aggressive PETs. In areas of focal solid growth, tumor-associated blood vessels had obviously low MVD and high EPI, and their structures were poorly formed with highly abnormal features, in comparison with other areas. High expression of CXCL-12 in tumor cells was significantly associated with variables representing tumor growth, hematogenous tumor spread, low MVD, high EPI, and the presence of large solid nests. This study has provided novel findings on the prognostic features of tumor architecture and tumor-associated angiogenesis in PETs. CXCL-12 is the first candidate molecule in association with neoangiogenesis in PETs.