Proliferation, Vascular Endothelial Growth Factor Expression and Cavernous Sinus Invasion in Growth Hormone Secreting Pituitary Adenomas

Summary  Surgical cure of growth hormone producing pituitary adenomas (GHomas) becomes difficult when they invade the cavernous sinus (CS). Tumour proliferative activity and angiogenesis are thought to be required for tumour growth and invasion, and vascular endothelial growth factor (VEGF) activates neovascularization around tumours. In this study, the mechanism and clinical significance of CS invasion is analysed. In 25 surgically treated GHomas, the extent of CS invasion was classified as high (Knosp's grade 3 and 4), and low (grade 0, 1 and 2) MR grades, and the MR grades were compared with tumour proliferative potential (Ki-67 expression), angiogenetic demand (VEGF expression), volume of adenomas and serum hormone levels.  The Ki-67 index of high MR grade adenomas (1.17±0.62%) was significantly higher than that of low MR grade adenomas (0.55±0.42%, p=0.027), whereas VEGF expression showed no significant correlation with MR grades (p>0.999). Tumour volume also showed a significant correlation with MR grade (p=0.002). VEGF expression was not correlated with serum hormone level and volume, but was correlated with tumour proliferative potential. Proliferative potential and tumour volume were two independent factors related to CS invasion. Although VEGF expression was not a direct factor related to CS invasion, it may indirectly play a role in activation of tumour aggressiveness, which is required in CS invasion.  Our results show that high MR grade adenomas have higher proliferative ability. In order to improve the surgical outcome, pre-operative medical debulking is indicated, particularly, in such adenomas.