4 - Angiogenesis

Abstract

This chapter reviews the role of angiogenesis in pituitary adenomas. Pituitary adenomas are typically slow-growing and histologically benign tumors, but they can become clinically destructive, invade adjacent structures, and recur after treatment. Unlike many other tumors that become aggressive and appear to depend upon angiogenesis in the process, pituitary adenomas tend to do so through nonangiogenic means. Metastatic potential, tumor aggressiveness, overall prognosis, and response to treatment correlate with tumor angiogenesis in a variety of solid tumors. In addition to basic histopathological assessments of angiogenesis, molecular markers of neovascularization are readily apparent in most neoplasms, especially when aggressive phenotypes arise. The process of angiogenesis is the result of a balance between stimulating and inhibiting factors. The recent studies have shown the importance of notch cell-surface receptors and their interaction with various cell membrane ligands in angiogenesis. Abundant angiogenesis in either benign or aggressive pituitary adenomas appears to be generally nonexistent in many of the tumors. It is observed that angiogenesis seems to play a major role in tumor behavior in certain subtypes.