Angiogenesis in pituitary adenomas and the normal pituitary gland.

Angiogenesis is essential for tumor growth beyond a few millime- ters in diameter, and the intratumoral microvessel count that rep- resents a measure of angiogenesis has been correlated with tumor behavior in a variety of different tumor types. To date no systematic study has assessed pituitary tumors of different secretory types, cor- relating vascular count with tumor size. The vascular densities of pituitary tumors and normal anterior pituitary were therefore as- sessed by counting vessels labeled using the vascular markers CD31 and ulex europaeus agglutinin I. One hundred and twelve surgically removed pituitary adenomas (30 GH-secreting, 25 prolactinomas, 15 ACTH-secreting, and 42 nonfunctioning tumors) were compared with 13 specimens of normal anterior pituitary gland. The vascular counts in the normal anterior pituitary gland were significantly higher (P , 0.05) than those in the tumors using both CD31 and ulex europaeus agglutinin I. In addition, microprolactinomas were significantly less vascular (P , 0.05) than macroprolactinomas, although there was no such difference between vascular densities of microadenomas and macroadenomas producing GH. ACTH-secreting tumors were, like microprolactinomas, of much lower vascular density than the normal pituitary and other secreting and nonsecreting tumor types. In marked contrast to other tumors, pituitary adenomas are less vas- cular than the normal pituitary gland, suggesting that there may be inhibitors of angiogenesis that play an important role in the behavior of these tumors. (J Clin Endocrinol Metab 85: 1159 -1162, 2000)