Angiogenesis in pituitary adenomas and the normal pituitary gland

Angiogenesis is essential for tumor growth beyond a few millimeters in diam eter, and the intratumoral microvessel count that represents a measure of a ngiogenesis has been correlated with tumor behavior in a variety of differe nt tumor types. To date no systematic study has assessed pituitary tumors o f different secretory types, correlating vascular count with tumor size. Th e vascular densities of pituitary tumors and normal anterior pituitary were therefore assessed by counting vessels labeled using the vascular markers CD31 and ulex europaeus agglutinin I. One hundred and twelve surgically rem oved pituitary adenomas (30 GH-secreting, 25 prolactinomas, 15 ACTH-secreti ng, and 42 nonfunctioning tumors) were compared with 13 specimens of normal anterior pituitary gland. The vascular counts in the normal anterior pitui tary gland were significantly higher (P < 0.05) than those in the tumors us ing both CD31 and ulex europaeus agglutinin I. In addition, microprolactino mas were significantly less vascular (P ( 0.05) than macroprolactinomas, al though there was no such difference between vascular densities of microaden omas and macroadenomas producing GH. ACTH-secreting tumors were, like micro prolactinomas, 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 vascular than the normal pituitary glan d, suggesting that there may be inhibitors of angiogenesis that play an imp ortant role in the behavior of these tumors.