Vascularity in Nontumorous Human Pituitaries and Incidental Microadenomas: A Morphometric Study.

The aim of the present study was to determine the microvascular angioarchitecture in the lateral and central portions of the anterior lobe as well as of the posterior lobe. The possible association between vascularity and age, sex, and pregnancy was also examined. In addition the vascular density of incidental microadenomas was investigated and compared to that of nontumorous gland. Blood vessels of 120 nontumorous pituitaries and 11 incidental microadenomas obtained at autopsy were examined by immunohistochemistry using the endothelial marker CD 34. Microvascular density (MVD) and microvessel surface density (MSD) were determined by morphometry using an automatic computer image analysis system. MVD and MSD were higher in the anterior than in the posterior lobe. Age, gender, or pregnancy did not affect the angioarchitecture of these sites. No statistical differences in MVD and MSD were observed between central and lateral areas of the anterior lobe, although MVD appeared to be lower in the lateral zones. A marked difference was noted in the vascularity of microadenomas compared to nontumorus tissue; both MVD and MSD were significantly lower in adenomatous tissue. Our studies suggest that the capillary network of the anterior and posterior lobes differ. They also indicate that the microvascular architecture is not significantly affected by age, gender, or pregnancy. Lack of significant angiogenesis in pituitary microadenomas may underlie the low growth rate and infrequency of metastasis of pituitary adenomas.