Endocan, a new invasion and angiogenesis marker of pituitary adenomas

Angiogenesis plays a crucial role in tumor growth. Recently, endocan has emerged as a new marker of vascular endothelial cells from cancers in other organs. In this study, we elucidated the relationship between endocan expression and tumor invasion of pituitary adenoma. Tumor tissues were obtained from 70 patients with pituitary adenoma and were examined using fluorescence immunohistochemistry. Tissue samples included 4 adrenocorticotrophic hormone producing adenomas, 10 growth hormone-producing adenomas, 49 clinically nonfunctioning adenomas, 6 prolactin producing adenomas, and 1 thyroid-stimulating hormone producing adenoma. Endocan was exclusively expressed in CD34-positive vascular endothelial cells, with over 90 % colocalization. The CD34 expression was significantly elevated with endocan expression (linear regression slope, 1.200; r(2) = 0.268, F = 23.08, p < 0.0001). As a percentage of CD34 expression, endocan expression was elevated in a Knosp grading dependent manner (Spearman's r-value, 0.651; p < 0.0001), and was also significantly elevated in macroadenomas compared with microadenomas (p = 0.0133). However, no differences in endocan expression were observed between hormonal subtypes (p = 0.066; Kruskal-Wallis test), age (Spearman's rank correlation test, p = 0.4909), or sex (Mann-Whitney test, p = 0.1701). These data show that endocan is closely related to tumor angiogenesis, and may predict tumor invasion into neighboring cavernous sinuses in pituitary adenomas.