Estrogen Receptors α and β Immunohistochemical Expression: Clinicopathological Correlations in Pituitary Adenomas

Aim: We investigated the immunohistochemical expression of estrogen receptors alpha (ER alpha) and beta (ER beta) in pituitary adenoma subtypes combined with clinicopathological factors. Materials and Methods: Pituitary adenomas (n=75) were immunostained for ERa and ER beta using the streptavidin-biotin-peroxidase complex method with a monoclonal ERa antibody and polyclonal ER beta antibody. Results: Nuclear immunoreactivity for both receptors was highest among PRL, FSH/LH, null cell, and GH adenomas. ACTH, silent subtypes I and II corticotrophs, and subtype III adenomas were the least immunoreactive for both receptors. ACTH adenomas expressed significantly less ERa than FSH-LH, GH, and null cell adenomas. A significantly elevated ERa expression was observed in macroadenomas compared to microadenomas and non-invasive compared to invasive tumors. Conclusion: ERa and ER beta are differentially expressed in the various pituitary adenoma subtypes suggesting a cell-specific function for these receptors. To elucidate the role of ERa in tumor size and invasiveness, additional studies are required.