Gynecomastia. Immunohistochemical demonstration of estrogen receptors.

Immunohistochemical estrogen receptor (ER) analysis using a monoclonal ER antibody was performed on a total of 30 specimens from 26 patients with gynecomastia. Twenty-six specimens were ER-positive, 3 were ER-negative, and the analysis failed in one case. Immunohistochemical analysis proved more sensitive than biochemical ER analysis in a group of 20 patients, and in a group of 6 patients, the immunohistochemical analysis correlated well with in vitro hormonal sensitivity of the gynecomastic tissue. Semi-quantified ER content was inversely correlated with patient age. There was no relationship between ER content and either histopathologic features or hormonal status. In conclusion, this study demonstrates that the intracellular ER responsible for estrogenic stimulation is present in most gynecomastic tissue specimens, supporting the general assumption that estrogen can be one of the hormones responsible for the development of gynecomastia.