Aromatase and steroid receptors in gynecomastia and male breast carcinoma: an immunohistochemical study.

Hormonal factors have been implicated in the development of male breast disorders, including carcinoma and gynecomastia. We studied the expression of aromatase and estrogen (ER), progesterone (PR), and androgen (AR) receptors by immunohistochemistry in male breast carcinoma (15 cases) and gynecomastia (30 cases) to evaluate their possible significance in these disorders. Relatively strong aromatase immunoreactivity was observed in all cases of carcinoma, but in only 11 of 30 cases (37%) of gynecomastia. ER and PR expression was observed in the nuclei of ductal cells in all the cases of gynecomastia. More than 10% of the carcinoma cells were positive for ER and PR in 9 of 15 (60%) and 10 of 15 (67%) carcinomas, respectively. AR immunoreactivity was observed in nuclei of both epithelial and non-epithelial cells. AR was present in ductal or carcinoma cells in 13 of 15 (87%) cases of carcinoma and in all 30 (100%) cases of gynecomastia. The mean percentage of ER-, PR-, and AR-positive cells were significantly higher in gynecomastia than in carcinoma. There was a close association of AR with ER (P < 0.01) and PR (P < 0.01) in cases of gynecomastia, but there was a significant inverse correlation between AR and ER (P < 0.01) or PR (P < 0.05) expression in carcinoma cases. Increased aromatase expression in the stromal cells is considered to contribute to the increment in the in situ estrogen concentration and the development of male breast carcinoma.