Male Breast Cancer: It's All About the Estrogen

Male breast cancer is difficult to study because of its relative rarity compared with breast cancer in women; it is 100-fold more frequent in women. Similar risk factors have been noted for men and women who develop breast cancer, including the effect of hormones manifested by obesity, physical inactivity, diabetes, and exogenous hormone use. In men with Klinefelter syndrome — a condition characterized by the 46-XXY karyotype and an increase risk for breast cancer — gynecomastia and an altered ratio of estrogen to androgens (high) have been reported, highlighting the role of estrogen as a risk factor. There have also been reports suggesting low levels of androgens and excess ratio of estrogen to androgens as risk factors for male breast can…