Role of exogenous and endogenous sources of estrogen on the incidence of breast fibroadenoma: case-control study in Iran.

Breast fibroadenoma (FAD) is the most common benign mammary condition among women but the environmental risk factors have not identified yet. As the role of long term estrogen exposure in the incidence of FAD has been remained controversial; we have decided to investigate the possible role of endogenous and exogenous sources of estrogens in present study. Women less than 45 years old who underwent surgery from June 2009 to June 2010 were matched with controls by age and hospital. From reproductive factors, lack of breast feeding (p< 0.001, 8.76 CI95% 3.79-20.24), Nulliparity (p=0.001, OR=8.09, CI95% 3.505-18.67), Lack of parity (p=0.001, OR=6.64, CI 95% 2.56-16.31) and Hormonal dysfunction (p=0.016, OR=4.66, CI 95% 1.26- 17.28) were considered as the most important ones. Adiposity and abnormal weight gain after 18 years were considered as major background factor which induce FAD and may be contributed to the level of endogenous estrogen. Out of evaluated exogenous sources of estrogen, lower age at first OCP consumption (20.76_+3.87 vs. 22.85_+3.88, p=0.046) and living near Polycyclic aromatic hydrocarbons (PAHs) producing factories (p< 0.001, OR=3.7, CI95%1.61-7.94), were considered as the main sources of exposure to xenestrogens in FAD patients but FAD showed inverse association with cigarette smoking because of antiestrogenic activities of cigarette smoking . This study concludes that the incidence and development of FAD could be associated with the reproductive history of women, activity of ovarian hormones as well as environmental factors.