[Review of risk factors for breast cancer--what's new?].

Breast cancer is the most common malignancy in women and constitutes 18% of all cancers in women. Female gender, age and country of birth are the strongest determinants of disease risk. Family history and mutations in tumor suppressor genes BRCA1 and BRCA2 are important correlates of lifetime risk. Genetic polymorphisms associated with estrogen synthesis and metabolism are viewed as major factors in breast cancer prevalence in specific populations. Atypical hyperplasia and ductal/lobular carcinoma in situ although uncommon, are considered as pre-malignant conditions as well as markers for invasive breast cancer. Lately, increased bone density and high breast tissue density on mammogram in postmenopausal women have been reported in association with increased risk of breast carcinoma, probably attributable to increased levels of endogenous estrogen. Serum estrogen levels are higher in breast cancer cases as compared with controls. Current use of oral contraceptives and prolonged, current or recent use of postmenopausal hormonal replacement therapy are also considered as risk factors for breast cancer. Tamoxifen and raloxifene, selective estrogen receptor modulators, were shown to reduce breast cancer risk among high-risk women. Various nutrients were evaluated for their possible effect on breast cancer risk but further studies are needed. High socioeconomic status is found to be associated with increased risk of breast malignancy for as yet unestablished reasons. Studying breast cancer risk factors and further research into the molecular etiology of the disease will enable early diagnosis and detection of high-risk women and ultimately improve prognosis.