The incidence of breast cancer has increased steadily in the United States over the past few decades, but breast cancer mortality appears to be declining. This suggests a benefit from early detection and more effective treatment.

The etiology of the vast majority of breast cancer cases is unknown. However, numerous risk factors for the disease have been established.

These risk factors include female gender, increasing patient age, family history of breast cancer at a young age, early menarche, late menopause, older age at first live childbirth, prolonged hormone replacement therapy, previous exposure to therapeutic chest wall irradiation, benign proliferative breast disease, and genetic mutations such as the and genes. However, except for female gender and increasing patient age, these risk factors are associated with only a minority of breast cancers. Women with a strong family history of breast cancer should be evaluated according to the . Women at increased risk for breast cancer (generally those with a greater than 1.67% 5-year risk of breast cancer using the Gail model of risk assessment ) may consider risk reduction strategies (see ).

Proliferative abnormalities of the breast are limited to the lobular and ductal epithelium. In both the lobular and ductal epithelium,a spectrum of proliferative abnormalities may be seen, including hyperplasia, atypical hyperplasia, in situ carcinoma, and invasive carcinoma. Approximately 85% to 90% of invasive carcinomas are ductal in origin. The invasive ductal carcinomas include unusual variants of breast cancer, such as colloid or mucinous, adenoid cystic, and tubular carcinomas, which have especially favorable natural histories.

Some types of food can contribute to the development of cancer; other foods lessen the risk. The following anti-cancer diet greatly lowers your risk of colorectal cancer and nearly all other types of cancers. It can also prevent cardiovascular disease. For people with a genetic tendency toward colorectal cancer, it is not just an option, it's a lifesaving necessity.