Breast cancer is the most common cancer among American women, except for skin cancers. The chance of developing invasive breast cancer at some time in a woman's life is about 1 in 8 (12%).It is estimated that in 2008 about 182,460 new cases of invasive breast cancer will be diagnosed among women in the United States. Women living in North America have the highest rate of breast cancer in the world. At this time there are about 2.5 million breast cancer survivors in the United States.

In addition to invasive breast cancer, carcinoma in situ (CIS) will account for about 67,770 new cases in 2008. CIS is non-invasive and is the earliest form of breast cancer.

Breast cancer incidence rates showed a rapid increase in the 1980s, although the rate of increase slowed in the 1990s compared to the 1980s. After continuously increasing for more than two decades, female breast cancer incidence rates decreased by 3.5% per year from 2001 to 2004. This decrease may reflect the reduced use of hormone replacement therapy (HRT) after the results of the Women's Health Initiative were published in 2002. The study linked HRT use to an increased risk of breast cancer and heart diseases.

Breast cancer is the second leading cause of cancer death in women, exceeded only by lung cancer. The chance that breast cancer will be responsible for a woman's death is about 1 in 35 (about 3%). In 2008, about 40,480 women will die from breast cancer in the United States. Death rates from breast cancer have been declining since about 1990, with larger decreases in women younger than 50. These decreases are believed to be the result of earlier detection through screening and increased awareness, as well as improved treatment.