Worldwide, breast cancer is the fifth most common cause of cancer death (after lung cancer, stomach cancer, liver cancer, and colon cancer). In 2005, breast cancer caused 502,000 deaths (7% of cancer deaths; almost 1% of all deaths) worldwide. Among women worldwide, breast cancer is the most common cancer.
In the United States, breast cancer is the most prevalent cancer in women, and the second most common cause of cancer death in women (after lung cancer). In 2007, breast cancer is expected to cause 40,910 deaths (7% of cancer deaths; almost 2% of all deaths) in the U.S. Women in the U.S. have 1 in 8 lifetime chance of developing invasive breast cancer and a 1 in 33 chance of breast cancer causing their death.
The number of cases has significantly increased since the 1970s, a phenomenon partly blamed on modern lifestyles in the Western world. Because the breast is composed of identical tissues in males and females, breast cancer also occurs in males, though it is less common.