The breast, or mammary gland, is a fibrofatty organ that produces all the necessary nutrients for a newborn. In women of childbearing age, the breast responds to cyclic hormone production and contains an abundance of epithelial structures and stroma that enable the production of milk. In postmenopausal women, declining ovarian function in late menopause leads to regression of these structures. The postmenopausal breast contains a ductal system, but the lobules shrink and collapse, leaving an organ that is composed primarily of fat. While a breast lump in a premenopausal woman is likely to be a benign problem related to cyclic hormonal changes, in a postmenopausal woman, this is not the case and the most important breast disease is cancer.
Cancer is the leading cause of death in women aged 55 to 74 years and is second to heart disease in women aged 75 and older. The incidence of cancer increases dramatically with age. In particular, breast cancer—the most common cancer in American women—is a major health concern. According to 2007 American Cancer Society estimates, breast cancer is the most common cancer in women, accounting for 31% of all newly diagnosed malignancies (178 480 new cases) and the second leading cause of cancer-related death (40 460 deaths). Moreover, U.S. incidence and mortality data from the 1980s suggest that 12% of all women will be diagnosed with breast cancer during their lifetime and that 3.5% will die from it.
Approximately half of the cases of breast cancer occur in women older than age 65 years. In addition, 1999 National Vital Statistics indicate that the incidence increases dramatically with age (Figure 95-1) from an invasive breast cancer rate of 15 per 1000 in women aged 40 to 50 years to a rate of 43 per 1000 in women aged 70 to 80 years. Older age has also been associated with a lower breast cancer specific survival rate (Figure 95-1).
Breast cancer incidence and mortality by age.
Breast cancer is a major health concern and will become of even greater importance as the size of the older population grows. Although breast cancer is more common in older women, they are also less likely to be appropriately screened, more likely to present for care at a more advanced stage and to receive inferior surgical and postoperative management, and are less likely to be entered into clinical trials.
The specific cause of breast cancer is unknown. Many factors associated with increased risk have been identified. These include the following: increasing age, white race, family history of breast cancer (especially in a first-degree relative), early menarche, late age at birth of first child (older than 30 years), late menopause, history of benign breast disease (hyperplasia or atypical hyperplasia), heavy radiation exposure, obesity, increasing height, postmenopausal estrogen replacement therapy, and moderate to ...