Home > Conditions & Treatments > Breast Cancer

Breast Cancer

Overview

Breast cancer is the most commonly diagnosed cancer (other than skin cancer) in U.S. women, with more than 190,000 new diagnoses each year.

The suspicion of breast cancer may arise when a lump is detected in the breast or screening mammography reveals an abnormal area of the breast. In order to diagnose the cause of the suspicious area or lump, a physician may perform a biopsy. During a biopsy, a physician removes cells for examination in the laboratory to determine whether cancer is present. Other information obtained from the biopsy sample will play an important role in treatment decisions. If the biopsy indicates that cancer is present, additional surgery may be performed after the patient and doctor select a course of treatment.

Prevention and Screening

The chance of an individual developing cancer depends on both genetic and non-genetic factors. A genetic factor is an inherited, unchangeable trait, whereas a non-genetic factor is a variable in a person’s environment, which can often be changed. Non-genetic factors may include diet, exercise, or exposure to other substances present in our surroundings.

Heredity or Genetic Factors

Being Female: Ninety-nine percent of breast cancer diagnoses in the United States occur in women. Among both women and men, risk of breast cancer increases with age.

Family History: Women with a family history of breast cancer have a greater risk of developing breast cancer themselves. In addition, some families are at particularly high risk of cancer due to hereditary cancer syndromes. These families often have multiple family members with cancer, and are more likely to develop cancer at a young age. In the case of breast and ovarian cancers, inherited mutations in two genes—BRCA1 and BRCA2—have been found to greatly increase the lifetime risk of developing breast and ovarian cancer. Mutations in these genes can be passed down through either the mother’s or the father’s side of the family.

Breast Density: Breast density refers to the extent of glandular and connective tissue in the breast. Breasts with more glandular and connective tissue—and less fat—have greater density. Women with higher breast density are at increased risk of developing breast cancer. In addition, dense breasts make it more difficult to detect breast cancer by mammography.

Personal History of Breast Cancer or Benign Breast Disease: It is important to realize the women who have already had breast cancer are at increased risk for breast cancer in the opposite breast and that this increased risk persists for 20 years or more. Women with certain types of benign breast disease (such as atypical hyperplasia) also have an increased risk of developing breast cancer.

Environmental or Non-Genetic Factors

Reproductive Factors: Several reproductive factors have been associated with an increased incidence of breast cancer. These include an young age at first menstrual period, a late age at menopause, and a late age at the birth of the first child.

Postmenopausal Hormones: Results from the Women’s Health Initiative suggest that postmenopausal hormone therapy with a combination of estrogen and progestin increases the risk of breast cancer. Furthermore, as use of postmenopausal hormones has decreased, breast cancer incidence has also decreased; this provides additional support for a link between postmenopausal hormone use and risk of breast cancer.

Alcohol: Moderate alcohol consumption (often defined as two or more drinks per day) has consistently been linked with an increased risk of breast cancer.

Obesity: In premenopausal women, obesity has been linked with a decreased risk of breast cancer, possibly as a result of disrupted menstrual cycles and altered hormone levels. In postmenopausal women, however, obesity has consistently been linked with an increased risk of breast cancer. The link between obesity and postmenopausal breast cancer appears to be strongest among women who have never used postmenopausal hormone therapy, and may be explained by the higher estrogen levels in obese postmenopausal women. Studies have shown that weight gain in women during adult life increases the risk of postmenopausal breast cancer.

Radiation: Women who have received radiation to the chest for the treatment of Hodgkin’s lymphoma or other cancers appear to have an increased risk of breast cancer. A study has also shown that women who have received low or high dose radiation to the chest have an increased risk of developing breast cancer. Therapeutic doses of radiation have long been known to increase the risk of developing breast cancer. However, this study suggests that diagnostic procedures, such as periodic chest X-rays, can also increase the risk of developing breast cancer.

DES: Diethylstilbestrol (DES) is a synthetic estrogen that was used frequently in pregnant women between the 1940s and 1960s. The drug was used to reduce the risk of miscarriages, though later studies indicated that it probably had no effect on miscarriage risk. In 1971 a study reported that girls born to women who had used DES (DES daughters) had a greatly increased risk of developing a certain type of vaginal cancer. More recent research suggests that DES daughters may also have an increased risk of breast cancer.

Lack of Exercise: Several studies have shown that women who exercise regularly have a lower risk of developing breast cancer than women with less physical activity. One study involving over 100,000 women reported that long-term physical activity reduced the risk breast cancer by one third.

Prevention

Although many questions remain about the causes and prevention of breast cancer, research suggests that certain behaviors are likely to reduce risk.

Limit Alcohol Consumption: Regular alcohol consumption has consistently been linked with a modest increase in risk of breast cancer; by limiting alcohol intake women are likely to reduce their risk of breast cancer as well as several other types of cancer.

Achieve or Maintain a Healthy Body Weight: Excess body weight has been linked with an increased risk of breast cancer in postmenopausal women.24 By achieving or maintaining a healthy weight, women may reduce their risk of breast cancer and other common, chronic health problems.
Engage in Regular Physical Activity: Life-long physical activity is an important component of cancer prevention, and several studies suggest that regular physical activity may decrease the risk of developing breast cancer.

Breastfeed: Long-term breastfeeding has been linked with a modest reduction in breast cancer risk.

Prevention for Women at High Risk

Women with a strong family history of breast cancer and women who carry the BRCA1 and BRCA2 genes have an elevated risk of developing breast cancer and may decide to take more aggressive preventive measures, such as the use of anti-estrogen therapy, prophylactic (preventive) bilateral mastectomy, and/or prophylactic oophorectomy.

Chemoprevention: Drugs that inhibit the effects of estrogen have been shown to reduce the risk of breast cancer in women at high risk of the disease. Two drugs that have been approved for breast cancer risk reduction in certain groups of women are tamoxifen and Evista® (raloxifene). Tamoxifen is approved for breast cancer risk reduction in women who are at high risk of the disease (including high-risk premenopausal women). Evista – originally approved for the prevention and treatment of osteoporosis—is approved for breast cancer risk reduction in postmenopausal women with osteoporosis or postmenopausal women at high risk of breast cancer.

Bilateral Prophylactic Mastectomy (preventive removal of both breasts): Women at high risk of breast cancer may reduce their risk of developing breast cancer by 90% by undergoing bilateral prophylactic mastectomy. Prophylactic mastectomy may decrease concerns about developing breast cancer, but may increase concerns related to self-esteem, sexuality, and femininity. Women considering this procedure need to carefully weight the potential risks and benefits.

Prophylactic Oophorectomy (preventive removal of the ovaries): The BRCA1 and BRCA2 genes increase the risk of both breast and ovarian cancer. Removal of the ovaries before cancer develops reduces the risk of ovarian cancer by about 96 percent. Surgery doesn’t completely eliminate risk because some cells remain behind after surgery. Removal of the ovaries also reduces the risk of breast cancer since some breast cancers don’t grow well without the hormones produced by the ovaries. Women with a BRCA1 or BRCA2 alteration who have had their ovaries removed have about half the risk of developing breast cancer as those who have not had their ovaries removed. Adverse effects of prophylactic oophorectomy include the inability to have children and the development of menopausal symptoms such as hot flashes.

Screening and Early Detection

For several types of cancer, progress in the area of cancer screening has led to earlier cancer detection and better outcomes. The term screening refers to the regular use of certain examinations or tests in persons who do not have any symptoms of a cancer but are at high risk for that cancer.

Mammography: A mammogram is an x-ray image of the breast that can reveal irregularities and help to detect cancer early when it is most treatable. For women at average risk of breast cancer, the U.S. Preventive Services Tasks Force (USPSTF) recommends screening mammography every two years starting at the age of 50. The American Cancer Society, in contrast, continues to recommend annual mammograms starting at the age of 40 for women at average risk. Women who have questions about the screening approach that’s right for them are advised to talk with their doctor. Women at high risk of breast cancer may need to begin screening at an early age.

Clinical Breast Exam: Regular physical examination plays an important role in the health maintenance. An annual gynecological examination is an important screening procedure for several types of cancer and includes a physical examination of the breasts. During this procedure, a healthcare provider physically examines the breasts to feel for any lumps or irregularities.

Magnetic Resonance Imaging (MRI): MRI uses radio waves and a magnet to create detailed images of the inside of the body. The American Cancer Society recommends that women at high risk of breast cancer undergo yearly breast cancer screening with breast MRI in addition to mammography. These recommendations were prompted by several studies of MRI screening of women at high risk of breast cancer. While these studies found that the addition of MRI to mammography increased the frequency of false-positive test results compared with mammography alone, it also produced important improvements in breast cancer detection.

Predictive Genetic Testing: The identification of the breast cancer susceptibility genes BRCA1 and BRCA2 has led to predictive genetic testing for these genes. Since most breast cancers are not due to known inherited mutations, not all women are candidates for genetic testing. Women who appear to be at a high risk, however, may wish to consider being tested for BRCA1 or BRCA2 gene mutations. An accurate genetic test can reveal a genetic mutation, but cannot guarantee that cancer will or will not develop. At this point, genetic tests are used to identify individuals who are at an increased risk of developing cancer, so that these individuals may have the option of taking preventive measures. For more information about genetic testing, please refer to the section Genetic Testing.

Learn More

Patients who have already undergone surgery and lymph node evaluation and know their stage of cancer may select from the options below. In order to learn more about surgery and sentinel lymph node dissection, go to Surgery for Breast Cancer.

Carcinoma In Situ: Noninvasive (Stage 0) disease. This may be ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS).

Stage I: Cancer that is confined to the breast and measures less than 2 cm (about 3/4 inch).

Stage II : Cancer that is less than 5 cm (2 inches) in size and involves axillary lymph nodes, or is greater than 2 cm (3/4 inch) and does not involve axillary lymph nodes.

Stage III: Cancer that involves both a large tumor size and lymph node involvement; more extensive lymph node involvement (such as fixed or matted lymph nodes); or a primary cancer that is attached to the chest wall or skin.

Inflammatory: A rare but aggressive type of breast cancer that may cause the breast to be swollen, red, and warm. The breast may also have a pitted appearance, similar to the skin of an orange.

Stage IV: Cancer that has spread to distant sites in the body.

Recurrent/Relapsed: The breast cancer has progressed or returned after initial treatment.