Health libraryBack to health library
Breast cancer 101
Answers to questions about breast cancer.
Breast cancer starts when cells in the breast become abnormal and start dividing rapidly. According to the American Cancer Society (ACS), most breast cancers start with cells in the milk ducts, the tiny tubes that run from the lobules (glands that make breast milk) to the nipple.
Without effective treatment, these cancer cells continue to multiply, invading and destroying healthy breast tissue and eventually forming a tumor. Cancer cells can also break away from the tumor, travel to other organs and start new tumors.
Early breast cancers usually don't cause symptoms. That's why the ACS recommends regular breast cancer screening. Women age 45 or older should have regular mammograms (specialized x-rays of the breasts).
For women at high risk for breast cancer, the ACS also recommends regular MRIs and talking to a doctor about starting MRIs and mammograms at age 30.
Screening tests may detect breast cancer very early, when simple treatment is most likely to be effective.
If a breast cancer progresses enough to cause symptoms, the most common one is a new lump or mass in the breast, according to the ACS. Breast cancer can also cause swelling, skin irritation, dimpling, redness or scaling on the skin of the breast or nipple, painful nipples, nipple discharge, or a lump in the underarm.
Not all breast lumps are cancer. Most breast lumps are fluid-filled cysts, collections of fibrous tissue or some other type of unusual growth that won't spread beyond the breast and is not life-threatening. Still, any lump or change in a breast should always be checked by a doctor, notes the ACS. You won't be able to tell the difference between harmless and dangerous changes on your own.
According to the ACS, risk factors for breast cancer include:
- Older age. Most breast cancers are found in women age 55 or older.
- Family history. Women whose mother, sister or daughter had breast cancer are at higher risk themselves.
- Genetics. Women who have mutated forms of some genes have a higher risk for breast cancer.
- History of breast cancer. Women who have had cancer in one breast are more likely to develop cancer in the other breast.
- Race. White women are more likely than women of other races to develop breast cancer.
- Past radiation treatment. Women who have had radiation therapy to the chest are at higher risk for breast cancer.
- Age of first and last period. Women who started menstruating before age 12, or stopped menstruating after age 55, are at higher risk for breast cancer.
- Past pregnancies. In general, women who have no biological children or did not bear children until after age 30 have a higher risk for breast cancer.
- DES (diethylstilbestrol). Women who were given this drug during pregnancy have a higher risk for breast cancer.
- Medicines with hormones. Birth control pills and hormone therapy after menopause have both been linked to increased breast cancer risk.
- Obesity and being overweight. Women who are overweight or obese after menopause are more likely to develop breast cancer than those who maintain a healthy weight.
- An inactive lifestyle. Women who get regular exercise are less likely to develop breast cancer.
- Alcohol. As little as one alcoholic drink a day can raise a woman's breast cancer risk.
Breast cancer may be found during a screening test such as a mammogram, an MRI or a breast exam or when a woman notices a lump, tender spot or other breast change either by accident or during a breast self-exam. If your doctor thinks there's any chance that it's cancer, he or she will order additional tests. These may include specialized imaging tests and a biopsy. A biopsy is the only way to confirm that cancer is present, according to the ACS. It involves removing a sample of tissue and inspecting it under a microscope to look for signs of cancer.
Breast cancer may be treated with surgery, radiation therapy, chemotherapy, hormone therapy, immunotherapy or a combination of these treatments, according to the ACS. Treatment decisions are generally made by considering the type and stage of the cancer, general health and personal preferences. Every treatment option has benefits and drawbacks.
When breast cancer is found early, it can almost always be treated successfully, according to the ACS. Breast cancer that isn't detected and treated until it has spread to distant parts of the body is more difficult to treat and has a poorer outlook.
You can reduce your risk of developing breast cancer by not drinking alcohol, getting regular exercise and maintaining a healthy body weight, according to the ACS. Also talk to your doctor about the screening schedule that's right for you, so if cancer does develop you're more likely to detect it very early.
If you have a strong family history of breast cancer, you may want to talk to your doctor about other options for breast cancer prevention. Medicines or (in rare cases) surgery may be used to reduce risk in very high-risk women, notes the ACS.
According to the ACS, breast exams—done either by yourself or a health professional—aren't recommended because they don't show a clear benefit. However, you should be familiar with how your breasts look and feel. When you know what's normal for you, changes may be more likely to stand out if they do happen. You should report any changes to a healthcare provider immediately.