What Is Breast Cancer?
Breast cancer, the growth of malignant cells in the breast, is the most common cancer among women. It is rare but does occur in men. Breast cancer usually originates in the milk-carrying ducts, although it may arise in the milk-producing lobules or, more rarely, in the dense connective tissue of the breast. There are two major forms of breast cancer:
- Noninvasive carcinoma
- Invasive carcinoma
If cancer cells do not penetrate surrounding tissues and stay within the confines of a duct or lobule, they are called noninvasive, in situ tumors (tumors that remain “in the site” of origin). In situ carcinomas are too small to have formed a “lump” and usually cannot be felt during a physical exam. They are discovered by mammography.
Unfortunately, breast cancers often grow through the basement membrane that surrounds the lobules or ducts. These cancers are termed infiltrating or invasive carcinomas. Roughly 95% of all breast cancers are invasive.
Invasive breast cancers —such as ductal or lobular carcinomas—can gain access to the stroma (supporting tissue) between the ducts, blood vessels, lymphatic vessels, and nerves. Thus, there is a greater chance that cancer will spread throughout the body.
Individuals may develop one, the other, or a combination of invasive and noninvasive breast cancer. If a patient has both types of cancer, treatment is based on the stage of the invasive component.
In 90% of cases, only one breast is affected, although those who have had cancer in one breast are at increased risk of eventually developing it in the other. In all cases, early detection and treatment improve the outlook significantly.
Who Gets Breast Cancer?
In American women, breast cancer is the most common type of cancer, after skin cancers, and the second leading cause of cancer-related deaths. One in eight women in the United States will develop breast cancer during her lifetime.
According to the American Cancer Society (ACS), approximately 230,000 new cases of breast cancer are diagnosed each year in the United States, and the disease causes about 41,000 deaths annually.
The incidence of breast cancer rises after age 40. The highest incidence (approximately 80% of invasive cases) occurs in women over age 50.
- A lump or swelling, usually painless, anywhere in the breast or underarm area (but most commonly in the upper and outer region of the breast).
- Changes in the appearance of the breast’s skin, including flattening, indentation, dimpling, creasing, redness, or scaliness.
- Changes in the nipple, including indentation, an itching or burning sensation, or dark or bloody discharge.
- Changes in the size or symmetry of the breasts.
- Discomfort or pain in the breast in advanced cases.
The precise cause is unknown, but the following factors correlate with a higher incidence of breast cancer:
- Age. The risk of breast cancer increases progressively with age. Most often it occurs after age 50.
- Family history. Approximately 10% of women with breast cancer have a positive family history. Women who have at least 2 first degree relatives with breast cancer that was diagnosed before the age of 50, or ovarian cancer diagnosed at any age, may have inherited one of two breast cancer genes, increasing their risk of both breast and ovarian cancer.
- Having had children late in life or not at all. Women who have no children, have their first child in their 30s, or have never breastfed may be more susceptible to breast cancer.
- Early onset of menstruation (that is before age 11).
- Late menopause (that is not having reached menopause by one’s early 50s).
- Nonmalignant cysts and tumors in the breasts.
- A diet high in animal fat.
- Moderate to severe alcohol intake (greater than 3 drinks per day).
- Possibly, environmental toxins.
- Long-term (greater than 5 years) use of hormone replacement therapy (the combination of estrogen and progestin).
- Long-term nocturnal light exposure (such as shift work).
Diagnosis of breast cancer is made through a process called triple assessment, which includes:
- Clinical examination. During a clinical breast examination, the health care provider examines the breasts (including the nipples and areola) for retractions, skin changes, and discharge. Then, the breasts and underarms are palpated (felt with the fingers). Health care practitioners often teach patients how to perform breast self-examination while doing a clinical examination.
- Imaging procedures. These include mammogram, breast ultrasound, magnetic resonance imaging (MRI scan). During a mammogram, the breast is compressed between two plates for a few seconds and x-rays are taken. Ultrasound (use of sound waves to create an image on a computer screen) may be used to determine if a mass detected by examination or mammogram is a cyst or a solid lesion.
- Biopsy. If a mass is detected by physical examination or mammogram, tissue or fluid may be drawn out of the lump with a needle, or a sample of tissue may be removed during minor surgery and examined.
If a diagnosis of breast cancer is made, the cancer is staged to determine the extent of the disease and course of treatment. The stage of the disease is important to develop an appropriate treatment plan and determine the prognosis (expected outcome of the disease). Staging is based on tumor size, the status of lymph nodes (especially those in the armpit), and whether has metastasized (spread) to other parts of the body.
Treatment for breast cancer depends on the stage of the disease and includes the following:
- Surgery. Surgery combined with radiation and/or chemotherapy is the most common treatment for breast cancer. The type of surgical procedure recommended to the patient depends on the stage of the disease. Mastectomy and lumpectomy are the most commonly performed procedures. If a tumor has invaded the muscle tissue under the breast, the removal of the breast and the underlying muscle tissue (radical mastectomy) may be advised.
- Radiation Therapy. Radiation uses high-energy x-rays to destroy cancer cells. It may be used after surgery to destroy cancer cells that remain in the breast, chest wall, or underarm.
- Chemotherapy. Chemotherapy (treatment by use of chemical substances) may be required before and/or after surgery to prevent further spread of the cancer. Such treatment generally lasts from six months to a year.
- Hormone Therapy. Hormone therapy may be prescribed after surgery for estrogen-receptor-positive tumors. Several drugs, (e.g., tamoxifen and anastrozole), have been developed to treat breast cancer that is responsive to estrogen. Tamoxifen can cause serious side effects, including early stage cancer of the lining of the uterus (this risk increases after 5 years of taking the drug), blood clots and stroke.
- Biological Therapy. Biological therapy (also called immunotherapy) involves using trastuzumab (Herceptin), sometimes in combination with pertuzumab (Perjeta), to inhibit tumor growth and enhance the immune system's ability to fight cancer. It also may be combined with chemotherapy as a first line treatment for metastatic breast cancer and may be used after chemotherapy or anti-estrogen therapy to improve the effectiveness of the treatment. Trastuzumab in combination with pertuzumab is used prior to surgery in some patients.
Reconstructive plastic surgery is available for women who have had part or all of the breast removed. Women may have reconstructive surgery at the same time as surgery to remove the tumor or at a later date.
- Mammograms can detect tumors too small to feel. Women over 50 should have annual mammograms, and those between ages 40 and 50 should discuss their individual risk factors with their doctors to determine when to begin mammography. The exam should be performed by a radiologist specializing in mammography or by a mammography center accredited by the American College of Radiology. A list of accredited centers is available from the National Cancer Institute at 1-800-4-CANCER.
- Women should have a yearly breast exam performed by a doctor or other trained specialist.
- Women should perform monthly breast exams (the best time is two or three days after menstruation ends). Breast tissue is normally somewhat lumpy and uneven, so it is important to become familiar with the normal contour and texture of the breasts. Changes in texture and appearance will then become more easily detectable.
- Regular exercise and maintaining weight can decrease risk of postmenopausal breast cancer.
- Women who are at increased risk of breast cancer may benefit from chemoprevention, the appropriate medication to use should be discussed with a physician. The decision to undergo chemoprevention should be made after discussing individual risks and benefits with a physician.
- Women with a strong family history of breast cancer may consider undergoing genetic testing for one of the breast cancer genes. Women who test positive may undergo increased surveillance for both breast and ovarian cancer or consider preventative removal of their breasts or ovaries.
When To Call Your Doctor
- Make an appointment with a doctor if you notice a lump anywhere in the breast or under the arm. Most lumps are not cancerous, but a biopsy is necessary to diagnose breast cancer with certainty.
- Make an appointment with a doctor if you notice any change in the size, shape, or appearance of the breast or if you experience any discharge from the nipple.
Reviewed by Todd Gersten, M.D., Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network.