What is breast cancer?
Cells in the body normally divide (reproduce) only when new cells are needed. Sometimes, cells in a part of the body grow and divide out of control, which creates a mass of tissue called a tumor. If the cells that are growing out of control are normal cells, the tumor is called benign (not cancerous). If, however, the cells that are growing out of control are abnormal and don't function like the body's normal cells, the tumor is called malignant (cancerous).
Cancers are named after the part of the body from which they originate. Breast cancer originates in the breast tissue. Like other cancers, breast cancer can invade and grow into the tissue surrounding the breast. It can also travel to other parts of the body and form new tumors, a process called metastasis.
Who gets breast cancer?
Breast cancer is the most common cancer among women other than skin cancer. Increasing age is the most common risk factor for developing breast cancer, with 66% of breast cancer patients being diagnosed after the age of 55.
In the US, breast cancer is the second-leading cause of cancer death in women after lung cancer, and it's the leading cause of cancer death among women ages 35 to 54. Only 5 to 10% of breast cancers occur in women with a clearly defined genetic predisposition for the disease. The majority of breast cancer cases are "sporadic,” meaning there is no definitive gene mutation.
Does breast cancer affect women of all races equally?
All women, especially as they age, are at some risk for developing breast cancer. The risks for breast cancer in general aren’t evenly spread among ethnic groups, and the risk varies among ethnic groups for different types of breast cancer. Breast cancer mortality rates in the United States have declined by 40% since 1989, but disparities persist and are widening between non-Hispanic Black women and non-Hispanic white women.
Statistics show that, overall, non-Hispanic white women have a slightly higher chance of developing breast cancer than women of any other race/ethnicity. The incidence rate for non-Hispanic Black women is almost as high.
Non-Hispanic Black women in the U.S. have a 39% higher risk of dying from breast cancer at any age. They are twice as likely to get triple-negative breast cancer as white women. This type of cancer is especially aggressive and difficult to treat. However, it's really among women with hormone positive disease where Black women have worse clinical outcomes despite comparable systemic therapy. Non-Hispanic Black women are less likely to receive standard treatments. Additionally, there is increasing data on discontinuation of adjuvant hormonal therapy by those who are poor and underinsured.
In women under the age of 45, breast cancer is found more often in non-Hispanic Black women than in non-Hispanic white women.
Women who are Asian, Hispanic and Native American are at lower risk of developing and dying of breast cancer. However, women who are of Ashkenazi Jewish (Eastern European) descent are at higher risk for developing breast cancer because they have a higher rate of BRCA mutations.
Non-Hispanic white women and Asian/Pacific Islander women are more likely to be diagnosed at an earlier stage (localized disease) than women of other ethnic/racial groups.
Does a benign breast condition mean that I have a higher risk of getting breast cancer?
Benign breast conditions rarely increase your risk of breast cancer. Some women have biopsies that show a condition called hyperplasia (excessive cell growth). This condition increases your risk only slightly.
When the biopsy shows hyperplasia and abnormal cells, which is a condition called atypical hyperplasia, your risk of breast cancer increases somewhat more. Atypical hyperplasia occurs in about 5% of benign breast biopsies.
What are the types of breast cancer?
The most common types of breast cancer are:
- Infiltrating (invasive) ductal carcinoma. This cancer starts in the milk ducts of the breast. It then breaks through the wall of the duct and invades the surrounding tissue in the breast. This is the most common form of breast cancer, accounting for 80% of cases.
- Ductal carcinoma in situ is ductal carcinoma in its earliest stage, or precancerous (stage 0). In situ refers to the fact that the cancer hasn't spread beyond its point of origin. In this case, the disease is confined to the milk ducts and has not invaded nearby breast tissue. If untreated, ductal carcinoma in situ may become invasive cancer. It is almost always curable.
- Infiltrating (invasive) lobular carcinoma. This cancer begins in the lobules of the breast where breast milk is produced, but has spread to surrounding tissues in the breast. It accounts for 10 to 15% of breast cancers. This cancer can be more difficult to diagnose with mammograms.
- Lobular carcinoma in situ is a marker for cancer that is only in the lobules of the breast. It isn't a true cancer, but serves as a marker for the increased risk of developing breast cancer later, possibly in both or either breasts. Thus, it is important for women with lobular carcinoma in situ to have regular clinical breast exams and mammograms.
What is invasive breast cancer?
Invasive breast cancer occurs when cells spread beyond the ducts or lobules. These cells first invade the surrounding breast tissue, and can possibly travel to the lymph nodes.
What is non-invasive breast cancer?
With non-invasive breast cancer, the cancer cells are confined to the ducts or lobules. This is also known as carcinoma in-situ. Ductal carcinoma in-situ (DCIS) is when the ductal cells divide abnormally, but stay within the ducts.
Can cancer form in other parts of the breast?
Cancers can also form in other parts of the breast, but these types of cancer are less common. These can include:
- Angiosarcomas. This type of cancer begins in the cells that make up the lining of blood or lymph vessels. These cancers can start in breast tissue or breast skin. They are rare.
- Inflammatory breast cancer. This type of cancer is rare and different from other types of breast cancer. It is caused by obstructive cancer cells in the skin’s lymph vessels.
- Paget disease of the breast, also known as Paget disease of the nipple. This cancer affects the skin of the nipple and areola (the skin around the nipple).
- Phyllodes tumors. These are rare, and most of these masses are not cancer. However, some are cancerous. These tumors begin in the breast’s connective tissue, which is called the stroma.
What are the stages of breast cancer?
There are two different staging systems for breast cancer. One is called “anatomic staging” while the other is “prognostic staging”. The anatomic staging is defined by the areas of the body where the breast cancer is found and helps to define appropriate treatment. The prognostic staging helps medical professionals communicate how likely a patient is to be cured of the cancer assuming that all appropriate treatment is given.
The anatomic staging system is as follows:
Stage 0 breast disease is when the disease is localized to the milk ducts (ductal carcinoma in situ).
Stage I breast cancer is smaller than 2 cm across and hasn't spread anywhere — including no involvement in the lymph nodes.
Stage II breast cancer is one of the following:
- The tumor is less than 2 cm across but has spread to the underarm lymph nodes (IIA).
- The tumor is between 2 and 5 cm (with or without spread to the lymph nodes).
- The tumor is larger than 5 cm and has not spread to the lymph nodes under the arm (both IIB).
Stage III breast cancer is also called "locally advanced breast cancer." The tumor is any size with cancerous lymph nodes that adhere to one another or to surrounding tissue (IIIA). Stage IIIB breast cancer is a tumor of any size that has spread to the skin, chest wall, or internal mammary lymph nodes (located beneath the breast and inside the chest).
Stage IV breast cancer is defined as a tumor, regardless of size, that has spread to areas away from the breast, such as bones, lungs, liver or brain.
Symptoms and Causes
What causes breast cancer?
We do not know what causes breast cancer, although we do know that certain risk factors may put you at higher risk of developing it. A woman's age, genetic factors, family history, personal health history, and diet all contribute to breast cancer risk.
What are the risk factors for breast cancer?
Like many conditions, risk factors for breast cancer fall into the categories of things you can control and things that you cannot control. Risk factors affect your chances of getting a disease, but having a risk factor does not mean that you are guaranteed to get a certain disease.
Controllable risk factors for breast cancer
- Alcohol consumption. The risk of breast cancer increases with the amount of alcohol consumed. For instance, women who consume two or three alcoholic beverages daily have an approximately 20% higher risk of getting breast cancer than women who do not drink at all.
- Body weight. Being obese is a risk factor for breast cancer. It is important to eat a healthy diet and exercise regularly.
- Breast implants. Having silicone breast implants and resulting scar tissue make it harder to distinguish problems on regular mammograms. It is best to have a few more images (called implant displacement views) to improve the examination. There is also a rare cancer called anaplastic large cell lymphoma (ALCL) that is associated with the implants.
- Choosing not to breastfeed. Not breastfeeding can raise the risk.
- Using hormone-based prescriptions. This includes using hormone replacement therapy during menopause for more than five years and taking certain types of birth control pills.
Non-controllable risk factors for breast cancer
- Being a woman. Although men do get breast cancer, it is far more common in women.
- Breast density. You are at higher risk of breast cancer if you have dense breasts. It can also make it harder to see tumors during mammograms.
- Getting older. Aging is a factor. A majority of new breast cancer diagnoses come after the age of 55.
- Reproductive factors. These include getting your period before age 12, entering menopause after age 55, having no children, or having your first child after 30.
- Exposure to radiation. This type of exposure could result from having many fluoroscopy X-rays or from being treated with radiation to the chest area.
- Having a family history of breast cancer, or having genetic mutations related to certain types of breast cancer. Family history that includes having a first degree relative (mother, sister, daughter, father, brother, son) with breast cancer poses a higher risk for you. If you have more than one relative on either side of your family with breast cancer, you have a higher risk. In terms of genetic mutations, these include changes to genes like BRCA1 and BRCA2.
- Having already had breast cancer. The risk is higher for you if you have already had breast cancer and/or certain types of benign breast conditions such as lobular carcinoma in situ, ductal carcinoma in situ, or atypical hyperplasia.
- Exposure to diethylstilbestrol (DES). DES was prescribed to some pregnant women in the United States during 1940-1971. If you took DES, or your mother took DES, you have a higher risk of breast cancer.
What are the warning signs of breast cancer?
- A lump or thickening in or near the breast or in the underarm that persists through the menstrual cycle.
- A mass or lump, which may feel as small as a pea.
- A change in the size, shape, or contour of the breast.
- A blood-stained or clear fluid discharge from the nipple.
- A change in the look or feel of the skin on the breast or nipple (dimpled, puckered, scaly, or inflamed).
- Redness of the skin on the breast or nipple.
- An area that is distinctly different from any other area on either breast.
- A marble-like hardened area under the skin.
These changes may be found when performing monthly breast self-exams. By performing breast self-exams, you can become familiar with the normal monthly changes in your breasts.
Breast self-examination should be performed at the same time each month, three to five days after your menstrual period ends. If you have stopped menstruating, perform the exam on the same day of each month.
Diagnosis and Tests
How is breast cancer diagnosed?
During your regular physical examination, your doctor will take a thorough personal and family medical history. He or she will also perform and/or order one or more of the following:
- Breast examination: During the breast exam, the doctor will carefully feel the lump and the tissue around it. Breast cancer usually feels different (in size, texture, and movement) than benign lumps.
- Digital mammography: An X-ray test of the breast can give important information about a breast lump. This is an X-ray image of the breast and is digitally recorded into a computer rather than on a film. This is generally the standard of care (vs. analog mammogram).
- Ultrasonography: This test uses sound waves to detect the character of a breast lump — whether it is a fluid-filled cyst (not cancerous) or a solid mass (which may or may not be cancerous). This may be performed along with the mammogram.
Based on the results of these tests, your doctor may or may not request a biopsy to get a sample of the breast mass cells or tissue. Biopsies are performed using surgery or needles.
After the sample is removed, it is sent to a lab for testing. A pathologist — a doctor who specializes in diagnosing abnormal tissue changes — views the sample under a microscope and looks for abnormal cell shapes or growth patterns. When cancer is present, the pathologist can tell what kind of cancer it is (ductal or lobular carcinoma) and whether it has spread beyond the ducts or lobules (invasive).
Laboratory tests, such as hormone receptor tests (estrogen and progesterone) and human epidermal growth factor receptor (HER2/neu), can show whether hormones or growth factors are helping the cancer grow. If the test results show that they are (a positive test), the cancer is likely to respond to hormonal treatment or antibody treatment. These therapies deprive the cancer of the estrogen hormone or use a monoclonal antibody known as herceptin to treat the cancer.
Breast cancer diagnosis and treatment are best accomplished by a team of experts working together with the patient. Each patient needs to evaluate the advantages and limitations of each type of treatment and work with her team of physicians to develop the best approach.
Other diagnostic tests
Other methods being investigated include:
- Scintimammography: A technique in which radioactive contrast agents are injected into a vein in the arm. An image of the breast is taken with a special camera, which detects the radiation (gamma rays) emitted by the dye. Tumor cells, which contain more blood vessels than benign tissue, collect more of the dye and project a brighter image.
- Positron emission tomography (PET) scanning: A technique that measures a signal from injected radioactive tracers that migrate to the rapidly dividing cancer cells. The PET scanner picks up the signal and creates an image.
- Magnetic resonance imaging (MRI): A test that produces very clear pictures, or images, of the human body without the use of X-rays. MRI uses a large magnet, radio waves, and a computer to produce these images.
Management and Treatment
How is breast cancer treated?
If the tests find cancer, you and your doctor will develop a treatment plan to eradicate the breast cancer, to reduce the chance of cancer returning in the breast, as well as to reduce the chance of the cancer traveling to a location outside of the breast. Treatment generally follows within a few weeks after the diagnosis.
The type of treatment recommended will depend on the size and location of the tumor in the breast, the results of lab tests done on the cancer cells, and the stage, or extent, of the disease. Your doctor will usually consider your age and general health as well as your feelings about the treatment options.
Breast cancer treatments are local or systemic. Local treatments are used to remove, destroy, or control the cancer cells in a specific area, such as the breast. Surgery and radiation treatment are local treatments. Systemic treatments are used to destroy or control cancer cells all over the body. Chemotherapy and hormone therapy are systemic treatments. A patient may have just one form of treatment or a combination, depending on her individual diagnosis.
Surgery: Breast conservation surgery involves removing the cancerous portion of the breast and an area of normal tissue surrounding the cancer, while striving to preserve the normal appearance of the breast. This procedure has often been called a lumpectomy, also referred to as a partial mastectomy. Typically, some of the lymph nodes, either in the breast and/or under the arm are also removed for evaluation. Usually, six weeks of radiation therapy is then used to treat the remaining breast tissue. Most women who have a small, early-stage tumor are excellent candidates for this approach.
Mastectomy (removal of the entire breast) is another option. The mastectomy procedures performed today are not the same as the older, radical mastectomies. Radical mastectomies were extensive procedures that involved removing the breast tissue, skin, and chest-wall muscles. Today, mastectomy procedures do not ordinarily remove muscles and, for many women, mastectomies are accompanied by either immediate or delayed breast reconstruction.
What happens after the local breast cancer treatment?
Following local breast cancer treatment, the treatment team will determine the likelihood that the cancer will recur outside the breast. This team usually includes a medical oncologist, a specialist trained in using medicines to treat breast cancer. The medical oncologist, who works with the surgeon, may advise the use of the drugs like tamoxifen or anastrozole (ARIMIDEX®) or possibly chemotherapy. These treatments are used in addition to, but not in place of, local breast cancer treatment with surgery and/or radiation therapy.
After treatment for breast cancer, it is especially important for a woman to continue to do a monthly breast examination. Regular examinations will help you detect local recurrences. Early signs of recurrence can be noted in the incision area itself, the opposite breast, the axilla (armpit), or supraclavicular region (above the collar bone).
Maintaining your follow-up schedule with your physician is also necessary so problems can be detected when treatment can be most effective. Your health care provider will also be able to answer any questions you may have about breast self-examination after the following procedures.
Breast Examination After Treatment for Breast Cancer
The incision line (scar) may be thick, raised, red and possibly tender for several months after surgery. Remember to examine the entire incision line.
If there is redness in areas away from the scar, contact your physician. It is not unusual to experience brief discomforts and sensations in the breast or nipple area (even if the nipple has been removed).
At first, you may not know how to interpret what you feel, but soon you will become familiar with what is now normal for you.
After breast reconstruction
Following breast reconstruction, breast examination for the reconstructed breast is done exactly the same way as for the natural breast. If an implant was used for the reconstruction, press firmly inward at the edges of the implant to feel the ribs beneath. If your own tissue was used for the reconstruction, understand that you may feel some numbness and tightness in your breast. In time, some feeling in your breasts may return.
After radiation therapy
After radiation therapy, you may notice some changes in the breast tissue. The breast may look red or sunburned and may become irritated or inflamed. Once therapy is stopped, the redness will disappear and the breast will become less inflamed or irritated. At times, the skin can become more inflamed for a few days after treatment and then gradually improve after a few weeks. The pores in the skin over the breast also may become larger than usual.
Some women have different sensations in the breast because of changes in skin sensitivity. You may feel numbness or tingling in the breast, or feel that the breast is more sensitive to clothing or tight garments. After radiation therapy, the breast may become smaller. Normally within a year after radiation therapy, most of the changes will improve.
During radiation therapy, you should continue with monthly self-examinations of the radiated breast as well as the other breast. If you notice any new developments, call your health care provider.
What to do
By immediately reporting any suspicious changes to your physician, you will not only receive early treatment if necessary, but you will also resolve your own fear and anxiety. Most breast lumps (about 80 percent) are benign. However, your self-examination may lead you to the early detection of a new or recurrent cancer. The earlier the diagnosis, the better the chances for successful therapy.
How can I protect myself from breast cancer?
Follow these three steps for early detection:
- Get a mammogram. The American Cancer Society recommends having a baseline mammogram at age 35, and a screening mammogram every year after age 40. Mammograms are an important part of your health history. Recently, the US Preventive Services Task Force (USPTF) came out with new recommendations regarding when and how often one should have mammograms. These include starting at age 50 and having them every two years. We do not agree with this, but we are in agreement with the American Cancer Society and have not changed our guidelines, which recommend yearly mammograms starting at age 40.
- Examine your breasts each month after age 20. You will become familiar with the contours and feel of your breasts and will be more alert to changes.
- Have your breast examined by a healthcare provider at least once every three years after age 20, and every year after age 40. Clinical breast exams can detect lumps that may not be detected by mammogram.
Can exercise help reduce my risk of developing breast cancer?
Exercise is a big part of a healthy lifestyle. It can also be a useful way to reduce your risk of developing breast cancer in your postmenopausal years. Women often gain weight and body fat during menopause. People with higher amounts of body fat can be at a higher risk of breast cancer. However, by reducing your body fat through exercise, you may be able to lower your risk of developing breast cancer.
The general recommendation for regular exercise is about 150 minutes each week. This would mean that you work out for about 30 minutes, five days each week. However, doubling the amount of weekly exercise to 300 minutes (60 minutes, five days each week) can greatly benefit postmenopausal women. The longer duration of exercise allows for you to burn more fat and improve your heart and lung function.
The type of exercise you do can vary — the main goal is get your heart rate up as you exercise. It’s recommended that your heart rate is raised about 65 to 75% of your maximum heart rate during exercise. You can figure out your maximum heart rate by subtracting your current age from 220. If you are 65, for example, your maximum heart rate is 155.
Aerobic exercise is a great way to improve your heart and lung function, as well as burn fat. Some aerobic exercises you can try include:
Pick an activity you enjoy and want to do over and over again. The more you like your activity, the more likely you’ll be to continue exercising day-after-day. You don’t have to do the same activity for all 300 minutes of your weekly exercise. You can mix it up and try different things throughout the week. The important thing is to keep moving.
Remember, there are many benefits to working more exercise into your weekly routine. Some benefits of aerobic exercise can include:
- Lower cholesterol and blood pressure.
- Increased endurance.
- A lower resting heart rate.
- Weight loss or maintenance of your current weight.
- Stress relief.
- Improved sleep.
Always talk to your healthcare provider before starting a new diet or exercise routine. It’s important to know if you have any limitations before you start exercising. Having an open and honest conversation about your exercise goals can help your provider guide you as you develop a fitness plan.
How do tamoxifen, raloxifene, anastrozole, and exemestane reduce the risk of breast cancer?
If you are at increased risk for developing breast cancer, four medications — tamoxifen (Nolvadex®), raloxifene (Evista®), anastrozole (Arimidex®), and exemestane (Aromasin®) — may help reduce your risk of developing this disease. These medications act only to reduce the risk of a specific type of breast cancer called estrogen receptor-positive breast cancer. This type of breast cancer accounts for about two-thirds of all breast cancers.
Tamoxifen and raloxifene are in a class of drugs called selective estrogen receptor modulators (SERMs). These drugs work by blocking the effects of estrogen in breast tissue by attaching to estrogen receptors in breast cells. Because SERMs bind to receptors, estrogen is blocked from binding. Estrogen is the fuel that makes most breast cancer cells grow. Blocking estrogen prevents estrogen from triggering the development of estrogen-receptor-positive breast cancer.
Anastrozole and exemestane are in a class of drugs called aromatase inhibitors (AIs). These drugs work by blocking the production of estrogen. Aromatase inhibitors do this by blocking the activity of an enzyme called aromatase, which is needed to make estrogen.
How much do tamoxifen and raloxifene lower the risk of breast cancer?
Multiple studies have shown that both tamoxifen and raloxifene can reduce the risk of developing estrogen receptor-positive breast cancer in healthy postmenopausal women who are at high risk of developing the disease. Tamoxifen lowered the risk by 50 percent. Raloxifene lowered the risk by 38 percent. Overall, the combined results of these studies showed that taking tamoxifen or raloxifene daily for five years reduced the risk of developing breast cancer by at least one-third. In one trial directly comparing tamoxifen with raloxifene, raloxifene was found to be slightly less effective than tamoxifen for preventing breast cancer.
Both tamoxifen and raloxifene have been approved for use to reduce the risk of developing breast cancer in women at high risk of the disease. Tamoxifen is approved for use in both premenopausal women and postmenopausal women (women who have not had a period for one full year). Raloxifene is approved for use only in postmenopausal women.
Less common but more serious side effects of tamoxifen and raloxifene include blood clots to the lungs or legs. Other serious side effects of tamoxifen are an increased risk for cataracts and endometrial cancers. Other common, less serious shared side effects of tamoxifen and raloxifene include hot flashes, night sweats, and vaginal dryness.
How much do anastrozole and exemestane lower the risk of breast cancer?
Studies have shown that both anastrozole and exemestane can lower the risk of breast cancer in postmenopausal women who are at increased risk of the disease.
In one large study, taking anastrozole for five years lowered the risk of developing estrogen receptor-positive breast cancer by 53 percent. In another study, taking exemestane for three years lowered the risk of developing estrogen receptor-positive breast cancer by 65 percent.
The most common side effects seen with anastrazole and exemestane are joint pains, decreased bone density, and symptoms of menopause (such as hot flashes, night sweats, vaginal dryness).