What Is Breast Cancer? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Breast cancer is a disease that starts in the breast with a malignant tumor. A malignant tumor is a mass of cells that grows out of control. The cancerous cells can also metastasize, or move to other tissues or parts of the body.

The cancer can develop in any of the three types of breast tissue: lobules, ducts, and connective tissue.

Most cancer begins in the lobules (the milk-producing glands), or in the ducts, along which milk travels to the nipple. (1) But tumors can also develop in the fibrous and fatty connective tissue that surrounds the lobules and ducts.

Several different types of breast cancer exist. The type of breast cancer and its stage, or how far it has grown, determine the treatment for it.

Breast cancer that spreads into normal tissue is called invasive breast cancer. Noninvasive breast cancer stays within the breast lobule or duct. (2)

If you notice any of the following symptoms, check in with your healthcare provider. (3,4)

• Any lump in or near the breast or underarm
• Warmth or unexplained tenderness in the breast
• A hardening, thickening, or swelling area in the breast
• Nipple tenderness without another cause
• Nipple discharge (except breast milk), especially clear or bloody discharge
• An unexplained change in color, texture, size, or shape of the breasts or nipples
• Skin dimpling on the breast or enlarged pores (like an orange skin)
• Swelling, redness, scaliness or general pain in the breast or nipples
• Nipples that turn inward without explanation
• Irritated or itchy breasts
• A rash on the breast, which can be a sign of inflammatory breast cancer

While a lump can be a sign of cancer, nearly 80 percent of lumps found in the breast turn out to be noncancerous. (5) The most common causes of noncancerous lumps include:

• Fibrocystic changes as a result of hormonal fluctuations
• Cysts
• Benign lumps called fibroadenomas
• Wart-like growths called intraductal papillomas
• Fatty tissue that occurs as a result of trauma to the breast

The biggest risk factors for this disease, besides female sex, include:

• Age — risk starts to rise after age 50
• A family history
• Genetics
• Previous exposure to radiation

Each woman’s risk involves a combination of different factors. If you’re concerned, your doctor can help you assess how great your risk is, and whether you need to take any extra precautions with regard to screening. (6)

Genetic Testing for Breast Cancer: BRCA1 and BRCA2

In some cases, particularly if you have a family history of breast or ovarian cancer, a doctor may suggest genetic testing for two of the most common gene mutations known to increase risk for developing these cancers: BRCA1 and BRCA2. Inherited BRCA gene mutations cause about 5 to 10 percent of breast cancers and about 10 to 15 percent of ovarian cancers. (7) There are other genes implicated in breast cancer risk, though they are much rarer than the BRCA mutations.

Learn More About Causes of Breast Cancer: Common Risk Factors, Genetics, and More

Doctors can screen for breast cancer using a mammogram. A mammogram is an X-ray with low-dose radiation that lets doctors look for abnormalities in the breast tissue.

Doctors may also screen for breast cancer with magnetic resonance imaging (MRI), ultrasound, or 3D mammography (called breast tomosynthesis).

An MRI uses a large magnet to create images of the breast. An ultrasound sends sound waves into the breast that create an image when they bounce back. A 3D mammogram uses X-rays like a regular mammogram, but it takes multiple image slices of the breast at different angles to construct a 3D image. (8)

Screening tests look for possible signs of breast cancer but cannot diagnose it. If doctors see a suspicious lump or mass of cells, they may use some of those same tests to get a closer look at the abnormal area. A diagnostic mammogram provides more detail in the image of the breast. (9)

The only way to make a certain diagnosis of breast cancer is a biopsy. A biopsy involves removing some breast tissue or fluid from the suspicious area and looking at the cells under a microscope. (10)

Finding Your Best Treatment Team

After receiving a diagnosis, you will have several decisions to make about the healthcare providers who will handle your treatment.

Cancer treatment usually involves a team of people, such as a surgeon, a medical oncologist, a nurse practitioner, a counselor, a patient navigator, and specialists associated with your cancer type.

Factors to consider in choosing your oncologist and treatment team are their expertise in your cancer type, what your insurance will cover, your ability to travel to and from appointments and procedures, and recommendations from others.

Even after you have a treatment team, it is a good idea to look for another oncologist to get a second opinion on your diagnosis and treatment options. It is acceptable and sometimes common to change doctors during your treatment if you need to.

Learn More About Diagnosing Breast Cancer: Tests and Screenings, Early Diagnosis, and Your Doctors

Breast Cancer Stages 0–4

Doctors use stages of breast cancer to describe how far along the cancer has grown or spread. Stages range from 0 to 4 (often expressed in Roman numerals, I–IV). Each stage has further subcategories of A, B, or C. (11)

Stage 0 The cancer is noninvasive and shows no evidence of leaving the part of the breast where it began. One type of stage 0 cancer is ductal carcinoma in situ (DCIS).

Stage 1 The cancer cells are spreading to surrounding breast tissue, but the group of cancer cells or the tumor remains very small. It is usually easily treatable.

Stage 2 The cancer has begun to grow but it remains only in the breast or nearby lymph nodes. Treatment is not usually very difficult.

Stage 3 The cancer has begun invading lymph nodes, muscle, and other body tissue near the breast, but it has not reached organs farther away. Treatments vary according to the person and type of breast cancer.

Stage 4 The cancer is very advanced and has spread to several organs or other parts of the body. Stage 4 breast cancer is considered incurable, but women may live several years or more with ongoing treatment.

Learn More About Breast Cancer Staging

Different Types of Breast Cancer and Precancer

DCIS/LCIS: The Slow-Moving Breast Cancers

A biopsy may reveal a noninvasive cancer that is not growing beyond its starting location. These types of cancers are called carcinoma in situ. (12)

"Carcinoma" refers to a cancer that begins in the outer layer of cells around an organ. “In situ” means something stays where it began.

Ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS) are the two types of in situ carcinoma in the breast. Doctors usually find DCIS or LCIS on a mammogram or other imaging because they rarely have signs or symptoms. (13)

DCIS means abnormal cells exist in the lining of the milk ducts but have not invaded surrounding breast tissue. DCIS can become invasive cancer if not treated. (14)

LCIS occurs in the breast lobules, where breast milk is produced, without spreading further. LCIS is not technically cancer, but it is sometimes called precancerous. (13)

LCIS is less common than DCIS but indicates a higher risk of invasive cancer. LCIS may not require treatment beyond observation to see whether breast cancer develops. (13)

Learn More About DCIS/LCIS

Invasive Breast Cancer

Invasive (or infiltrative) ductal carcinoma (IDC) is the most common type of breast cancer and the type most likely to occur in men. It makes up 80 percent of all new breast cancer cases and becomes more common with older age. (15)

Like DCIS, IDC begins in the milk ducts, but it spreads beyond the ducts into the surrounding fatty tissue. It may continue to spread into the lymph nodes and bloodstream.

Treatment for IDC will depend on the stage, the type of breast cancer, its aggressiveness, and other characteristics. Treatment generally consists of some combination of surgery, radiation, chemotherapy, targeted therapy, hormone therapy, and immunotherapy.

Learn More About Treating Invasive Ductal Carcinoma

Triple Negative and HER-2 Negative Breast Cancer

A subset of women diagnosed with breast cancer will be told that their tumor is triple negative, which means that the cells within the tumor lack receptors on their surface that respond to human epidermal growth factor receptor 2 (HER-2) as well as estrogen and progesterone receptors. (16)

What does that mean? Some of the drugs used to treat breast cancer, which are designed to interact with these receptors, won’t be useful in these cases. Doctors will need to tailor a treatment regimen to other weaknesses in this tumor type.

Learn More About Triple Negative and HER-2 Negative Breast Cancer

Prognosis of Breast Cancer

Prognosis depends on the stage of breast cancer and the general health of any given individual. But broadly, rates of death from breast cancer have been decreasing. The majority of women survive this cancer. Overall, 90 percent of women will survive at least five years after being diagnosed with breast cancer. (17) As of January 2020, more than 3.5 million women in the United States have a history with breast cancer. (18)

How long does breast cancer last? There's no simple answer. Different treatment plans follow different timetables. Depending on your individual needs, it may be necessary to take time off from work — to recover from surgery or a cycle of chemotherapy. (19)

Recurrent breast cancer is breast cancer that returns after initial treatment; it may occur months or years after your initial treatment. (20) The highest risk of recurrence is during the first two years after treatment, though the majority of patients won't experience recurrence. (21)

There's currently no cure for metastatic breast cancer (stage 4 breast cancer that has spread to other parts of the body) but with treatment to control it, many patients with the disease now live productive, fulfilling lives for years. (22)

A treatment plan will depend on what type and stage of breast cancer you have, and how aggressive it is.

Breast cancer is most commonly treated with surgery, often accompanied by treatments to help rid the body of cancer cells, or to ensure that it remains cancer-free. (23)

Surgical treatments include lumpectomy, in which a small portion of the breast (where the tumor is located) is removed. If more tissue needs to be removed, your surgeon will perform a partial mastectomy.

A mastectomy is the removal of one or both breasts and may include removal of lymph nodes and armpit tissue.

Along with surgery, radiation may be used to kill cancer cells that remain in the area.

Most women who have had all or part of a breast removed can have reconstructive surgery for their breast (or breasts), to match the size and shape of the other breast or their original breasts.

Medication Options

A range of medications, involved in chemotherapy, hormone therapy, and biologic targeted therapy, may be used to treat breast cancer. These medication regimens are considered systemic treatment, since they affect cells throughout the body. (23)

Chemotherapy involves a combination of drugs used to destroy cancer cells or slow their growth. Chemotherapy can be given before or after breast cancer surgery.

Your doctor will determine if chemotherapy is right for you based on the type and size of tumor you have, the degree to which your lymph nodes are involved, and the risk of cancer spreading.

If your type of cancer is found to be sensitive to hormones, you may need hormone therapy, which interferes with the body's ability to produce or use hormones, in order to slow or stop the growth of tumors.

Hormone therapy for cancer is not the same as hormone therapy for menopause.

Hormone therapy treatments include medications called selective estrogen receptor modulators (SERMs), which block hormones from attaching to cancer cells; aromatase inhibitors, which stop the body from making estrogen after menopause; and Faslodex (fulvestrant), which targets estrogen receptors for destruction. (24)

Removal of the ovaries or medications that stop the ovaries from making estrogen may also be recommended.

Biologic targeted therapy uses drugs that can alter the behavior of breast cancer cells.

Immunotherapy uses medications to stimulate the body's immune response in order to recognize and eliminate cancer cells. Immunotherapy may be used for some forms of breast cancer. (25)

Alternative and Complementary Therapies

In addition to medical interventions, you may want to consider complementary therapies, particularly to help manage symptoms as well as side effects from treatment.

Acupuncture, massage, meditation, mindfulness, and visualization may help reduce stress and anxiety, relieve pain, and improve mood.

Learn More About Treatment for Breast Cancer: Medication, Alternative and Complementary Therapies, Surgery Options and More

Diet and Breast Cancer: Is There a Right Way to Eat?

A healthy diet helps your body remain strong while you undergo breast cancer treatments. Your diet can help your body rebuild damaged tissue, reduce therapy side effects, or reduce the risk of infection. (26 PDF)

A healthy diet includes a variety of vegetables, fruits, whole grains, dairy, and lean, high-protein foods, such as chicken, fish, legumes, and beans. It is important to get enough calories each day even if you don’t feel like eating.

Some breast cancer treatments may have side effects that make it difficult to eat well. These side effects may include nausea, vomiting, constipation, diarrhea, dehydration, a sore mouth or throat, weight gain, or changes to your sense of taste or smell. (27)

Your doctor can help you identify strategies to treat these side effects, reduce their impact, and find ways to eat as healthfully as possible despite the effects.

Foods to avoid during breast cancer treatment include alcohol, fried or greasy foods, and foods with high amounts of fat or sugar.

Learn More About Diet and Cancer

Breast Cancer Doesn’t Mean Give Up Your Gym Membership

There was a time when women with breast cancer were told to rest, and exercise was an afterthought. But a growing body of research suggests that a reasonable exercise program not only won’t hurt, it might actually benefit patients by relieving treatment-related fatigue, reducing the risk of lymphedema (a painful buildup of fluid in the lymph nodes) and improve cognitive function, which many women say can be impaired by treatment.

Learn More About Exercise and Cancer

Prevention of Breast Cancer

While you can't change certain risk factors, such as your family history or your age, research shows there are a number of lifestyle modifications you can make to reduce your risk of breast cancer, even if you're high risk.

Limit yourself to less than one alcoholic drink a day and don't smoke.

Control your weight — being overweight or obese increases your risk of breast cancer, particularly after menopause. Exercise can help you maintain a healthy weight. The American Cancer Society recommends that adults get 150 to 300 minutes of moderate intensity or 75 to 150 minutes of vigorous intensity activity each week, ideally spread throughout the week. (28)

Women who breastfeed for at least several months may also lower their risk. (28)

Hormone therapy to alleviate symptoms during menopause can increase your risk for breast cancer. Consider nonhormonal options or use the lowest dose that works for you. (29)

Try to avoid exposure to radiation and environmental pollution. Medical-imaging methods, such as computerized tomography, use high doses of radiation. While more studies are needed, some research suggests a link between breast cancer and cumulative exposure to radiation over your lifetime. Reduce your exposure by having such tests only when absolutely necessary.

Women who are at an increased risk of breast cancer — because of a family history or because genetic testing has revealed a mutation in the BRCA1 or BRCA2 gene — should opt for closer monitoring by their healthcare provider and consider taking certain medications that may reduce the risk in certain high-risk women. For women with a very high risk, preventive surgery is an option to consider. (28)

As with treatment, possible complications of breast cancer depend on the type and stage of breast cancer you have. A number of the complications are side effects from treatment, that continue after treatment stops. Depending on what kind of treatment you've had, these can include: (30)

• Fatigue
• Headaches
• Osteoporosis
• Blood clots
• Heart problems
• Infertility
• Menopausal symptoms
• Dental issues

Some patients develop a chronic condition called lymphedema, following treatment. Lymphatic fluid accumulates in the tissues, causing swelling. Lymphedema usually results from removal of or damage to lymph nodes. (31)

Breast cancer makes up about 30 percent of new cancer diagnoses in women. (18) But the rate of breast cancer cases began dropping in the year 2000 and has continued declining since.

About one in eight women (about 12.4 percent of all women) will be diagnosed with invasive breast cancer at some point in their lives. (2) Breast cancer can occur in anyone with breast tissue, but it’s much rarer in men than in women.

The disease is more common in middle age. About one in four breast cancer cases occur in women between ages 55 and 64.

The incidence of breast cancer overall is only slightly higher for white women than Black women, but in women under 45, breast cancer is more common in Black women. Black women are also more likely to die from breast cancer than women of other races or ethnicities. (18) At least some of this increased risk is due to less access to follow-up care after an abnormal mammogram and lower rates of health insurance. (32)

Ovarian Cancer

Most breast and ovarian cancers are not caused by genetic mutations, but mutations in the BRCA 1 and BRCA2 genes, which increase the risk of breast cancer, also increase the risk for ovarian cancer in women. (33) Women with a family history of both these cancers may want to consider genetic testing. (34)

Periodontal Disease

Research has suggested a connection between periodontal disease (gum disease) and breast cancer. In a meta-analysis of studies, published in December 2018 in the journal Frontiers in Oncology, study authors concluded that periodontal disease may be a potential risk factor for the development of breast cancer among women, and that effective periodontal therapy could serve as a valuable preventive measure against breast cancer. (35)

People with breast cancer will likely need several types of support. This can include emotional support and resources such as counseling, support groups, online groups, and advocacy organizations. (36)

You may also need financial assistance, informational resources, help with travel arrangements for treatment, help identifying appropriate doctors and treatment teams, and recovery resources.

Learn More About Additional Resources and Support for Breast Cancer