What Is Breast Cancer?

Cancer is a disease that is characterized by abnormal cell growth. These cancer cells can form tumors and spread to surrounding tissue. When this process originates in the breast, it’s known as breast cancer.

In the United States, breast cancer is the second most common cancer in women, following skin cancer. Although it’s much less common, men can develop breast cancer too. Over 260,000 women and 2,400 men are diagnosed with breast cancer each year.

Most breast cancers begin in the tube-shaped ducts of the breast. In female breasts, these ducts connect the milk-producing glands (called lobules) to the nipples; male breasts have these ducts and a few glands too—though they usually don’t produce milk. Less often, breast cancers may originate in the lobules and more rarely, in the breast’s fatty and fibrous connective tissue.

If the cancer spreads to other tissues and organs in the body, it’s called metastatic breast cancer.

Due to early screening and diagnosis, along with better treatments for breast cancer, female deaths from breast cancer have declined by over 40% between 1989 and 2019.

From 2015 to 2019, the U.S. Cancer Statistics reports that the death rate is about 20 out of every 100,000 women with breast cancer.

It’s important to learn about the risk factors and prevention for breast cancer and what you can expect from diagnosis and treatments.

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Types

There are several types of breast cancer, categorized by where the cancer starts and where it has spread. Some common breast cancers are:

• Ductal carcinoma in situ (DCIS): This is an early-stage cancer in the ducts of the breast. It is non-invasive, meaning it hasn’t spread to other parts of the body. It has a high survival rate of 95% from 10 years of diagnosis.
• Invasive ductal carcinoma (IDC): Also called infiltrating ductal carcinoma, this is the most common type of breast cancer. It begins in the lining of the duct and spreads to other breast tissue. As an invasive cancer, it can spread to other parts of the body through your bloodstream or lymphatic system (part of your immune system).
• Invasive lobular carcinoma (ILC): This is an invasive cancer that begins in the lobules and spreads to surrounding tissue.

Some breast cancers are rare. Inflammatory breast cancer (IBC), for example, is an uncommon-but-aggressive form. It tends to occur in women younger than 40.

A doctor can classify breast cancers by their stage, based on:

• Tumor size and location
• Number and location of affected lymph nodes (organs that help your body fight infection)
• Metastasis (the spread of cancer cells to other tissues and/or organs)​​
• Tumor grade (how fast a tumor grows, based on how abnormal the cells are)
• Estrogen receptor and progesterone receptor status (whether cancer cells produce these hormone-specific proteins)
• HER2 (human epidermal growth factor receptor 2) status, a protein that speeds up breast cancer growth

Based on the type of cancer, an oncologist (a doctor specializing in cancer diagnosis and treatment) can determine a suitable treatment plan.

For male breast cancer, it may be difficult to detect in the breast tissue alone. A healthcare provider may also take scans of other parts of the body, like the chest and abdomen to determine the cancer stage.

Symptoms

Breast cancer symptoms vary, and many people have no symptoms at all, especially early on. That's why regular screening mammograms are so important. Mammograms are a type of X-ray that may detect small tumors before you can feel them.

Still, mammography isn't foolproof; you should also become familiar with your breasts, so you know what is and isn’t normal for you.

Pay attention to any breast changes you experience, including these possible warning signs:

• A new lump in the breast or armpit
• Changes in the size or shape of the breast (swelling, thickening, or shrinkage)
• Skin dimpling or pitting (like an orange peel)
• Red, dry, flaking, or thickened nipple or breast skin
• Breast or nipple pain
• A nipple that turns inward or has a sore
• Milky or bloody discharge from the nipple
• Swollen lymph nodes under the armpit or around the collarbone

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Causes

Breast cancer begins when mutated cells in the breast divide and grow without restraint. These abnormal cells form a mass of tissue called a tumor. There are a variety of reasons as to why this may occur. For some people, you may have inherited gene mutations (passed down through families) that can harm your cells’ ability to fix DNA mutations. More often, your cells can become cancerous even if you don’t have a genetic risk for breast cancer—perhaps due to certain lifestyle or environmental factors.

Risk Factors

Though breast cancer is most common in people assigned female at birth, several factors may raise your risk of breast cancer, regardless of your sex. These include:

• Being age 50 or older
• Being overweight or obese, especially when also at an older age
• Inheriting certain genes (such as BRCA1 and BRCA2)
• A family history of breast cancer 
• Having a benign breast condition
• Having radiation therapy in the chest area
• Undergoing hormone therapy containing estrogen (such as for menopausal symptoms)
• Long-term alcohol consumption
• Long-term physical inactivity

However, there are differences between female and male breast cancer.

Specific risk factors that have been linked to female breast cancer include:

• Dense breast tissue
• An early first period (before age 12)
• Going through menopause after age 55
• A family history of ovarian cancer (in a first-degree relative)
• Being exposed to the drug DES (diethylstilbestrol, a synthetic estrogen)
• Higher bone density
• Not having children
• Not breastfeeding
• Giving birth for the first time at age 35 or older
• Naturally having high estrogen levels
• Taking combined oral contraceptives with estrogen and progestin (though this risk is reversible with discontinuation)

In general, male breast cancer is understudied compared to female breast cancer. But some factors that may raise the risk of male breast cancer include:

• Klinefelter syndrome, a rare condition of having XXY chromosomes (an extra X chromosome)
• Changes to testicles (like injury, inflammation, swelling, or surgical removal)
• Liver disease

Having any of these risk factors does not necessarily mean that you will get breast cancer. Talk to your healthcare provider about keeping up with routine screenings and what you can do to reduce your risk.

Diagnosis

Doctors may use different tests and procedures to diagnose breast cancer. As of May 2023, the U.S. Preventative Services Task Force (USPSTF) recommends that cisgender women and people assigned female at birth get mammograms every two years beginning at age 40.

Common diagnostics include:

• Standard physical exam: A healthcare provider will ask you about any recent health changes and your medical history.
• Blood tests: This helps evaluate how certain organs and tissues are functioning based on substances in your blood sample.
• Breast exam: A healthcare provider checks for lumps or other changes in your breasts.
• Mammogram: This is an X-ray of your breasts to check for potential signs of cancer. It’s the most common diagnostic tool used to check for breast cancer.
• Ultrasound: This visualizes tumors to help determine whether they are cancerous or benign.
• Magnetic resonance imaging (MRI): This is an imaging technique that can generate images of your organs and tissues. It is usually only done for women at high risk of breast cancer.
• Biopsy: This is a lab test where a sample of your breast tissue is removed and the cells are examined.

Once a diagnosis is confirmed, a healthcare provider will conduct additional tests and procedures to locate where the cancer has spread, determine the stage of the disease, and identify features of your particular cancer that may help guide treatment. These may include:

• Additional imaging tests
• Bone scan
• Lab testing to measure estrogen and progesterone receptors in cancerous tissue
• Lab testing to examine amount of HER2 gene and HER2 protein in cancerous tissue
• Multigene testing to identify gene mutations linked to a higher breast cancer risk (BRCA1, BRCA2, PALB2)

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Treatment

Breast cancer treatment differs by the type of cancer; its size, stage, and sensitivity to hormones; a person's age and health; and other factors. If you have breast cancer, you may receive one or more of the following therapies, depending on your condition:

Surgery: You might have breast-conserving surgery (such as lumpectomy), which removes cancerous breast tissue and some surrounding healthy tissue, but not the whole breast. Or, you might have a mastectomy—a surgery that removes the breast with cancer and, if necessary, the lymph nodes near the armpit.

Radiation therapy: This uses radiation to stop cancer growth at specific areas of the body. It can be used after a surgery or if the cancer has spread beyond the breast (metastasized). Options include external beam radiation therapy and brachytherapy.

Chemotherapy: Typically, this uses an intravenous (IV) therapy to deliver chemo drugs through your bloodstream to help stop cancer growth. It can be administered before or after surgery, or as the main treatment—usually for metastatic cancer.

Hormone therapy: If the cancer cells have estrogen or progesterone receptors, they can grow faster with those hormones present. Therefore, taking an anti-hormone drug can either lower the amount of estrogen or progesterone in your body or block them from cancer cells.

Targeted therapy: These drugs target features of cancer cells, which then blocks their growth. Trastuzumab is one that targets HER2-positive breast cancers.

Immunotherapy: This treatment helps your immune system attack cancer cells. You might take a substance that your body produces naturally (but needs more of) or a drug designed to aid your immune response. 

Talk to your healthcare provider about possible side effects of treatments. Besides these options, you could also participate in a clinical trial for new breast cancer treatment candidates—in which researchers are testing whether they work and how safe they are to use.

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Prevention

There's no sure way to prevent breast cancer. But there is a lot you can do to lower your risk:

• Maintain a healthy weight: This can reduce your risk of cancer and includes regular exercise, getting enough sleep, and limiting your daily stress. Also, eating a healthy diet, such as a Mediterranean diet that’s rich in fruits and vegetables and limits red and processed meat, may lower your risk.
• Exercise regularly: Being physically active can lower your risk of breast cancer. You'll want to aim for a minimum of 150 minutes of moderate activity (like brisk walking) or 75 minutes of vigorous exercise (like jogging) each week.
• Limit your alcohol intake: The American Cancer Society recommends limiting daily alcohol intake to 1 drink for women and 2 drinks for men, or avoiding alcohol entirely.
• Consider non-hormonal options to treat menopause symptoms: Using hormone therapy after menopause may increase your risk of developing breast cancer. Instead, your healthcare provider may recommend other treatments for menopausal hot flashes and stress.
• Consider breastfeeding: Choosing to breastfeed after giving birth can lower estrogen levels in your breasts, which may decrease your risk of breast cancer.
• Consider the risks of taking the pill: Taking combined oral contraceptives may raise the risk of female breast cancer, though research is limited. Talk with your healthcare provider about whether you should take the pill or try other birth control options.

Preventive Tests

Locating changes in the breasts and understanding your genetic risk for breast cancer can help you be vigilant about reducing your risk and help detect cancer early.

Genetic Testing

If you have a personal or family history of breast cancer, talk to your healthcare provider about whether you should get genetic testing. This involves a lab test on a DNA sample—such as from your saliva or blood. It can check whether you have any specific gene mutations that have been linked to an increased risk for breast cancer.

BRCA gene mutations are known to be more common in certain people. If you are of Ashkenazi Jewish, West African, Dutch, Belgian, Icelandic, or Swiss ancestry—especially if you also have a family history of breast cancer—you may be more likely to have one or more BRCA gene mutations.

Breast Cancer Screenings

The thought of getting a screening often starts with a question of when. It’ll depend on your individual risk for breast cancer.

Some risk factors carry more weight than others. Factors such as genetic, hereditary, or personal medical history of breast cancer, or a history of chest radiation (before age 30) indicate that you have a higher risk of developing breast cancer.

If you are at higher risk for breast cancer, experts recommend starting routine screenings at an earlier age. This might begin around age 35 for men or age 30 for women.

Breast Exams

Regular breast exams can help you understand what’s normal for your breasts and what isn’t. Your healthcare provider may conduct a clinical breast exam during your annual physical. They can teach you how to do this exam on your own time (known as a breast self-exam). You can also refer to tutorials from official medical associations.

Though there hasn’t been enough research to suggest that a breast exam can change your risk for breast cancer, it’s an extra precaution you can take for early detection, especially if you’re at high risk for breast cancer. However, it’s not recommended to rely on breast exams alone for cancer detection. Even if you do breast exams, experts recommend continuing with standard screening methods, like mammograms.

Other Options for People Who Are High Risk

If you are at higher risk for female breast cancer, such as having a BRCA gene mutation, there are additional preventive measures you can take—even when you don’t have cancer.

You could ask your healthcare provider about taking antiestrogens, which prevent cells from making or using estrogen. Another option is having preventive surgery to help lower your risk. This could be a surgery to remove your breast tissue (bilateral risk-reducing mastectomy) or to remove your ovaries and fallopian tubes (prophylactic salpingo-oophorectomy).

A Quick Review

Breast cancer is cancer that originates in breast tissue. There are several types of breast cancer that vary by severity and spread, though common symptoms include an abnormal growth on the breast or other breast changes, like nipple inversion. A healthcare provider can provide a diagnosis and determine the type, stage, and status of breast cancer. Several treatment options are available, such as radiation therapy, surgery, chemotherapy, and more. 

Some people may have a higher risk, such as those with a genetic predisposition or family history of breast cancer. Early screening and preventive tests are available to help determine your risk for breast cancer, as well as procedures to prevent local breast cancer from spreading—particularly if you have a high genetic risk.