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What Is Breast Cancer?

Breast cancer is a disease that arises when cells in one or both breasts grow uncontrollably.1 Since these cells divide faster than they should, they can form tumors.2 In its earliest stages, breast cancer forms inside lobules or ducts that contain milk.3 However, breast cancer can spread to other parts of the body if cancer cells travel through blood and lymph vessels; this is known as metastasis.1

Breast cancer can begin in any of the three main parts of the breast:1

  • The lobules (glands that produce milk)
  • The ducts (tubes that transport milk to the nipple)
  • The connective tissue surrounding them

While there are several types of breast cancers, the most common are invasive ductal carcinoma and invasive lobular carcinoma.1 About 70–80 percent of invasive breast cancers start in the cells of the ducts (invasive ductal carcinoma), while 10–15 percent begin in the cells of the lobules (invasive lobular carcinoma).1

At stage 0, the earliest stage of breast cancer, the disease is contained within the lobule or duct where it first started.4 Breast cancer may then invade nearby breast tissue, lymph nodes, and other organs. The spread of the disease to distant organs, called metastasis, can make breast cancer fatal.3

When breast cancer is diagnosed early, treatment options like surgery, radiation, chemotherapy, and hormonal therapy can help reduce the risk of death.3

 

Prevalence of Breast Cancer

Breast cancer is the second most common cancer among people assigned female at birth in the United States. Each year, it’s responsible for nearly 30 percent of all cancers among this demographic.6

The American Cancer Society estimates there will be about 59,080 new cases of early-stage breast cancer (ductal carcinoma in situ), and around 316,950 new cases of invasive breast cancer in 2025 among those assigned female at birth. The disease tends to be more prevalent among people who are middle-aged and older. The median age of diagnosis is 62.6

Tragically, breast cancer is a leading cause of cancer death among people assigned female at birth. In 2025, the American Cancer Society expects about 42,170 deaths from the disease.6

Overall, the incidence of breast cancers has grown by 1 percent per year in recent years. However, the overall death rate has declined by 44 percent between 1989 and 2022. Experts attribute this change to early detection, awareness campaigns, and treatment improvements. Now, there are more than 4 million breast cancer survivors in the United States.6

Causes and Risk Factors

What Causes Breast Cancer
What Causes Breast Cancer?

Scientists still do not fully understand the causes of breast cancer. Research suggests that certain risk factors increase the likelihood of developing breast cancer. And while gene mutations can cause healthy breast cells to become cancerous, many of those genetic changes have not yet been identified by researchers.7

 

Breast Cancer and Genetics

Genes influence how cells work. The proto-oncogenes contained in normal cells help control cellular growth, and genes called tumor-suppressor genes determine how often cells divide. If proto-oncogenes or tumor suppressor genes mutate, cells can start growing out of control and become cancerous.7

Some genetic mutations are inherited in the DNA that parents pass on to their children, including gene changes known to increase the risk of developing certain kinds of cancer. Notably, mutations in the BRCA tumor-suppressor genes can be inherited. Yet only around 10% of breast cancer diagnoses are linked to known inherited gene abnormalities.7

Other cases may develop from unknown hereditary mutations. Researchers believe that about 90% of breast cancers arise from unidentified acquired gene changes that happen after birth. These changes may stem from factors like radiation, exposure to cancer-causing chemicals, or random cellular changes.7

Breast Cancer Risk Factors

Certain hormonal, environmental, and lifestyle factors may increase the risk for breast cancer, including:8

  • People who experience their first pregnancy after age 30, do not breastfeed, or never complete a full-term pregnancy may face greater risk. People who begin menstruating before age 12 or start menopause after age 55 are exposed to hormones for longer, which increases their risk for breast cancer.

  • People with dense breasts are at greater risk for breast cancer. Dense breasts can also make it more difficult to spot potentially cancerous changes on a mammogram.

  • A person who has had breast cancer once is more likely to get it again. Some noncancerous diseases of the breast are associated with a higher risk of breast cancer.

  • A person is at greater risk if an immediate relative (parent, sibling, or child) or multiple relatives on one side of the family have had breast cancer. A family history of ovarian cancer may also increase the risk for breast cancer.

  • Undergoing radiation therapy to the chest or breasts (for example, to treat another cancer) before age 30 raises the risk of developing breast cancer.

  • Patients who took DES, a drug given during pregnancy between 1940 and 1971 to prevent miscarriage, have a higher breast cancer risk. People whose mothers took it while pregnant with them may have a higher breast cancer risk.

  • Being physically inactive throughout life and being overweight after menopause can increase risk.

  • Taking a hormone replacement therapy that includes both estrogen and progesterone for more than five years during menopause can increase the risk of breast cancer. Studies also suggest links between breast cancer and certain birth control pills. In some cases, hormonal changes caused by working night shifts may influence the development of breast cancer.

  • Increased alcohol consumption raises the risk of breast cancer. Smoking is also linked to a higher risk.

Male Breast Cancer

Breast cancer in people assigned male at birth can also occur, but it’s much less common compared to breast cancers in those assigned female at birth.3 Before puberty, all children have a small amount of breast tissue, including several ducts under the nipples and areola.9 When a person assigned female at birth starts puberty, estrogen causes ducts to grow and lobules to form.10,11

Even following puberty, people assigned male at birth typically have much lower levels of hormones such as estrogen. As a result, breast tissue usually doesn't grow much. However, people assigned male at birth still have breast ducts—albeit few, if any, lobules.9

 

How Common Is Male Breast Cancer?

Roughly <1 percent of all breast cancers occur in people assigned male at birth.3 In 2025, experts anticipate 2,800 new diagnoses of invasive breast cancer and 510 deaths from the disease among this population in the U.S.11

Male Breast Cancer Causes and Risk Factors

Researchers don't fully understand what causes male breast cancer, but several known risk factors include:13

  • Aging increases the risk of developing male breast cancer—the average age at diagnosis is 72 years old.

  • About 20 percent of patients with male breast cancer have a close family member with the disease. Inherited gene mutations, such as mutations in the BRCA gene, may also increase the risk.

  • Roughly 1 in 1,000 people assigned male at birth have cells with one or more extra X chromosomes. Instead of the more common XY pair, their cells may have an XXY combination. This condition, known as Klinefelter syndrome, often causes infertility, higher levels of estrogen compared to other people assigned male at birth, and a 20-60 times greater chance of developing breast cancer.

  • Having one's chest repeatedly exposed to radiation increases the risk of developing breast cancer.

  • Heavy drinking increases the risk of liver disease. Because the liver helps regulate sex hormones, severe liver diseases such as cirrhosis can lead to higher levels of estrogen and lower levels of androgens (male sex hormones), thereby increasing breast cancer risk.

  • Because high levels of estrogen may increase breast cancer risk, male patients who receive hormone therapy for prostate cancer with estrogen-related drugs may be more likely to develop breast cancer.

  • Fat cells convert androgens, or male sex hormones, into estrogens which can increase breast cancer risk.

  • Having undescended testicles, having mumps as an adult, or having testicles surgically removed may increase the risk of developing breast cancer.

Currently, male breast cancer treatment is similar to other breast cancer treatments. Researchers continue to investigate whether different therapies would lead to better outcomes.13

Breast Cancer Types

Most breast cancers begin in the cells lining the milk ducts or lobules: these are known as adenocarcinomas.15 There are other types of cancer that can be found in the breast, but they are rare.16 This includes:

  • Sarcomas, which begin in connective breast tissue cells and account for less than 1 percent of all breast cancers.16
  • Angiosarcomas, which begin in cells lining blood or lymph vessels and may involve breast tissue or skin.16
  • Paget’s disease of the breast, which starts in the breast ducts and spreads to the skin of the nipple, accounting for 1 to 3 percent of all breast cancers.16
  • Phyllodes tumor of the breast, which is a growth in the connective tissue of the breast that is usually noncancerous but can be cancerous in some cases.15

  • To help determine appropriate treatment options, oncologists test cancer cells removed during a biopsy or surgery to determine whether they have receptors for the hormones estrogen and progesterone. Receptors are specific proteins in or on cells where substances in the blood, such as hormones, bind to the cell. Healthy breast cells have receptors where the hormones estrogen and progesterone attach.17

    However, breast cancer cells can also have these receptors. About 75 percent of breast cancers have at least one type of hormone receptor. Knowing whether these receptors are present is important because they influence how cancer cells grow. Understanding this growth helps doctors select appropriate treatment options.17

    Based on the presence or absence of these receptors, breast cancer is classified as hormone-receptor positive (HR+) or hormone-receptor negative (HR-). Breast cancers that are HR+ have receptors for estrogen, progesterone, or both hormones.17 Around 75 to 80 percent of invasive breast cancers are HR+.17,18 Breast cancers that are HR- do not have receptors for either estrogen or progesterone.17

    For people diagnosed with HR+ breast cancer, blocking estrogen and progesterone from reaching cellular receptors may help slow down cancer growth and stop it from spreading. Oncologists often treat HR+ cancers with hormone therapy, which reduces hormone levels or blocks hormone receptors. Unfortunately, this treatment option isn’t appropriate for patients with HR- disease.17

  • HER2 is a protein that helps breast cancer develop faster. If breast cancer cells have higher than normal levels of HER2, they are classified as HER2-positive (HER2+). If levels are lower than normal, the breast cancer is classified as HER2-negative (HER2-).17

    Breast cancers with higher amounts of the HER2 protein occur in about 15 to 20 percent of cases. These cancers have a better chance of responding to HER2-targeted drugs. Just as with knowing a tumor’s hormone receptor status, knowing its HER2 status helps oncologists select the best treatment options.19,20

  • This type of breast cancer is HER2- and lacks hormone receptors for estrogen and progesterone. Since these cancer cells don’t have hormone receptors, hormone therapy is not a treatment option. Additionally, since these cancer cells do not have high levels of HER2, medications affecting the HER2 protein also aren’t appropriate.17

    If triple-negative breast cancer hasn’t spread to other tissues, surgery may be an effective treatment option. Chemotherapy, radiation therapy, immunotherapy, or targeted therapy using antibody-drug conjugates (ADJs) may also work.22

  • This type of breast cancer grows due to higher-than-normal levels of estrogen, progesterone, and the HER2 protein. Triple-positive breast cancer accounts for about 10 percent of cases. Generally, doctors recommend chemotherapy, hormone therapy, or targeted therapy—or a combination of the three—to treat this form of breast cancer.21

  • Breast cancer is called "in situ" when it’s contained within the area where it first began to form.24 Ductal carcinoma in situ (DCIS) is confined in the breast ducts and is considered an early form of cancer.25 Lobular carcinoma in situ is contained in the lobules and is not considered to be cancer, although it can increase the risk of invasive cancer in the future.24

    Breast cancer is described as "invasive" when it spreads into the surrounding breast tissue. The most common types are invasive ductal carcinoma, which accounts for around 80 percent of invasive breast cancers, and invasive lobular carcinoma, which accounts for about 10 percent of invasive breast cancer cases.25

Breast Cancer Stages

In addition to identifying the type of breast cancer a patient has, doctors classify the cancer's stage. This helps to determine treatment and the likelihood of survival.26

When staging breast cancer, doctors consider several factors to help determine how early or advanced the cancer is, including:26

  • The size of the tumor
  • Whether or not lymph nodes have cancer cells in them and how many lymph nodes are involved
  • Whether it has involved the tissue of the chest wall outside of the breast
  • Whether the cancer has spread (metastasized) to organs distant from the breast
  • ER, PR, and HER2 status
  • Grade of the cancer cells, which compares how they look to normal, healthy cells

Breast cancers are classified from stage 0 (early stage, also called carcinoma in situ) through stage 4 (advanced). Generally, the lower the number of the stage, the less the cancer has spread. Higher numbers, like stage 4, indicate that cancer has spread more.26

Doctors usually use the TNM system to stage breast cancer:26

  • T describes how large the main tumor is and whether it’s spread to areas of the skin or chest wall. T scores range from 0 to 4. Higher T numbers mean that the tumor is bigger or that it has spread farther.
  • N specifies if the cancer has spread to nearby lymph nodes and how many lymph nodes near the breast contain cancerous cells. Scores range from 0 to 3, with 0 indicating no spread and 3 indicating that the cancer has spread to many lymph nodes including larger tumors or lymph nodes further from the breast.
  • M indicates whether breast cancer has spread to other organs or tissues, like the bones, lungs, or brain. M scores are either 0 or 1, with 0 meaning cancer hasn’t spread. A M score of 1 means the cancer has spread to distant parts of the body.

 

Metastatic Breast Cancer

In 2020, approximately 168,000 individuals assigned female at birth were living with metastatic breast cancer in the U.S.27 Otherwise known as stage 4 breast cancer, metastatic cancer is cancer that has reached other parts of the body, such as the liver, brain, lungs, or bones.28

As many as 30 percent of people diagnosed with early-stage breast cancer go on to develop metastatic breast cancer. Metastatic disease can arise as “distant recurrence” months or years after initial diagnosis at an earlier stage.28

An initial diagnosis of metastatic breast cancer is called de novo metastatic breast cancer—up to 10 percent of breast cancers have already metastasized when doctors make a first diagnosis. This means that the cancer has already reached other parts of the body by the time it is first detected.28

Metastatic breast cancer is incurable and, unfortunately, life expectancy following a diagnosis is typically limited.28,29 But some treatments may prolong life, alleviate symptoms, reduce tumor size, or slow tumor growth.30 Patients will often continue a specific treatment if it controls the cancer and if side effects are manageable. If the treatment stops working or the patient can no longer tolerate specific treatments, patients may try other treatment options.28

Depending on the disease subtype, the five-year survival rate for people diagnosed with metastatic breast cancer ranges between 14 to 46 percent.31 Other factors, such as hormone receptor status, also affect survival rates.32

Breast Cancer Symptoms

Breast Cancer Symptoms

While experts highlight the benefits of regular breast cancer screening, they also caution that mammograms don't always find every instance of breast cancer. It's important to know how your breasts normally look and feel so you can spot early signs of breast cancer.33

A new lump or mass is the most common symptom that most people detect. Cancerous masses are typically painless and hard with irregular edges, but they can also be tender (or even painful) with soft or rounded edges. Any new lump should be checked by an experienced health care provider.33

Other breast cancer symptoms might include:33

  • Swelling of the breast
  • Swollen lymph nodes under the arm or around the collar bone
  • Skin dimpling on the breast (sometimes resembling an orange peel)
  • Pain in the breast or nipple
  • Nipple retraction (inverting inward)
  • Red, dry, flaky, or thickened skin on the nipple or breast
  • Nipple discharge other than breast milk

Many of these symptoms result from other medical conditions, but they should be reported to healthcare professionals for examination.33

Diagnosis and Treatment

After diagnosing a person with breast cancer, doctors will explain treatment options and create treatment plans specific to the type of cancer and goals of treatment.33 Some breast cancer treatments can be highly effective—5-year survival rates are over 99 percent for people who are diagnosed with early-stage breast cancer. Survival rates for breast cancers diagnosed at later stages are lower.29

Breast Cancer Treatment

Patients with breast cancer have different treatment options that depend on several factors, such as which, if any, hormones are involved and whether breast cancer is detected early or only after it has reached metastatic stage.35

  • People diagnosed with ductal carcinoma in situ (DCIS), or stage 0 breast cancer, generally are treated with surgery:36

    • Breast conserving surgery: A surgeon removes both the tumor (lumpectomy) and a small portion of breast tissue surrounding it, retaining most of the breast tissue.
    • Mastectomy: Surgeons remove the entire breast (simple mastectomy).

    Breast conserving surgery is usually followed by radiation to reduce the risk of recurrence. If DCIS is hormone receptor-positive, hormone therapy for a period of five years after surgery may help avoid recurrent DCIS or an invasive form of breast cancer.36

  • A diagnosis of stage I to III breast cancer generally requires a more complex treatment approach. Treatment may include surgery, radiation, and/or systemic therapies.37

    There are several surgical options for people with stage I-III breast cancer, including:37,38

    • Lumpectomy: The lumpectomy and other breast-sparing surgeries involve removing cancerous tissue, and some normal surrounding tissue, while leaving the rest of the breast intact. Surgeons may remove some lymph nodes for additional study. Lumpectomy may also be referred to as breast-conserving surgery, partial mastectomy, or segmental mastectomy.
    • Mastectomy: Mastectomy involves surgically removing all of the breast. There are different kinds of mastectomies that involve different amounts of tissue and lymph nodes.
    • Mastectomy with reconstruction: This procedure combines a mastectomy with surgical reconstruction of the breast. Typically, a plastic surgeon performs the breast reconstruction procedure using implants or tissue taken from other parts of the body to reconstruct what was removed. Some people choose to have breast reconstruction surgery performed at the same time as surgery to remove the tumor. However, patients who will need radiation therapy should wait until radiation is complete before having breast reconstruction.

    In many cases, patients also receive neoadjuvant therapy: these therapies are systemic, meaning they reach cells throughout the body by traveling through the bloodstream. Neoadjuvant systemic therapies are most often chemotherapy, but other treatments, like hormone therapy, may also help.37 Radiation therapy may also be administered as neoadjuvant treatment.39

    Other therapies, such as HER2-targeted drugs, hormone therapy, and immunotherapy, may be beneficial to patients with stage I-III breast cancer.37

  • Treating late-stage (metastatic) breast cancer often focuses on preventing further cancer growth and preventing symptoms and complications of the disease. In a small number of cases, surgery or radiation therapy may help, but systemic treatments, such as chemotherapy, hormone therapy, immunotherapy, or targeted drug therapy are mainstays of treatment.39

    To better determine treatment options, doctors may recommend biomarker testing. Biomarkers are genetic mutations, proteins, hormones, genes, or other molecules that signal the presence of breast cancer.41

    While testing for three specific biomarkers—estrogen receptor status, progesterone receptor status, and HER2 status—is common for all breast cancer tumors, your doctor may also want to check for the presence of other biomarkers on tumor cells. Your doctor may recommend testing for:41

    • PD-L1 status: If breast cancer is PD-L1-positive, some immunotherapy medications, such as pembrolizumab (Keytruda), may help.
    • ESR1 mutations: The ESR1 gene directs the body to make estrogen receptors. Metastatic breast cancers often develop ESR1 mutations during treatment with hormone therapy, making that type of treatment less effective.
    • AKT1 and PTEN mutations: Both the AKT1 gene and the PTEN gene help determine how fast cells in the body grow and divide. If mutations occur in one or both genes, cells can grow out of control. Additional treatment options may be available for people with metastatic, HR+, HER2- breast cancer with either of these mutations that continues to grow after hormone therapy.
    • PIK3CA mutations: In healthy individuals, the PIK3CA gene causes the body to make the PI3K protein. That protein, in turn, helps cells get the energy they need to survive. PIK3CA mutations affect how the PI3K protein works, which may allow cancer cells to survive and multiply. Additional treatment options may be available for people with metastatic, HR+, HER2- breast cancer with this mutation that continues to grow after hormone therapy.
    • BRCA1 and BRCA2 mutations: Mutations of the BRCA1 and BRCA2 genes are the most common causes of hereditary, or inherited, breast cancers. Normally, these genes help make proteins that repair damaged cellular DNA. When mutated, these genes promote abnormal cellular growth which may result in cancer.42

  • Chemotherapy helps eliminate cancer cells throughout the body and helps prevent cancer from forming in other body areas42. Chemotherapy may include the following drugs and drug types:44

    • Anthracyclines
    • Taxanes
    • 5-fluorouracil
    • Cyclophosphamide
    • Carboplatin

    Additional chemotherapy agents may be used for metastatic breast cancer.44

  • People with hormone receptor positive breast cancers, including both ER+ and PR+, may be candidates for hormone therapy, also known as endocrine therapy.45

    This treatment uses hormones to prevent breast cancer from returning. It may also be used to treat recurrent or metastatic cancers. Typically, patients will take hormone therapy for about 5 years, but treatment may last longer if the cancer has a higher chance of recurrence. Although they all work on estrogen or progesterone receptors, hormone therapy medications belong to different classes, such as:45

    • Aromatase inhibitors (AIs)
    • Selective estrogen receptor modulators (SERMs)
    • Selective estrogen receptor degraders (SERDs)

  • In immunotherapy, certain medications help the patient’s immune system better identify and eliminate cancer cells. These medicines target specific proteins in the immune system that boost its ability to fight cancer. Although many people with breast cancer benefit from immunotherapy, this type of treatment isn’t appropriate for all types of breast cancers.46

    PD-1 inhibitors, part of a class of immunotherapy agents called immune checkpoint inhibitors, are a common type of immunotherapy medication. The immune system features proteins called “checkpoints,” which stop the immune system from destroying healthy cells. Breast cancer cells are sometimes able to use these checkpoint proteins to their advantage, escaping detection by the immune system. Immune checkpoint inhibitors, like PD-1 inhibitors, override the PD-1 protein checkpoint, generating an immune response that may reduce the size of tumors.46

  • Doctors may suggest other treatments, like radiation therapy, to help treat or prevent cancer recurrence, symptoms, or complications. This treatment option uses high-energy rays or particles that target and eliminate breast cancer cells. There are two primary types of radiation for breast cancer treatment:47

    • External beam radiation therapy (EBRT): EBRT is the most frequently used radiation therapy for breast cancer. With EBRT, a machine focuses and delivers the radiation to the site of breast cancer. If the cancer reached other areas, such as lymph nodes, radiation oncologists may target these places as well.
    • Brachytherapy: Whereas EBRT is an outside-in approach to radiation therapy, brachytherapy is an inside-out approach. A device containing radioactive seeds or pellets is placed into breast tissue at the site of the removed tumor for a short time.

  • Targeted therapies are named for their ability to target breast cancer cell proteins that impact how the cells grow and spread. These therapies work to stop or slow the growth of cancer cells  They may be administered via injection, intravenously (IV), or as pills. There are targeted therapies for HER2-positive breast cancer, hormone receptor-positive breast cancer, for breast cancer featuring the BRCA gene mutation, and for triple-negative breast cancer.48

    Targeted therapy for HER2-positive breast cancer

    Monoclonal antibodies are often used in cases of HER2-positive breast cancer, which comprise about 15 to 20 percent of all breast cancer cases. Monoclonal antibodies are human-made immune system proteins, called antibodies. They bind with the HER2 protein on cancer cells, which can slow or stop g their growth.48

    Antibody-drug conjugates (ADJs) are combination drugs that feature a monoclonal antibody and a chemotherapy medication. The monoclonal antibody attaches to the HER2 protein on the cancer cell, bringing the chemotherapy right to the site of the cancer.48

    Kinases, such as HER2, are proteins that play a critical role in relaying growth signals to cells. Kinase inhibitors work to block these proteins to stop prevent cell growth messaging from happening.48

    Targeted therapy for hormone receptor-negative breast cancer

    These drugs work in conjunction with hormone therapy:48

    • CDK4/6 inhibitors: These drugs block specific kinases in hormone-receptor positive breast cancer cells. Blocking these proteins limits the cells’ ability to divide and may slow the growth of cancer.
    • mTOR inhibitor: This type of targeted therapy blocks a specific protein, called mTOR, in hormone receptor-positive breast cancer. This can limit the cancer cells’ ability to grow or divide, and it may even stop tumors from creating new blood vessels, thwarting their growth.
    • PI3K inhibitor: This targeted therapy works to block a type of the PI3K protein. Once this protein is blocked, it may stop the cancer cell from growing.
    • AKT inhibitors: This type of medication works to block the AKT protein, which is important for cellular signaling. In many cases, doctors prescribe AKT inhibitors along with other medications to treat advanced hormone receptor-positive breast cancers.
    • Antibody-drug conjugates: This type of therapy features a monoclonal antibody combined with a chemotherapy medication. The monoclonal antibody directly targets certain proteins on the surface of breast cancer cells, bringing chemotherapy directly to them.

    Targeted therapy for BRCA gene mutations

    BRCA1 and BRCA2 are two genes often responsible for breast cancer that is inherited, also known as hereditary breast cancer. When these genes are normal, they create proteins that repair damaged DNA. But when these genes mutate, they may cause cells to grow abnormally, which may lead to breast cancer.42

    Targeted therapies for breast cancers with BRCA gene mutations involve a class of drugs known as PARP inhibitors. Normally, the PARP protein helps cells repair damaged DNA within the cell, similarly to normal BRCA gene function.48

    Mutated BRCA genes struggle to repair damaged DNA. By adding a PARP inhibitor, the DNA repair process may stop completely in the cancer cells, causing them to die and slowing or stopping the spread of breast cancer.48

    Targeted therapy for triple-negative breast cancer

    In cases of triple-negative breast cancer, the cancer cells lack estrogen or progesterone receptors and do not produce the HER2 protein (or produce very little of it). People with this type of breast cancer may receive an antibody-drug conjugate as a form of targeted therapy. For example, the monoclonal antibody targets and binds with the Trop-2 protein on breast cancer cells. Some cancer cells may have high levels of Trop-2, which can lead to accelerated cancer growth. After the monoclonal antibody binds to the Trop-2 protein, a chemotherapy medication delivers treatment directly to the cell.48

Global Impact of Breast Cancer

Global Impact of Breast Cancer

In 2022, 2.3 million people worldwide were diagnosed with breast cancer, and 670,000  lost their lives to the disease.3

Not only is the disease a burden on breast cancer patients and their families, but there's also a high global economic cost for cancer in general—including healthcare spending and productivity losses.49

Frequently  Asked Questions About Breast Cancer

  • Being familiar with the normal look and feel of your breasts is a component of breast health.33 Also, mammograms to screen for cancer can support early detection.50

  • Breast cancer lumps are typically painless and hard with irregular edges. However, some patients may experience tender or even painful lumps with soft or rounded edges. That's why it's important to have any new lump checked by an experienced healthcare provider.33

  • Breast cancer starts when cells in one or both breasts grow uncontrollably. Since these cells divide faster than they should, they accumulate into a mass. Tumors can grow in the breast's lobules (milk-producing glands), ducts (canals that transport milk to the nipple), or the connective tissue surrounding them.1,3

  • Yes, male breast cancer accounts for approximately 0.5–1 percent of all breast cancers.3 People assigned male at birth still have a small amount of breast tissue including ducts, and potentially some lobules. Those ducts and lobules are susceptible to breast cancer.9

  • Regular mammograms are a good way for people with average breast cancer risk to check for signs of cancer. During a mammogram, low energy X-rays provide pictures of internal breast tissue, allowing doctors to better identify any areas of change.50

  • After receiving a breast cancer diagnosis, your care team will work quickly to stage the cancer and determine which treatment options may work best for you.26 Your doctor may also connect you to resources to help you make decisions about your care.

  • Most cancers of the breast are carcinomas (cancers that originate in cells lining the breast) that start in the milk ducts or lobules. Breast carcinomas start out in situ, meaning they are contained in the duct or lobule. Without treatment, they can become invasive carcinomas that spread into the surrounding breast tissue and then to lymph nodes and other parts of the body.15

    A less common type of breast cancer, angiosarcoma, begins in cells that line blood vessels or lymph vessels and can involve breast tissue or skin. Overall, sarcomas including angiosarcoma account for less than 1 percent of all breast cancers. Phyllodes tumors begin in the connective tissue of the breast and are often benign but can become cancerous.15

Learn More About Breast Cancer

The information contained on this page is provided for your general information only. It is not intended as a substitute for seeking medical advice from a healthcare provider. Pfizer is not in the business of providing medical advice and does not engage in the practice of medicine. Pfizer under no circumstances recommends particular treatments for specific individuals and in all cases recommends consulting a physician or healthcare center before pursuing any course of treatment.

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