The breast is made up of lobes and ducts. Each breast has 15-20 sections called lobes. Each lobe has many smaller sections called lobules. Lobules end in dozens of tiny bulbs that can make milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts.
Each breast also has blood vessels and lymph vessels. The lymph vessels carry an almost colorless fluid called lymph. Lymph vessels carry lymph between lymph nodes. Lymph nodes are small bean-shaped structures that are found throughout the body. They filter substances in lymph and help fight infection and disease. Clusters of lymph nodes are found near the breast in the axilla (under the arm), above the collarbone, and in the chest.
What Is Breast Cancer?
Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast.
The most common type of breast cancer is ductal carcinoma, which begins in the cells of the ducts. Cancer that begins in the lobes or lobules is called lobular carcinoma and is more often found in both breasts than are other types of breast cancer. Inflammatory breast cancer is an uncommon type of breast cancer in which the breast is warm, red, and swollen.
What Are the Risk Factors for Breast Cancer in Women?
Anything that increases your chance of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. Talk to your doctor if you think you may be at risk for breast cancer.
A family history of breast cancer and other factors increase the risk of breast cancer. Risk factors for breast cancer include the following:
- A personal history of invasive breast cancer, ductal carcinoma in situ (DCIS), or lobular carcinoma in situ (LCIS)
- A personal history of benign (noncancer) breast disease
- A family history of breast cancer in a first-degree relative (mother, daughter, or sister)
- Inherited changes in the BRCA1 or BRCA2 genes or in other genes that increase the risk of breast cancer
- Breast tissue that is dense on a mammogram
- Exposure of breast tissue to estrogen made by the body. This may be caused by:
- Menstruating at an early age
- Older age at first birth or never having given birth
- Starting menopause at a later age
- Taking hormones such as estrogen combined with progestin for symptoms of menopause
- Treatment with radiation therapy to the breast/chest
- Drinking alcohol
Older age is the main risk factor for most cancers. The chance of getting cancer increases as you get older.
Is Breast Cancer Caused Due to Inherited Gene Mutations?
The genes in cells carry the hereditary information that is received from a person's parents. Hereditary breast cancer makes up about 5-10 percent of all breast cancer. Some mutated genes related to breast cancer are more common in certain ethnic groups.
Women who have certain gene mutations, such as a BRCA1 or BRCA2 mutation, have an increased risk of breast cancer. These women also have an increased risk of ovarian cancer, and may have an increased risk of other cancers. There are tests that can detect (find) mutated genes. These genetic tests are sometimes done for members of families with a high risk of cancer.
What Are the Protective Factors for Breast Cancer?
Anything that decreases your chance of getting a disease is called a protective factor. The use of certain medicines and other factors decrease the risk of breast cancer.
Protective factors for breast cancer include the following:
- Taking any of the following:
- Estrogen-only hormone therapy after a hysterectomy
- Selective estrogen receptor modulators (SERMs)
- Aromatase inhibitors (AIs)
- Less exposure of breast tissue to estrogen made by the body. This can be a result of:
- Early pregnancy
- Getting enough exercise
- Having any of the following procedures:
- Mastectomy to reduce the risk of cancer
- Oophorectomy to reduce the risk of cancer
- Ovarian ablation
What Are the Signs and Symptoms of Breast Cancer?
Signs of breast cancer include a lump or change in the breast.
These and other signs may be caused by breast cancer or by other conditions. Check with your doctor if you have any of the following:
- A lump or thickening in or near the breast or in the underarm area
- A change in the size or shape of the breast
- A dimple or puckering in the skin of the breast
- A nipple turned inward into the breast
- Fluid, other than breast milk, from the nipple, especially if it's bloody
- Scaly, red, or swollen skin on the breast, nipple, or areola (the dark area of skin around the nipple)
- Dimples in the breast that look like the skin of an orange, called peau d'orange
How Is Breast Cancer Diagnosed?
Tests that examine the breasts are used to detect (find) and diagnose breast cancer.
Check with your doctor if you notice any changes in your breasts. The following tests and procedures may be used:
- Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
- Clinical breast exam (CBE): An exam of the breast by a doctor or other health professional. The doctor will carefully feel the breasts and under the arms for lumps or anything else that seems unusual.
- Mammogram: An X-ray of the breast.
- Ultrasound exam: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. The picture can be printed to be looked at later.
- Magnetic resonance imaging (MRI): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of both breasts. This procedure is also called nuclear magnetic resonance imaging (NMRI).
- Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease.
- Biopsy: The removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for signs of cancer. If a lump in the breast is found, a biopsy may be done.
There are four types of biopsy used to check for breast cancer:
- Excisional biopsy: The removal of an entire lump of tissue.
- Incisional biopsy: The removal of part of a lump or a sample of tissue.
- Core biopsy: The removal of tissue using a wide needle.
- Fine-needle aspiration (FNA) biopsy: The removal of tissue or fluid, using a thin needle.
If cancer is found, tests are done to study the cancer cells.
Decisions about the best treatment are based on the results of these tests. The tests give information about:
- How quickly the cancer may grow
- How likely it is that the cancer will spread through the body
- How well certain treatments might work
- How likely the cancer is to recur (come back)
Tests include the following:
- Estrogen receptor (ER) and progesterone receptor (PR) test: A test to measure the amount of estrogen and progesterone (hormones) receptors in cancer tissue. If there are more estrogen and progesterone receptors than normal, the cancer is called estrogen and/or progesterone receptor positive. This type of breast cancer may grow more quickly. The test results show whether treatment to block estrogen and progesterone may stop the cancer from growing.
- Human epidermal growth factor type 2 receptor (HER2/neu) test: A laboratory test to measure how many HER2/neu genes there are and how much HER2/neu protein is made in a sample of tissue. If there are more HER2/neu genes or higher levels of HER2/neu protein than normal, the cancer is called HER2/neu positive. This type of breast cancer may grow more quickly and is more likely to spread to other parts of the body. The cancer may be treated with drugs that target the HER2/neu protein, such as trastuzumab and pertuzumab.
- Multigene tests: Tests in which samples of tissue are studied to look at the activity of many genes at the same time. These tests may help predict whether cancer will spread to other parts of the body or recur (come back).
There are many types of multigene tests. The following multigene tests have been studied in clinical trials:
- Oncotype DX: This test helps predict whether stage I or stage II breast cancer that is estrogen receptor positive and node negative will spread to other parts of the body. If the risk that the cancer will spread is high, chemotherapy may be given to lower the risk.
- MammaPrint: This test helps predict whether stage I or stage II breast cancer that is node-negative will spread to other parts of the body. If the risk that the cancer will spread is high, chemotherapy may be given to lower the risk.
Based on these tests, breast cancer is described as one of the following types:
- Hormone receptor positive (estrogen receptor positive (ER+) and progesterone receptor positive (PR+)) or hormone receptor negative (estrogen receptor negative (ER-) and progesterone receptor negative (PR-)).
- HER2/neu positive or HER2/neu negative.
- Triple negative (estrogen receptor, progesterone receptor, and HER2/neu negative).
This information helps the doctor decide which treatments will work best for your cancer.
How Is Staging Done for Breast Cancer?
The process used to find out whether the cancer has spread within the breast or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. The results of some of the tests used to diagnose breast cancer are also used to stage the disease.
After breast cancer has been diagnosed, tests are done to find out if cancer cells have spread within the breast or to other parts of the body. The following tests and procedures also may be used in the staging process:
- Sentinel lymph node biopsy (SLNB): The removal of the sentinel lymph node during surgery. The sentinel lymph node is the first lymph node to receive lymphatic drainage from a tumor. It is the first lymph node the cancer is likely to spread to from the tumor. A radioactive substance and/or blue dye is injected near the tumor. The substance or dye flows through the lymph ducts to the lymph nodes. The first lymph node to receive the substance or dye is removed. A pathologist views the tissue under a microscope to look for cancer cells. If cancer cells are not found, it may not be necessary to remove more lymph nodes.
- Chest X-ray: An X-ray of the organs and bones inside the chest. An X-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
- Computed tomography (CT)/computerized axial tomography (CAT) scan: A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an X-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly.
- Bone scan: A procedure to check if there are rapidly dividing cells, such as cancer cells, in the bone. A very small amount of radioactive material is injected into a vein and travels through the bloodstream. The radioactive material collects in the bones with cancer and is detected by a scanner.
- Positron emission tomography (PET) scan: A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
Stages of Breast Cancer
The following stages are used for breast cancer:
The breast cancer stage is based on the results of tests that are done on the tumor and lymph nodes removed during surgery and on other tests.
Stage 0 (carcinoma in situ). There are 3 types of breast carcinoma in situ:
- Ductal carcinoma in situ (DCIS) is a noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues. At this time, there is no way to know which lesions could become invasive.
- Lobular carcinoma in situ (LCIS) is a condition in which abnormal cells are found in the lobules of the breast. This condition seldom becomes invasive cancer.
- Paget disease of the nipple is a condition in which abnormal cells are found in the nipple only.
Stage I. In stage I, cancer has formed. Stage I is divided into stages IA and IB.
- In stage IA, the tumor is 2 centimeters or smaller. Cancer has not spread outside the breast.
- In stage IB, small clusters of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes and either:
- no tumor is found in the breast; or
- the tumor is 2 centimeters or smaller.
Stage II. Stage II is divided into stages IIA and IIB.
- In stage IIA:
- no tumor is found in the breast or the tumor is 2 centimeters or smaller. Cancer (larger than 2 millimeters) is found in 1-3 axillary lymph nodes or in the lymph nodes near the breastbone (found during a sentinel lymph node biopsy); or
- the tumor is larger than 2 centimeters but not larger than 5 centimeters. Cancer has not spread to the lymph nodes.
- In stage IIB, the tumor is:
- larger than 2 centimeters but not larger than 5 centimeters. Small clusters of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes; or
- larger than 2 centimeters but not larger than 5 centimeters. Cancer has spread to 1-3 axillary lymph nodes or to the lymph nodes near the breastbone (found during a sentinel lymph node biopsy); or
- larger than 5 centimeters. Cancer has not spread to the lymph nodes.
Stage IIIA. In stage IIIA:
- no tumor is found in the breast or the tumor may be any size. Cancer is found in 4-9 axillary lymph nodes or in the lymph nodes near the breastbone (found during imaging tests or a physical exam); or
- the tumor is larger than 5 centimeters. Small clusters of breast cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes; or
- the tumor is larger than 5 centimeters. Cancer has spread to 1-3 axillary lymph nodes or to the lymph nodes near the breastbone (found during a sentinel lymph node biopsy).
Stage IIIB. In stage IIIB, the tumor may be any size and cancer has spread to the chest wall and/or to the skin of the breast and caused swelling or an ulcer. Also, cancer may have spread to:
- up to 9 axillary lymph nodes; or
- the lymph nodes near the breastbone.
Cancer that has spread to the skin of the breast may also be inflammatory breast cancer.
Stage IIIC. In stage IIIC, no tumor is found in the breast or the tumor may be any size. Cancer may have spread to the skin of the breast and caused swelling or an ulcer and/or has spread to the chest wall. Also, cancer has spread to:
- 10 or more axillary lymph nodes; or
- lymph nodes above or below the collarbone; or
- axillary lymph nodes and lymph nodes near the breastbone.
Cancer that has spread to the skin of the breast may also be inflammatory breast cancer.
Stage IV. In stage IV, cancer has spread to other organs of the body, most often the bones, lungs, liver, or brain.
The treatment of breast cancer depends partly on the stage of the disease.
What Are the Standard Treatments Available for Women with Breast Cancer?
Five types of standard treatment are used:
Most patients with breast cancer have surgery to remove the cancer.
Sentinel lymph node biopsy is the removal of the sentinel lymph node during surgery. The sentinel lymph node is the first lymph node to receive lymphatic drainage from a tumor. It is the first lymph node where the cancer is likely to spread. A radioactive substance and/or blue dye is injected near the tumor. The substance or dye flows through the lymph ducts to the lymph nodes. The first lymph node to receive the substance or dye is removed. A pathologist views the tissue under a microscope to look for cancer cells. After the sentinel lymph node biopsy, the surgeon removes the tumor using breast-conserving surgery or mastectomy. If cancer cells were not found in the sentinel lymph node, it may not be necessary to remove more lymph nodes. If cancer cells were found, more lymph nodes will be removed through a separate incision. This is called a lymph node dissection.
Types of surgery include the following:
- Breast-conserving surgery (BCS) is an operation to remove the cancer and some normal tissue around it, but not the breast itself. Part of the chest wall lining may also be removed if the cancer is near it. This type of surgery may also be called lumpectomy, partial mastectomy, segmental mastectomy, quadrantectomy, or breast-sparing surgery.
- Total mastectomy: Surgery to remove the whole breast that has cancer. This procedure is also called a simple mastectomy. Some of the lymph nodes under the arm may be removed and checked for cancer. This may be done at the same time as the breast surgery or after. This is done through a separate incision.
- Modified radical mastectomy: Surgery to remove the whole breast that has cancer, many of the lymph nodes under the arm, the lining over the chest muscles, and sometimes, part of the chest wall muscles.
Chemotherapy may be given before surgery to remove the tumor. When given before surgery, chemotherapy will shrink the tumor and reduce the amount of tissue that needs to be removed during surgery. Treatment given before surgery is called preoperative therapy or neoadjuvant therapy.
Even if the doctor removes all the cancer that can be seen at the time of the surgery, some patients may be given radiation therapy, chemotherapy, or hormone therapy after surgery, to kill any cancer cells that are left. Treatment given after the surgery, to lower the risk that the cancer will come back, is called postoperative therapy or adjuvant therapy.
If a patient is going to have a mastectomy, breast reconstruction (surgery to rebuild a breast's shape after a mastectomy) may be considered. Breast reconstruction may be done at the time of the mastectomy or at some time after. The reconstructed breast may be made with the patient's own (nonbreast) tissue or by using implants filled with saline or silicone gel. Before the decision to get an implant is made, patients can call the U.S. Food and Drug Administration's (FDA) Center for Devices and Radiologic Health (CDRH) at 888-INFO-FDA (888-463-6332).
Radiation therapy is a cancer treatment that uses high-energy X-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy:
- External radiation therapy uses a machine outside the body to send radiation toward the cancer.
- Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer.
The way the radiation therapy is given depends on the type and stage of the cancer being treated. External radiation therapy is used to treat breast cancer. Internal radiation therapy with strontium-89 (a radionuclide) is used to relieve bone pain caused by breast cancer that has spread to the bones. Strontium-89 is injected into a vein and travels to the surface of the bones. Radiation is released and kills cancer cells in the bones.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the cerebrospinal fluid, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy).
The way the chemotherapy is given depends on the type and stage of the cancer being treated. Systemic chemotherapy is used in the treatment of breast cancer.
Hormone therapy is a cancer treatment that removes hormones or blocks their action and stops cancer cells from growing. Hormones are substances made by glands in the body and circulated in the bloodstream. Some hormones can cause certain cancers to grow. If tests show that the cancer cells have places where hormones can attach (receptors), drugs, surgery, or radiation therapy is used to reduce the production of hormones or block them from working. The hormone estrogen, which makes some breast cancers grow, is made mainly by the ovaries. Treatment to stop the ovaries from making estrogen is called ovarian ablation.
Hormone therapy with tamoxifen is often given to patients with early localized breast cancer that can be removed by surgery and those with metastatic breast cancer (cancer that has spread to other parts of the body). Hormone therapy with tamoxifen or estrogens can act on cells all over the body and may increase the chance of developing endometrial cancer. Women taking tamoxifen should have a pelvic exam every year to look for any signs of cancer. Any vaginal bleeding, other than menstrual bleeding, should be reported to a doctor as soon as possible.
Hormone therapy with a luteinizing hormone-releasing hormone (LHRH) agonist is given to some premenopausal women who have just been diagnosed with hormone receptor positive breast cancer. LHRH agonists decrease the body's estrogen and progesterone.
Hormone therapy with an aromatase inhibitor is given to some postmenopausal women who have hormone receptor positive breast cancer. Aromatase inhibitors decrease the body's estrogen by blocking an enzyme called aromatase from turning androgen into estrogen. Anastrozole, letrozole, and exemestane are types of aromatase inhibitors.
For the treatment of early localized breast cancer that can be removed by surgery, certain aromatase inhibitors may be used as adjuvant therapy instead of tamoxifen or after 2-3 years of tamoxifen use. For the treatment of metastatic breast cancer, aromatase inhibitors are being tested in clinical trials to compare them to hormone therapy with tamoxifen.
Other types of hormone therapy include megestrol acetate or anti-estrogen therapy such as fulvestrant.
Targeted therapy is a type of treatment that uses drugs or other substances to identify and attack specific cancer cells without harming normal cells. Monoclonal antibodies, tyrosine kinase inhibitors, cyclin-dependent kinase inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and poly ADP (adenosine diphosphate) ribose polymerase (PARP) inhibitors are types of targeted therapies used in the treatment of breast cancer.
Monoclonal antibody therapy is a cancer treatment that uses antibodies made in the laboratory, from a single type of immune system cell. These antibodies can identify substances on cancer cells or normal substances that may help cancer cells grow. The antibodies attach to the substances and kill the cancer cells, block their growth, or keep them from spreading. Monoclonal antibodies are given by infusion. They may be used alone or to carry drugs, toxins, or radioactive material directly to cancer cells. Monoclonal antibodies may be used in combination with chemotherapy as adjuvant therapy.
Types of monoclonal antibody therapy include the following:
- Trastuzumab is a monoclonal antibody that blocks the effects of the growth factor protein HER2, which sends growth signals to breast cancer cells. It may be used with other therapies to treat HER2 positive breast cancer.
- Pertuzumab is a monoclonal antibody that may be combined with trastuzumab and chemotherapy to treat breast cancer. It may be used to treat certain patients with HER2 positive breast cancer that has metastasized (spread to other parts of the body). It may also be used as neoadjuvant therapy in certain patients with early stage HER2 positive breast cancer.
- Ado-trastuzumab emtansine is a monoclonal antibody linked to an anticancer drug. This is called an antibody-drug conjugate. It is used to treat HER2 positive breast cancer that has spread to other parts of the body or recurred (come back).
Tyrosine kinase inhibitors are targeted therapy drugs that block signals needed for tumors to grow. Tyrosine kinase inhibitors may be used with other anticancer drugs as adjuvant therapy. Tyrosine kinase inhibitors include the following:
- Lapatinib is a tyrosine kinase inhibitor that blocks the effects of the HER2 protein and other proteins inside tumor cells. It may be used with other drugs to treat patients with HER2 positive breast cancer that has progressed after treatment with trastuzumab.
- Neratinib is a tyrosine kinase inhibitor that blocks the effects of the HER2 protein and other proteins inside tumor cells. It may be used to treat patients with early stage HER2 positive breast cancer after treatment with trastuzumab.
Cyclin-dependent kinase inhibitors (CDKIs) are targeted therapy drugs that block proteins called cyclin-dependent kinases, which cause the growth of cancer cells. Cyclin-dependent kinase inhibitors include the following:
- Palbociclib is a cyclin-dependent kinase inhibitor used with the drug letrozole to treat breast cancer that is estrogen receptor positive and HER2 negative and has spread to other parts of the body. It is used in postmenopausal women whose cancer has not been treated with hormone therapy. Palbociclib may also be used with fulvestrant in women whose disease has gotten worse after treatment with hormone therapy.
- Ribociclib is a cyclin-dependent kinase inhibitor used with letrozole to treat breast cancer that is hormone receptor positive and HER2 negative and has come back or spread to other parts of the body. It is used in postmenopausal women whose cancer has not been treated with hormone therapy.
- Abemaciclib is a cyclin-dependent kinase inhibitor used to treat hormone receptor positive and HER2 negative breast cancer that is advanced or has spread to other parts of the body. It may be used alone or with other drugs to treat breast cancer that has gotten worse after other treatment.
Mammalian target of rapamycin (mTOR) inhibitors block a protein called mTOR, which may keep cancer cells from growing and prevent the growth of new blood vessels that tumors need to grow. mTOR inhibitors include the following:
- Everolimus is an mTOR inhibitor used in postmenopausal women with advanced hormone receptor positive breast cancer that is also HER2 negative and has not gotten better with other treatment.
PARP inhibitors are a type of targeted therapy that block deoxyribonucleic acid (DNA) repair and may cause cancer cells to die. PARP inhibitor therapy is being studied for the treatment of patients with triple negative breast cancer or tumors with BRCA1 or BRCA2 mutations.
Side Effects of Treatment
Treatment for breast cancer may cause side effects. Some treatments for breast cancer may cause side effects that continue or appear months or years after treatment has ended. These are called late effects. Late effects of radiation therapy are not common, but may include:
- Inflammation of the lung after radiation therapy to the breast, especially when chemotherapy is given at the same time
- Arm lymphedema, especially when radiation therapy is given after lymph node dissection
- In women younger than 45 years who receive radiation therapy to the chest wall after mastectomy, there may be a higher risk of developing breast cancer in the other breast
Late effects of chemotherapy depend on the drugs used, but may include:
- Heart failure
- Blood clots
- Premature menopause
- Second cancer, such as leukemia
Late effects of targeted therapy with trastuzumab, lapatinib, or pertuzumab may include:
- Heart problems such as heart failure
What Is the Prognosis for Breast Cancer in Women?
The prognosis (chance of recovery) and treatment options depend on the following:
- The stage of the cancer (the size of the tumor and whether it is in the breast only or has spread to lymph nodes or other places in the body)
- The type of breast cancer
- Estrogen receptor and progesterone receptor levels in the tumor tissue
- Human epidermal growth factor type 2 receptor (HER2/neu) levels in the tumor tissue
- Whether the tumor tissue is triple negative (cells that do not have estrogen receptors, progesterone receptors, or high levels of HER2/neu)
- How fast the tumor is growing
- How likely the tumor is to recur (come back)
- A woman's age, general health, and menopausal status (whether a woman is still having menstrual periods)
- Whether the cancer has just been diagnosed or has recurred (come back)