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.
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.
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:
Older age is the main risk factor for most cancers. The chance of getting cancer increases as you get older.
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.
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:
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:
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:
There are four types of biopsy used to check for breast cancer:
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:
Tests include the following:
There are many types of multigene tests. The following multigene tests have been studied in clinical trials:
Based on these tests, breast cancer is described as one of the following types:
This information helps the doctor decide which treatments will work best for your 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:
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:
Stage I. In stage I, cancer has formed. Stage I is divided into stages IA and IB.
Stage II. Stage II is divided into stages IIA and IIB.
Stage IIIA. In stage IIIA:
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:
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:
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.
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:
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:
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:
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:
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:
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:
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.
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:
Late effects of chemotherapy depend on the drugs used, but may include:
Late effects of targeted therapy with trastuzumab, lapatinib, or pertuzumab may include:
The prognosis (chance of recovery) and treatment options depend on the following: