Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast.
The breast is made up of lobes and ducts. Each breast has 15 to 20 sections called lobes, which have many smaller sections called lobules. Lobules end in dozens of tiny bulbs that can produce milk. The lobes, lobules, and bulbs are linked by thin tubes called ducts.
Anatomy of the female breast. The nipple and areola are shown on the outside of the breast. The lymph nodes, lobes, lobules, ducts, and other parts of the inside of the breast are also shown.
Each breast also has blood vessels and lymph vessels. The lymph vessels carry an almost colorless fluid called lymph. Lymph vessels lead to organs called lymph nodes. Lymph nodes are small bean-shaped structures that are found throughout the body. They filter substances in a fluid called 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.
Age and health history can affect the risk of developing breast cancer.
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. People who think they may be at risk should discuss this with their doctor. Risk factors for breast cancer include the following:
NCI'sBreast Cancer Risk Assessment Tool uses a woman's risk factors to estimate her risk for breast cancer during the next five years and up to age 90. This online tool is meant to be used by a health care provider. For more information on breast cancer risk, call 1-800-4-CANCER.
Breast cancer is sometimes caused by inherited gene mutations (changes).
The genes in cells carry the hereditary information that is received from a person’s parents. Hereditary breast cancer makes up approximately 5% to 10% of all breast cancer. Some altered genes related to breast cancer are more common in certain ethnic groups.
Women who have an altered gene related to breast cancer and who have had breast cancer in one breast have an increased risk of developing breast cancer in the other breast. These women also have an increased risk of developing ovarian cancer, and may have an increased risk of developing other cancers. Men who have an altered gene related to breast cancer also have an increased risk of developing this disease. For more information, see the PDQ summary on Male Breast Cancer Treatment.
Tests have been developed that can detect altered genes. These genetic tests are sometimes done for members of families with a high risk of cancer. See the following PDQ summaries for more information:
Possible signs of breast cancer include a lump or change in the breast.
Breast cancer may cause any of the following signs and symptoms. Check with your doctor if any of the following problems occur:
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 that is around the nipple).
Dimples in the breast that look like the skin of an orange, called peau d’orange.
Other conditions that are not breast cancer may cause these same symptoms.
Tests that examine the breasts are used to detect (find) and diagnose breast cancer.
A doctor should be seen if changes in the breast are noticed. 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.
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.
MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. 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 in the organ or tissue that makes it.
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, the doctor may need to remove a small piece of the lump. Four types of biopsies are as follows:
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 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 (Herceptin) and lapatinib (Tykerb).
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).
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 of the cancer spreading is high, chemotherapy may be given to lower the risk.
Certain factors affect prognosis (chance of recovery) and treatment options.
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).
Whether the cancer has just been diagnosed or has recurred (come back).
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