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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.
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.
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.
See the PDQ summary on Unusual Cancers of Childhood for information about childhood breast cancer.
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:
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:
Estrogen and progesterone receptor 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 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 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).