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. The lobes and lobules are connected by thin tubes called ducts.
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Each breast also contains blood vessels and lymph vessels. The lymph vessels carry an almost colorless fluid called lymph. The lymph vessels lead to small, bean-shaped organs called lymph nodes that help the body fight infection and disease. Lymph nodes are found throughout the body. 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 sometimes detected (found) in women who are pregnant or have just given birth.
In women who are pregnant or who have just given birth, breast cancer occurs most often between the ages of 32 and 38. Breast cancer occurs about once in every 3,000 pregnancies.
It may be difficult to detect (find) breast cancer early in pregnant or nursing women, whose breasts are often tender and swollen.
Women who are pregnant, nursing, or have just given birth usually have tender, swollen breasts. This can make small lumps difficult to detect and may lead to delays in diagnosing breast cancer. Because of these delays, cancers are often found at a later stage in these women.
Breast examination should be part of prenatal and postnatal care.
To detect breast cancer, pregnant and nursing women should examine their breasts themselves. Women should also receive clinical breast examinations during their routine prenatal and postnatal examinations.
Tests that examine the breasts are used to detect (find) and diagnose breast cancer.
If an abnormality is found, one or all of the following tests may be used:
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Certain factors affect prognosis (chance of recovery) and treatment options.
The prognosis (chance of recovery) and treatment options depend on the following:
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 process used to find out if 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. (Refer to the PDQ summary on Breast Cancer Treatment for more information on the stages used for breast cancer.)
Methods used to stage breast cancer can be changed to make them safer for the fetus.
Standard methods for giving imaging scans can be adjusted so that the fetus is exposed to less radiation. Tests to measure the level of hormones in the blood may also be used in the staging process.
There are different types of treatment for patients with breast cancer.
Different types of treatment are available for patients with breast cancer. Some treatments are standard (the currently used treatment), and some are being tested in clinical trials. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment.
For some patients, taking part in a clinical trial may be the best treatment choice. Many of today's standard treatments for cancer are based on earlier clinical trials. Patients who take part in a clinical trial may receive the standard treatment or be among the first to receive a new treatment.
Patients who take part in clinical trials also help improve the way cancer will be treated in the future. Even when clinical trials do not lead to effective new treatments, they often answer important questions and help move research forward.
Some clinical trials only include patients who have not yet received treatment. Other trials test treatments for patients whose cancer has not gotten better. There are also clinical trials that test new ways to stop cancer from recurring (coming back) or reduce the side effects of cancer treatment.
Clinical trials are taking place in many parts of the country. Information about clinical trials is available from the NCI Web site.
Treatment options for pregnant women depend on the stage of the disease and the age of the fetus.
Three types of standard treatment are used:
Surgery
Most pregnant women with breast cancer have surgery to remove the breast. Some of the lymph nodes under the arm are usually taken out and looked at under a microscope to see if they contain cancer cells.
Types of surgery to remove the breast include:
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Breast-conserving surgery, an operation to remove the cancer but not the breast itself, includes the following:
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Even if the doctor removes all of the cancer that can be seen at the time of surgery, the patient may be given radiation therapy, chemotherapy, or hormone therapy after surgery to try to kill any cancer cells that may be left. Treatment given after surgery to increase the chances of a cure is called adjuvant therapy.
Radiation therapy
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells. 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.
Radiation therapy should not be given to pregnant women with early stage (stage I or II) breast cancer because it can harm the fetus. For women with late stage (stage III or IV) breast cancer, it should not be given during the first 3 months of pregnancy.
Chemotherapy
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells 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 spinal column, 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.
Chemotherapy should not be given during the first 3 months of pregnancy. Chemotherapy given after this time does not usually harm the fetus but may cause early labor and low birth weight.
New types of treatment are being tested in clinical trials.
This summary section describes treatments that are being studied in clinical trials. It may not mention every new treatment being studied. Information about clinical trials is available from the NCI Web site.
Hormone therapy
Hormone therapy is a cancer treatment that removes hormones or blocks their action and stops cancer cells from growing. Hormones are substances produced 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 are used to reduce the production of hormones or block them from working.
The effectiveness of hormone therapy, alone or combined with chemotherapy, in treating breast cancer in pregnant women is not yet known.
Ending the pregnancy does not seem to improve the mother’s chance of survival and is not usually a treatment option.
If the cancer must be treated with chemotherapy and radiation therapy, which may harm the fetus, ending the pregnancy is sometimes considered. This decision may depend on the stage of cancer, the age of the fetus, and the mother’s chance of survival.
Treatment of early stage breast cancer (stage I and stage II) may be surgery followed by adjuvant therapy as follows:
Treatment of late stage breast cancer (stage III and stage IV) may include the following:
Radiation therapy and chemotherapy should not be given during the first 3 months of pregnancy.
Lactation (breast milk production) and breast-feeding should be stopped if surgery or chemotherapy is planned.
If surgery is planned, breast-feeding should be stopped to reduce blood flow in the breasts and make them smaller. Breast-feeding should also be stopped if chemotherapy is planned. Many anticancer drugs, especially cyclophosphamide and methotrexate, may occur in high levels in breast milk and may harm the nursing baby. Women receiving chemotherapy should not breast-feed. Stopping lactation does not improve survival of the mother.
Breast cancer does not appear to harm the fetus.
Breast cancer cells do not seem to pass from the mother to the fetus.
Pregnancy does not seem to affect the survival of women who have had breast cancer in the past.
Some doctors recommend that a woman wait 2 years after treatment for breast cancer before trying to have a baby, so that any early return of the cancer would be detected. This may affect a woman’s decision to become pregnant. The fetus does not seem to be affected if the mother has previously had breast cancer.
Effects of certain cancer treatments on later pregnancies are not known.
The effects of treatment with high-dose chemotherapy and a bone marrow transplant, with or without radiation therapy, on later pregnancies are not known.
For more information from the National Cancer Institute about breast cancer and pregnancy, see the following:
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The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Several enhancements have been made to this summary to better explain certain medical concepts and to give readers more information about clinical trials. The following changes were made: