The breast is made up of lobes and ducts. Each breast has 15 to 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.
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 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.Sometimes breast cancer occurs in women who are pregnant or have just given birth.
Breast cancer occurs about once in every 3,000 pregnancies. It occurs most often in women aged 32 to 38 years. Because many women are choosing to delay having children, it is likely that the number of new cases of breast cancer during pregnancy will increase.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:
The breasts usually get larger, tender, or lumpy in women who are pregnant, nursing, or have just given birth. This occurs because of normal hormone changes that take place during pregnancy. These changes can make small lumps difficult to detect. The breasts may also become denser. It is more difficult to detect breast cancer in women with dense breasts using mammography. Because these breast changes can delay diagnosis, breast cancer is often found at a later stage in these women.Breast exams 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 exams during their regular prenatal and postnatal check-ups. Talk to your doctor if you notice any changes in your breasts that you do not expect or that worry you.Tests that examine the breasts are used to detect (find) and diagnose breast cancer.
The following tests and procedures may be used:
There are four types of breast biopsies:
Decisions about the best treatment are based on the results of these tests and the age of the unborn baby. The tests give information about:
Tests may include the following:
The prognosis (chance of recovery) and treatment options depend on the following:
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.
Some procedures may expose the unborn baby to harmful radiation or dyes. These procedures are done only if absolutely necessary. Certain actions can be taken to expose the unborn baby to as little radiation as possible, such as the use of a lead-lined shield to cover the abdomen.
The following tests and procedures may be used to stage breast cancer during pregnancy:
Cancer can spread through tissue, the lymph system, and the blood:
When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.
The metastatic tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bone, the cancer cells in the bone are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.<EmbeddedVideo><VideoTitle>metastasis: how cancer spreads</VideoTitle></EmbeddedVideo>The following stages are used for breast cancer:
This section describes the stages of breast cancer. The breast cancer stage is based on the results of testing that is done on the tumor and lymph nodes removed during surgery and other tests.Stage 0 (carcinoma in situ)
There are 3 types of breast carcinoma in situ:
Stage I breast cancer. In stage IA, the tumor is 2 centimeters or smaller and has not spread outside the breast. In stage IB, no tumor is found in the breast or the tumor is 2 centimeters or smaller. Small clusters of cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes.
In stage I, cancer has formed. Stage I is divided into stages IA and IB.
Stage II is divided into stages IIA and IIB.
Stage IIA breast cancer. No tumor is found in the breast and cancer is found in 1 to 3 axillary lymph nodes or lymph nodes near the breastbone (left panel); OR the tumor is 2 centimeters or smaller and cancer is found in 1 to 3 axillary lymph nodes or lymph nodes near the breastbone (middle panel); OR the tumor is larger than 2 centimeters but not larger than 5 centimeters and has not spread to the lymph nodes (right panel).
Stage IIB breast cancer. The tumor is larger than 2 centimeters but not larger than 5 centimeters and small clusters of cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes (left panel); OR the tumor is larger than 2 centimeters but not larger than 5 centimeters and cancer is found in 1 to 3 axillary lymph nodes or lymph nodes near the breastbone (middle panel); OR the tumor is larger than 5 centimeters and has not spread to the lymph nodes (right panel).
Stage IIIA breast cancer. No tumor is found in the breast or the tumor may be any size and cancer is found in 4 to 9 axillary lymph nodes or lymph nodes near the breastbone (left panel); OR the tumor is larger than 5 centimeters and small clusters of cancer cells (larger than 0.2 millimeter but not larger than 2 millimeters) are found in the lymph nodes (middle panel); OR the tumor is larger than 5 centimeters and cancer is found in 1 to 3 axillary lymph nodes or lymph nodes near the breastbone (right panel).
In stage IIIA:
Stage IIIB breast cancer. 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. 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 be inflammatory breast cancer.
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
Stage IIIC breast cancer. No tumor is found in the breast or the tumor may be any size and may have spread to the chest wall and/or to the skin of the breast and caused swelling or an ulcer. Also, cancer has spread to 10 or more axillary lymph nodes (left panel); OR to lymph nodes above or below the collarbone (middle panel); OR to axillary lymph nodes and lymph nodes near the breastbone (right panel). Cancer that has spread to the skin of the breast may be inflammatory breast cancer.
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.
For treatment, stage IIIC breast cancer is divided into operable and inoperable cancer.Stage IV
Stage IV breast cancer. The cancer has spread to other parts of the body, such as the brain, lung, liver, or bone.
In stage IV, cancer has spread to other organs of the body, most often the bones, lungs, liver, or brain.
Most pregnant women with breast cancer have surgery to remove the breast. Some of the lymph nodes under the arm may be removed so they can be checked under a microscope by a pathologist for signs of cancer.
Types of surgery to remove the cancer include:
Breast-conserving surgery. The tumor and some normal tissue around it are removed, but not the breast itself. Some lymph nodes under the arm may be removed. Part of the chest wall lining may also be removed if the cancer is near it.
After the doctor removes all of the cancer that can be seen at the time of surgery, some patients may be given chemotherapy or radiation therapy after surgery to kill any cancer cells that are left. For pregnant women with early-stage breast cancer, radiation therapy and hormone therapy are given after the baby is born. Treatment given after surgery, to lower the risk that the cancer will come back, 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 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 may be given to pregnant women with early stage (stage I or II) breast cancer after the baby is born. Women with late stage (stage III or IV) breast cancer may be given external radiation therapy after the first 3 months of pregnancy or, if possible, radiation therapy is delayed until after the baby is born.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 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 to treat breast cancer during pregnancy.
Chemotherapy is usually not given during the first 3 months of pregnancy. Chemotherapy given after this time does not usually harm the unborn baby but may cause early labor or low birth weight.
See Drugs Approved for Breast Cancer for more information.Ending the pregnancy does not seem to improve the mother’s chance of survival.
Because ending the pregnancy is not likely to improve the mother’s chance of survival, it is not usually a treatment option.Treatment for breast cancer may cause side effects.
For information about side effects caused by treatment for cancer, see our Side Effects page.
For information about the treatments listed below, see the Treatment Option Overview section.
Pregnant women with early-stage breast cancer (stage I and stage II) are usually treated in the same way as patients who are not pregnant, with some changes to protect the unborn baby. Treatment may include the following:
Hormone therapy and trastuzumab should not be given during pregnancy.
There is no standard treatment for patients with late-stage breast cancer (stage III or stage IV) during pregnancy. Treatment may include the following:
Radiation therapy and chemotherapy should not be given during the first 3 months of pregnancy.
If surgery is planned, breast-feeding should be stopped to reduce blood flow in the breasts and make them smaller. Many chemotherapy 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 the mother's prognosis.Breast cancer does not appear to harm the unborn baby.
Breast cancer cells do not seem to pass from the mother to the unborn baby.Pregnancy does not seem to affect the survival of women who have had breast cancer in the past.
For women who have had breast cancer, pregnancy does not seem to affect their survival. However, 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 unborn baby does not seem to be affected if the mother has had breast cancer.
For more information from the National Cancer Institute about breast cancer during pregnancy, see the following:
For general cancer information and other resources from the National Cancer Institute, see the following:
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PDQ® Adult Treatment Editorial Board. PDQ Breast Cancer Treatment During Pregnancy. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/types/breast/patient/pregnancy-breast-treatment-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389161]
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Date last modified: 2018-03-28
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