Breast Cancer

General Information | Treatment Options | Screening | Additional Resources

General Information
  • About
  • Risk Factors
  • Detection
  • Stages

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.

Breast anatomy; drawing shows lobes, lobules, ducts, areola, nipple, fat, lymph nodes, and lymph vessels Anatomy of the breast, showing lymph nodes and lymph vessels.

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.

Learn about inflammatory 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. Risk factors for breast cancer include the following:

  • Older age.

  • Menstruating at an early age.

  • Older age at first birth or never having given birth.

  • A personal history of breast cancer or benign (noncancer) breast disease.

  • A mother or sister with breast cancer.

  • Treatment with radiation therapy to the breast/chest.

  • Breast tissue that is dense on a mammogram.

  • Taking hormones such as estrogen and progesterone.

  • Drinking alcoholic beverages.

  • Being white.

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:

  • Breast Cancer Screening

  • Breast Cancer Prevention

  • Genetics of Breast and Ovarian Cancer

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:

  • Mammogram: An x-ray of the breast.

  • Photograph shows the right breast positioned between the plates of a mammography machine. Mammography of the right breast.

  • 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:

    • Excisional biopsy: The removal of an entire lump of tissue.

    • Incisional biopsy: The removal of part of a lump or a sample of tissue.

    • Core biopsy: The removal of tissue using a wide needle.

    • Fine-needle aspiration (FNA) biopsy: The removal of tissue or fluid, using a thin needle.

  • Estrogen and progesterone receptor test: A test to measure the amount of estrogen and progesterone (hormones) receptors in cancer tissue. If cancer is found in the breast, tissue from the tumor is checked in the laboratory to find out whether estrogen and progesterone could affect the way cancer grows. The test results show whether hormone therapy may stop the cancer from growing.

  • 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).

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.

  • Whether the cells have high levels of human epidermal growth factor type 2 receptors (HER2/neu).

  • How fast the tumor is growing.

  • A woman's age, general health, and menopausal status (whether a woman is still having menstrual periods).

  • Whether the cancer has just been diagnosed or has recurred (come back).

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 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.

There are three ways that cancer spreads in the body.

The three ways that cancer spreads in the body are:

  • Through tissue. Cancer invades the surrounding normal tissue.

  • Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.

  • Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.

When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.

The following stages are used for breast cancer:Stage 0 (carcinoma in situ)

There are 2 types of breast carcinoma in situ:

  • Ductal carcinoma in situ (DCIS) is a noninvasive condition in which abnormal cells are found in the lining of a breast duct. The abnormal cells have not spread outside the duct to other tissues in the breast. In some cases, DCIS may become invasive cancer and spread to other tissues, although it is not known at this time how to predict which lesions will become invasive.

  • Lobular carcinoma in situ (LCIS) is a condition in which abnormal cells are found in the lobules of the breast. This condition seldom becomes invasive cancer; however, having lobular carcinoma in situ in one breast increases the risk of developing breast cancer in either breast.

Stage I

In stage I, cancer has formed. The tumor is 2 centimeters or smaller and has not spread outside the breast.

Stage IIA

In stage IIA:

  • no tumor is found in the breast, but cancer is found in the axillary lymph nodes (the lymph nodes under the arm); or

  • the tumor is 2 centimeters or smaller and has spread to the axillary lymph nodes; or

  • the tumor is larger than 2 centimeters but not larger than 5 centimeters and has not spread to the axillary lymph nodes.

Stage IIB

In stage IIB, the tumor is either:

  • larger than 2 centimeters but not larger than 5 centimeters and has spread to the axillary lymph nodes; or

  • larger than 5 centimeters but has not spread to the axillary lymph nodes.

Stage IIIA

In stage IIIA:

  • no tumor is found in the breast. Cancer is found in axillary lymph nodes that are attached to each other or to other structures, or cancer may be found in lymph nodes near the breastbone; or

  • the tumor is 2 centimeters or smaller. Cancer has spread to axillary lymph nodes that are attached to each other or to other structures, or cancer may have spread to lymph nodes near the breastbone; or

  • the tumor is larger than 2 centimeters but not larger than 5 centimeters. Cancer has spread to axillary lymph nodes that are attached to each other or to other structures, or cancer may have spread to lymph nodes near the breastbone; or

  • the tumor is larger than 5 centimeters. Cancer has spread to axillary lymph nodes that may be attached to each other or to other structures, or cancer may have spread to lymph nodes near the breastbone.

Stage IIIB

In stage IIIB, the tumor may be any size and cancer:

  • has spread to the chest wall and/or the skin of the breast; and

  • may have spread to axillary lymph nodes that may be attached to each other or to other structures, or cancer may have spread to lymph nodes near the breastbone.

Cancer that has spread to the skin of the breast is inflammatory breast cancer. See the section on Inflammatory Breast Cancer for more information.

Stage IIIC

In stage IIIC, there may be no sign of cancer in the breast or the tumor may be any size and may have spread to the chest wall and/or the skin of the breast. Also, cancer:

  • has spread to lymph nodes above or below the collarbone; and

  • may have spread to axillary lymph nodes or to lymph nodes near the breastbone.

Cancer that has spread to the skin of the breast is inflammatory breast cancer. See the section on Inflammatory Breast Cancer for more information.

Stage IIIC breast cancer is divided into operable and inoperable stage IIIC.

In operable stage IIIC, the cancer:

  • is found in ten or more axillary lymph nodes; or

  • is found in lymph nodes below the collarbone; or

  • is found in axillary lymph nodes and in lymph nodes near the breastbone.

In inoperable stage IIIC breast cancer, the cancer has spread to the lymph nodes above the collarbone.

Stage IV

In stage IV, the cancer has spread to other organs of the body, most often the bones, lungs, liver, or brain.

Recurrent Breast Cancer

Recurrent breast cancer is cancer that has recurred (come back) after it has been treated. The cancer may come back in the breast, in the chest wall, or in other parts of the body.

Learn about inflammatory breast cancer.

 

Cancer information from the NCI PDQ service