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Cancer Types

Types of Cancer > Breast Cancer > Overview

Breast Cancer: What is Breast Cancer?

Affiliation: National Cancer Institute
Last Modified: November 1, 2001

Description

Note: Separate PDQ summaries on Screening for Breast Cancer; Prevention of Breast Cancer; and Male Breast Cancer Treatment are also available.

What is breast cancer?

Breast cancer, a common cancer in women, is a disease in which cancer(malignant) cells are found in the tissues of the breast. 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. The most common type of breast cancer is ductal cancer. It is found in the cells of the ducts. Cancer that begins in the lobes or lobules is called lobular cancer. Lobular cancer is more often found in both breasts than other types of breast cancer. Inflammatory breast cancer is an uncommon type of breast cancer. In this disease, the breast is warm, red, and swollen.

Hereditary breast cancer makes up approximately 5% to 10% of all breast cancer cases. The genes in cells carry the hereditary information that is received from a person's parents. Several genes have been found to be defective in some breast cancer patients. Relatives of breast cancer patients who carry these defective genes may be more likely to develop breast or ovarian cancer. Some defective genes are more common in certain ethnic groups. Tests are being developed to determine who has the genetic defect long before any cancer appears. (Refer to the PDQ summaries on Screening for Breast Cancer and Prevention of Breast Cancer for more information.)

Hormonal contraceptives may be another factor to consider. Research findings suggest a link between contraceptive use and a slightly increased risk of developing breast cancer.

A doctor should be seen if changes in the breasts are noticed. The doctor may suggest that you have a mammogram. A mammogram is a special x-ray of the breast that may find tumors that are too small to feel. If a lump in the breast is found, the doctor may need to cut out a small piece of the lump and look at it under the microscope to see if there are any cancer cells. This procedure is called a biopsy. Sometimes the biopsy is done by inserting a needle into the breast and drawing out some of the tissue. If the biopsy shows that there is cancer, it is important that certain tests (called estrogen and progesterone receptor tests) be done on the cancer cells.

Estrogen and progesterone receptor tests may tell whether hormones affect the way the cancer grows. They may also give information about the chances of the tumor coming back (recurring). The results help a doctor decide whether to use hormone therapy to stop the cancer from growing. Tissue from the tumor needs to be taken to the laboratory for estrogen and progesterone tests at the time of biopsy because it may be hard to get enough cancer cells later, although newer techniques can be used on tissue that is not fresh.

The chance of recovery (prognosis) and choice of treatment depend on the stage of the cancer (whether it is just in the breast or has spread to other places in the body), the type of breast cancer, certain characteristics of the cancer cells, and whether the cancer is found in the other breast. A woman's age,weight, menopausal status (whether or not a woman is still having menstrual periods), and general health can also affect the prognosis and choice of treatment.

If a patient is going to have a mastectomy, breast reconstruction (making a new breast mound) may be considered. It may be done at the time of the mastectomy or at some future time. The breast may be made with the patient's own(non-breast) tissue or by using implants. Different types of implants can be used. The Food and Drug Administration (FDA) has announced that breast implants filled with silicone gel may only be used in clinical trials. Saline-filled breast implants, which contain saltwater rather than silicone gel, may also be used. Before the decision to get an implant is made, patients can call the FDA's Center for Devices and Radiologic Health at 1-888-INFO-FDA(1-888-463- 6332) to obtain additional information. Additional questions can then be discussed with a doctor.

Stage explanation

Stages of breast cancer
Once breast cancer has been found, more tests will be done to find out if the cancer has spread from the breast to other parts of the body. This is called staging. To plan treatment, a doctor needs to know the stage of the disease. The following stages are used for breast cancer.

Stage 0
Ductal carcinoma in situ (DCIS; also known as intraductal carcinoma) is a very early breast cancer that may develop into an invasive (cancer that has spread from the duct into surrounding tissues) type of breast cancer.

Lobular carcinoma in situ (LCIS) is not cancer, but rather a marker that identifies a woman at increased risk to develop invasive (cancer that has spread into surrounding tissues) breast cancer later in life.

Stage I
The cancer is no larger than 2 centimeters (about 1 inch) and has not spread outside the breast.

Stage II
Stage II is divided into stages IIA and IIB.

Stage IIA is defined by either of the following:

The cancer is no larger than 2 centimeters but has spread to the lymph nodes under the arm (the axillary lymph nodes).

The cancer is between 2 and 5 centimeters (from 1 to 2 inches), but has not spread to the lymph nodes under the arm.

Stage IIB is defined by either of the following:

The cancer is between 2 and 5 centimeters (from 1 to 2 inches), and has spread to the lymph nodes under the arm.

The cancer is larger than 5 centimeters (larger than 2 inches), but has not spread to the lymph nodes under the arm.

Stage III
Stage III is divided into stages IIIA and IIIB.

Stage IIIA is defined by either of the following:

The cancer is smaller than 5 centimeters and has spread to the lymph nodes under the arm, and the lymph nodes are attached to each other or to other structures.

The cancer is larger than 5 centimeters and has spread to the lymph nodes under the arm.

Stage IIIB is defined by either of the following:

The cancer has spread to tissues near the breast (skin or chest wall, including the ribs and the muscles in the chest).

The cancer has spread to lymph nodes inside the chest wall along the breast bone.

Stage IV
The cancer has spread to other organs of the body, most often the bones, lungs, liver, or brain. Or, tumor has spread locally to the skin and lymph nodes inside the neck, near the collarbone.

Inflammatory breast cancer
Inflammatory breast cancer is a special class of breast cancer that is rare. The breast looks as if it is inflamed because of its red appearance and warmth.

The skin may show signs of ridges and wheals or it may have a pitted appearance. Inflammatory breast cancer tends to spread quickly.

Recurrent
Recurrent disease means that the cancer has come back (recurred) after it has been treated. It may come back in the breast, in the soft tissues of the chest (the chest wall), or in another part of the body.