Breast Cancer: What is Breast Cancer?

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National Cancer Institute
Last Modified: November 1, 2001

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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.

Treatment option overview

How breast cancer is treated

There are treatments for all patients with breast cancer. Four types of treatment are used: -

  • surgery (taking out the cancer in an operation) -
  • radiation therapy (using high-dose x-rays to kill cancer cells) -
  • chemotherapy (using drugs to kill cancer cells) - hormone therapy (using drugs that change the way hormones work or taking out organs that make hormones, such as the ovaries)

Biological therapy (using the body's immune system to fight cancer), bone marrow transplantation, and peripheral blood stem cell transplantation are being tested in clinical trials.

Most patients with breast cancer have surgery to remove the cancer from the breast. Usually, some of the lymph nodes under the arm are also taken out and looked at under a microscope to see if there are any cancer cells.

Different types of operations used:

Surgery to conserve the breast:

Lumpectomy (sometimes called excisional biopsy or wide excision) is the removal of the lump in the breast and some of the tissue around it. It is usually followed by radiation therapy to the part of the breast that remains. Most doctors also take out some of the lymph nodes under the arm.

Partial or segmental mastectomy is the removal of the cancer as well as some of the breast tissue around the tumor and the lining over the chest muscles below the tumor. Usually some of the lymph nodes under the arm are taken out. In most cases, radiation therapy follows.

Other types of surgery:

Total or simple mastectomy is the removal of the whole breast. Sometimes lymph nodes under the arm are also taken out.

Modified radical mastectomy is the removal of the breast, many of the lymph nodes under the arm, the lining over the chest muscles, and sometimes part of the chest wall muscles. This is the most common operation for breast cancer.

Radical mastectomy (also called the Halsted radical mastectomy) is the removal of the breast, chest muscles, and all of the lymph nodes under the arm. For many years, this was the operation most used, but it is used now only when the tumor has spread to the chest muscles.

Radiation therapy is the use of high-energy x-rays to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external radiation therapy) or from putting materials that produce radiation(radioisotopes) through thin plastic tubes into the area where the cancer cells are found (internal radiation therapy).

Chemotherapy is the use of drugs to kill cancer cells. Chemotherapy may be taken by mouth or it may be put into the body by inserting a needle into a vein or muscle. Chemotherapy is called a systemic treatment because the drugs enter the bloodstream, travel through the body, and can kill cancer cells outside the breast area.

If tests show that the breast cancer cells have estrogen receptors and progesterone receptors, hormone therapy may be given. Hormone therapy is used to change the way hormones in the body help cancers grow. This may be done by using drugs that change the way hormones work or by surgery to take out organs that make hormones, such as the ovaries. Hormone therapy with tamoxifen is often given to patients with early stages of breast cancer. Hormone therapy with tamoxifen or estrogens can act on cells all over the body and may increase the chance of getting cancer of the uterus. A doctor should be seen for a pelvic examination every year. Any vaginal bleeding, other than menstrual bleeding, should be reported to a doctor as soon as possible.

Even if the doctor removes all the cancer that can be seen at the time of the operation, the patient may be given radiation therapy, chemotherapy, or hormone therapy after surgery to try to kill any cancer cells that may be left. Therapy given after an operation when there are no cancer cells that can be seen is called adjuvant therapy.

Biological therapy tries to get the body to fight cancer. It uses materials made by the body or made in a laboratory to boost, direct, or restore the body's natural defenses against disease. Biological therapy is sometimes called biological response modifier (BRM) therapy or immunotherapy. This treatment is currently only being given in clinical trials.

Bone marrow transplantation is a type of treatment that is being studied in clinical trials. Sometimes breast cancer becomes resistant to treatment with radiation therapy or chemotherapy. Very high doses of chemotherapy may then be used to treat the cancer. Because the high doses of chemotherapy can destroy the bone marrow, marrow is taken from the bones before treatment. The marrow is then frozen and the patient is given high-dose chemotherapy with or without radiation therapy to treat the cancer. The marrow that was taken out is then thawed and given back to the patient through a needle inserted into a vein to replace the marrow that was destroyed. This type of transplant is called an autologous transplant. If the marrow that is given is taken from another person, the transplant is called an allogeneic transplant.

Another type of autologous transplant is called a peripheral blood stem cell transplant. The patient's blood is passed through a machine that removes the stem cells (immature cells from which all blood cells develop) and then returns the blood back to the patient. This procedure is called leukapheresis and usually takes 3 or 4 hours to complete. The stem cells are treated with drugs to kill any cancer cells and then frozen until they are transplanted back to the patient. This procedure may be done alone or with an autologous bone marrow transplant.

A greater chance for recovery occurs if the doctor chooses a hospital that does more than five bone marrow transplantations per year.

Treatment by stage

Treatment of breast cancer depends on the type and stage of the disease, and the patient's age, menopausal status, and overall health.

Standard treatment may be considered because of its effectiveness in patients in past studies, or participation in a clinical trial may be considered. Not all patients are cured with standard therapy and some standard treatments may have more side effects than are desired. For these reasons, clinical trials are designed to find better ways to treat cancer patients and are based on the most up-to-date information. Clinical trials are ongoing in most parts of the country for all stages of breast cancer. To learn more about clinical trials,call the Cancer Information Service at 1-800-4-CANCER (1-800-422-6237); TTY at 1-800-332-8615.

Ductal carcinoma in situ

If the patient has ductal carcinoma in situ (DCIS), treatment may be one of the following:
  1. Breast-conserving surgery with radiation therapy, with or without hormone therapy.
  2. Surgery to remove the whole breast (total mastectomy), with or without hormone therapy.
  3. Clinical trials comparing breast-conserving surgery and hormone therapy with or without radiation therapy.

Lobular carcinoma in situ

If the patient has lobular carcinoma in situ (LCIS), treatment may be one of the following:
  1. Biopsy to diagnose the LCIS followed by regular examinations and regular mammograms to find any changes as early as possible.
  2. Hormone therapy to reduce the risk of developing breast cancer.
  3. Clinical trials including a large clinical trial (Study of Tamoxifen and Raloxifene--STAR trial)comparing 2 types of hormone therapy to lower the risk of developing breast cancer and to compare the side effects of treatment. The Cancer Information Service can be called for more information (1-800-4-CANCER).
  4. Surgery to remove all of both breasts (total bilateral mastectomy). This treatment choice is sometimes used in women who have a high risk of getting breast cancer. Most surgeons believe that this is a more aggressive treatment than is needed.

Stage I, ii, and iiia breast cancer

Primary treatment may be one of the following: If the cancer is confined to the breast and lymph nodes under the arm:
  1. Breast-conserving surgery to remove only the cancer and some surrounding breast tissue (lumpectomy) followed by radiation therapy. Some of the lymph nodes under the arm are also removed.
  2. Surgery to remove the whole breast and the lining over the chest muscles (modified radical mastectomy), as well as some of the lymph nodes under the arm with or without breast reconstruction surgery.
  3. A clinical trial evaluating limited lymph node removal (sentinel lymph node biopsy).

Adjuvant therapy (given in addition to the treatments listed above) may include:

  1. Radiation therapy to the lymph nodes under the arm following a modified radical mastectomy.
  2. Systemic chemotherapy with or without hormone therapy.

Stage IIIB, iv, recurrent, and metastatic breast cancer

Treatment for breast cancer that comes back (recurs) to the breast or chest wall may include:
  1. Surgery (radical or modified radical mastectomy) and/or radiation therapy.
  2. Systemic chemotherapy or hormone therapy.

Treatment for Stage IIIB cancer or inflammatory breast cancer may include one or more of the following:

  1. Systemic chemotherapy.
  2. Systemic chemotherapy followed by surgery (breast-conserving surgery or total mastectomy) with lymph node removal followed by radiation therapy. Additional systemic therapy (chemotherapy and/or hormone therapy) may be given).
  3. Clinical trials testing new chemotherapy drugs, new drug combinations, and new ways of giving treatment.

Treatment for Stage IV cancer or metastatic breast cancer may include one or more of the following:

  1. Hormone therapy and/or chemotherapy with or without trastruzumab (Herceptin).
  2. Radiation therapy and/or surgery to relieve the pain caused by the cancer.
  3. Clinical trials testing new chemotherapy and/or hormone therapy. Clinical trials are also studying new combinations of trastruzumab (Herceptin) with chemotherapy drugs.
  4. Clinical trials evaluating other approaches, including high-dose chemotherapy with bone marrow or peripheral stem cell transplantation.



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