Topic updated: September 2011

Breast Cancer

The Breasts

Inside a woman's breast are 15 to 20 sections called lobes. Each lobe is made of many smaller sections called lobules. Lobules have groups of tiny glands that can make milk. After a baby is born, a woman's breast milk flows from the lobules through thin tubes called ducts to the nipple. Fat and fibrous tissue fill the spaces between the lobules and ducts.

The breasts also contain lymph vessels. These vessels are connected to small, round masses of tissue called lymph nodes. Groups of lymph nodes are near the breast in the underarm (axilla), above the collarbone, and in the chest behind the breastbone.

Cancer cells

Cancer begins in cells, the building blocks that make up tissues. Tissues make up the breasts and other parts of the body.

Normal cells grow and divide to form new cells as the body needs them. When normal cells grow old or get damaged, they die, and new cells take their place.

Sometimes, this process goes wrong. New cells form when the body doesn't need them, and old or damaged cells don't die as they should. The buildup of extra cells often forms a mass of tissue called a lump, growth, or tumor.

Tumors in the breast can be benign (not cancer) or malignant (cancer). Benign tumors are not as harmful as malignant tumors:

Benign tumors:

  • are rarely a threat to life
  • can be removed and usually don't grow back
  • don't invade the tissues around them
  • don't spread to other parts of the body

Malignant tumors:

  • may be a threat to life
  • often can be removed but sometimes grow back
  • can invade and damage nearby organs and tissues (such as the chest wall)
  • can spread to other parts of the body

Breast cancer cells can spread by breaking away from the original tumor. They enter blood vessels or lymph vessels, which branch into all the tissues of the body. The cancer cells may be found in lymph nodes near the breast. The cancer cells may attach to other tissues and grow to form new tumors that may damage those tissues.

The spread of cancer is called metastasis.

Risk Factors

When you're told that you have breast cancer, it's natural to wonder what may have caused the disease. But no one knows the exact causes of breast cancer. Doctors seldom know why one woman develops breast cancer and another doesn't.

Doctors do know that bumping, bruising, or touching the breast does not cause cancer. And breast cancer is not contagious. You can't catch it from another person.

Doctors also know that women with certain risk factors are more likely than others to develop breast cancer. A risk factor is something that may increase the chance of getting a disease.

Some risk factors (such as drinking alcohol) can be avoided. But most risk factors (such as having a family history of breast cancer) can't be avoided.

Studies have found the following risk factors for breast cancer:

  • Age: The chance of getting breast cancer increases as you get older. Most women are over 60 years old when they are diagnosed.

  • Personal health history: Having breast cancer in one breast increases your risk of getting cancer in your other breast. Also, having certain types of abnormal breast cells (atypical hyperplasia, lobular carcinoma in situ [LCIS], or ductal carcinoma in situ [DCIS]) increases the risk of invasive breast cancer. These conditions are found with a breast biopsy.

  • Family health history: Your risk of breast cancer is higher if your mother, father, sister, or daughter had breast cancer. The risk is even higher if your family member had breast cancer before age 50. Having other relatives (in either your mother's or father's family) with breast cancer or ovarian cancer may also increase your risk.

  • Certain genome changes: Changes in certain genes, such as BRCA1 or BRCA2, substantially increase the risk of breast cancer. Tests can sometimes show the presence of these rare, specific gene changes in families with many women who have had breast cancer, and health care providers may suggest ways to try to reduce the risk of breast cancer or to improve the detection of this disease in women who have these genetic changes.

    Also, researchers have found specific regions on certain chromosomes that are linked to the risk of breast cancer. If a woman has a genetic change in one or more of these regions, the risk of breast cancer may be slightly increased. The risk increases with the number of genetic changes that are found. Although these genetic changes are more common among women than BRCA1 or BRCA2, the risk of breast cancer is far lower.

  • Radiation therapy to the chest: Women who had radiation therapy to the chest (including the breasts) before age 30 are at an increased risk of breast cancer. This includes women treated with radiation for Hodgkin lymphoma. Studies show that the younger a woman was when she received radiation treatment, the higher her risk of breast cancer later in life.

  • Reproductive and menstrual history:

    • The older a woman is when she has her first child, the greater her chance of breast cancer.

    • Women who never had children are at an increased risk of breast cancer.

    • Women who had their first menstrual period before age 12 are at an increased risk of breast cancer.

    • Women who went through menopause after age 55 are at an increased risk of breast cancer.

    • Women who take menopausal hormone therapy for many years have an increased risk of breast cancer.

  • Race: In the United States, breast cancer is diagnosed more often in white women than in African American/black, Hispanic/Latina, Asian/Pacific Islander, or American Indian/Alaska Native women.

  • Breast density: Breasts appear on a mammogram (breast x-ray) as having areas of dense and fatty (not dense) tissue. Women whose mammograms show a larger area of dense tissue than the mammograms of women of the same age are at increased risk of breast cancer.

  • History of taking DES: DES was given to some pregnant women in the United States between about 1940 and 1971. (It is no longer given to pregnant women.) Women who took DES during pregnancy may have a slightly increased risk of breast cancer. The possible effects on their daughters are under study.

  • Being overweight or obese after menopause: The chance of getting breast cancer after menopause is higher in women who are overweight or obese.

  • Lack of physical activity: Women who are physically inactive throughout life may have an increased risk of breast cancer.

  • Drinking alcohol: Studies suggest that the more alcohol a woman drinks, the greater her risk of breast cancer.

Having a risk factor does not mean that a woman will get breast cancer. Most women who have risk factors never develop breast cancer.

Many other possible risk factors have been studied. For example, researchers are studying whether women who have a diet high in fat or who are exposed to certain substances in the environment have an increased risk of breast cancer. Researchers continue to study these and other possible risk factors.

Symptoms

Early breast cancer usually doesn't cause symptoms. But as the tumor grows, it can change how the breast looks or feels. The common changes include:

  • A lump or thickening in or near the breast or in the underarm area
  • A change in the size or shape of the breast
  • Dimpling or puckering in the skin of the breast
  • A nipple turned inward into the breast
  • Discharge (fluid) from the nipple, especially if it's bloody
  • Scaly, red, or swollen skin on the breast, nipple, or areola (the dark area of skin at the center of the breast). The skin may have ridges or pitting so that it looks like the skin of an orange.

You should see your health care provider about any symptom that does not go away. Most often, these symptoms are not due to cancer. Another health problem could cause them. If you have any of these symptoms, you should tell your health care provider so that the problems can be diagnosed and treated.

Detection and Diagnosis

Your doctor can check for breast cancer before you have any symptoms. During an office visit, your doctor will ask about your personal and family medical history. You'll have a physical exam. Your doctor may order one or more imaging tests, such as a mammogram.

Doctors recommend that women have regular clinical breast exams and mammograms to find breast cancer early. Treatment is more likely to work well when breast cancer is detected early.

You may want to read the NCI booklet Understanding Breast Changes. It describes types of breast changes and tests used to find changes.

Clinical Breast Exam

During a clinical breast exam, your health care provider checks your breasts. You may be asked to raise your arms over your head, let them hang by your sides, or press your hands against your hips. Your health care provider looks for differences in size or shape between your breasts. The skin of your breasts is checked for a rash, dimpling, or other abnormal signs. Your nipples may be squeezed to check for fluid.

Using the pads of the fingers to feel for lumps, your health care provider checks your entire breast, underarm, and collarbone area. A lump is generally the size of a pea before anyone can feel it. The exam is done on one side and then the other. Your health care provider checks the lymph nodes near the breast to see if they are enlarged.

If you have a lump, your health care provider will feel its size, shape, and texture. Your health care provider will also check to see if the lump moves easily. Benign lumps often feel different from cancerous ones. Lumps that are soft, smooth, round, and movable are likely to be benign. A hard, oddly shaped lump that feels firmly attached within the breast is more likely to be cancer, but further tests are needed to diagnose the problem.

Mammogram

A mammogram is an x-ray picture of tissues inside the breast. Mammograms can often show a breast lump before it can be felt. They also can show a cluster of tiny specks of calcium. These specks are called microcalcifications. Lumps or specks can be from cancer, precancerous cells, or other conditions. Further tests are needed to find out if abnormal cells are present.

Before they have symptoms, women should get regular screening mammograms to detect breast cancer early:

  • Women in their 40s and older should have mammograms every 1 or 2 years.
  • Women who are younger than 40 and have risk factors for breast cancer should ask their health care provider whether to have mammograms and how often to have them.

If the mammogram shows an abnormal area of the breast, your doctor may order clearer, more detailed images of that area. Doctors use diagnostic mammograms to learn more about unusual breast changes, such as a lump, pain, thickening, nipple discharge, or change in breast size or shape. Diagnostic mammograms may focus on a specific area of the breast. They may involve special techniques and more views than screening mammograms.

To learn more about mammograms, you may want to read the NCI fact sheet Mammograms.

Other Imaging Tests

If an abnormal area is found during a clinical breast exam or with a mammogram, the doctor may order other imaging tests:

  • Ultrasound: A woman with a lump or other breast change may have an ultrasound test. An ultrasound device sends out sound waves that people can't hear. The sound waves bounce off breast tissues. A computer uses the echoes to create a picture. The picture may show whether a lump is solid, filled with fluid (a cyst), or a mixture of both. Cysts usually are not cancer. But a solid lump may be cancer.
  • MRI: MRI uses a powerful magnet linked to a computer. It makes detailed pictures of breast tissue. These pictures can show the difference between normal and diseased tissue.

Biopsy

A biopsy is the removal of tissue to look for cancer cells. A biopsy is the only way to tell for sure if cancer is present.

You may need to have a biopsy if an abnormal area is found. An abnormal area may be felt during a clinical breast exam but not seen on a mammogram. Or an abnormal area could be seen on a mammogram but not be felt during a clinical breast exam. In this case, doctors can use imaging procedures (such as a mammogram, an ultrasound, or MRI) to help see the area and remove tissue.

Your doctor may refer you to a surgeon or breast disease specialist for a biopsy. The surgeon or doctor will remove fluid or tissue from your breast in one of several ways:

  • Fine-needle aspiration biopsy: Your doctor uses a thin needle to remove cells or fluid from a breast lump.
  • Core biopsy: Your doctor uses a wide needle to remove a sample of breast tissue.
  • Skin biopsy: If there are skin changes on your breast, your doctor may take a small sample of skin.
  • Surgical biopsy: Your surgeon removes a sample of tissue.
    • An incisional biopsy takes a part of the lump or abnormal area.
    • An excisional biopsy takes the entire lump or abnormal area.

A pathologist will check the tissue or fluid removed from your breast for cancer cells. If cancer cells are found, the pathologist can tell what kind of cancer it is. The most common type of breast cancer is ductal carcinoma. It begins in the cells that line the breast ducts. Lobular carcinoma is another type. It begins in the lobules of the breast.

Lab Tests with Breast Tissue

If you are diagnosed with breast cancer, your doctor may order special lab tests on the breast tissue that was removed:

  • Hormone receptor tests: Some breast tumors need hormones to grow. These tumors have receptors for the hormones estrogen, progesterone, or both. If the hormone receptor tests show that the breast tumor has these receptors, then hormone therapy is most often recommended as a treatment option.
  • HER2/neu test: HER2/neu protein is found on some types of cancer cells. This test shows whether the tissue either has too much HER2/neu protein or too many copies of its gene. If the breast tumor has too much HER2/neu, then targeted therapy may be a treatment option.

It may take several weeks to get the results of these tests. The test results help your doctor decide which cancer treatments may be options for you.

Read the rest of this great article, including staging and treatment information, from the National Cancer Institute.

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