Breast Cancer

Introduction to Breast Cancer

According to the National Cancer Institute, 1 in 50 women will develop breast cancer by age 50 and 1 in 10 women will develop breast cancer by age 80. Breast cancer is the most commonly diagnosed cancer in women second only to skin cancer. Every year, more than 180,000 women are diagnosed with breast cancer and 45,000 women die from it. Breast cancer has been seen to occur more often in white women than African American or Asian women. Breast cancer has also been seen in men, but it makes up less than 1% of all breast cancer cases.

What Is Breast Cancer and How is it Diagnosed?

Breast cancer is a disease in which the breast cells grow and reproduce themselves abnormally. It can present as a lump, a thickening, or a skin change. Breast cancer is diagnosed histologically, which means that specific breast tissue changes have to be seen before the diagnosis is confirmed. When a tumor is analyzed, it is further defined by classifying it into stages. Breast cancer staging is used to provide an estimate of disease-free survival, overall survival, and the risk of cancer recurrence. It is also used to determine the course of therapy. A patient with a low-stage tumor has a greater chance of surviving breast cancer than a patient with a high-stage tumor, according to findings from the National Cancer Institute. (Staging is described further in Breast Cancer Staging.)

What Are Factors That Can Contribute to Breast Cancer?

Both genetic and non-genetic factors contribute to the risk of breast cancer.

What are the non-genetic factors?
The following factors may minimally increase the risk for breast cancer:

  • Hormonal history, which includes:
    • Menarche before the age of 12,
    • Menopause after age 55 years,
    • First child born after the maternal age of 30 years,
    • Nulliparity (never having given birth).

    Further discussion of the effects of estrogen on breast and ovarian cancer risk can be found in the section The Role of Estrogen in Breast and Ovarian Cancer.

    • Excessive radiation exposure
    • Obesity
    • Alcohol use
    • Atypical hyperplasia of breast tissue: Atypical hyperplasia is the presence of excessive growth of abnormal cells. Although these cells are not cancerous, a woman with atypical hyperplasia has a 2 to 4 times greater risk of developing breast cancer over her lifetime. Atypical hyperplasia is diagnosed by biopsy and has been found to occur in approximately 5% of all breast biopsies.
    • Other risk factors have been suggested, but not proven, to increase the risk for breast cancer. One example is a diet high in fat and low in fiber, fruits, and vegetables combined with a lack of exercise.

    What are genetic factors that can contribute to breast cancer?
    Extensive research has indicated that hereditary (also known as familial) cases of breast and ovarian cancer are caused by genetic factors that are influenced by a common environment. Thus, both genes and environment play a role.

    Women with a familial form of breast cancer were typically found to have:

    • A personal history of breast cancer diagnosed before 50 years of age, especially with bilateral breast cancer or multiple primary tumors in the same breast
    • More than one relative with breast cancer diagnosed before 45 to 50 years
    • One or more relatives affected with bilateral or multifocal breast cancer
    • Positive family history of ovarian or male breast cancer

    Genetic factors that can contribute to breast cancer are:

  • Predisposition genes: These are genes which, when damaged or mutated, lead to a higher likelihood of developing a disease. These genes may account for 5 to 10% of all cases of breast cancer. At this time, research has found two predispositional genes specifically for breast cancer, called BRCA1 and BRCA2 (BReast CAncer 1 and 2). Women with mutations in either of these two genes are more likely to develop breast cancer but are not guaranteed to do so. As research progresses, more genes may be discovered that are related to familial forms of breast cancer. For a more in-depth discussion of this topic, see Jewish Genetics and Breast/Ovarian Cancer, and Possibilities for BRCA3.
  • Certain genetic syndromes: Several genetic syndromes can result in breast cancer and other clinical manifestations. They are believed to account for less than 1% of all breast cancer cases. Some of these genetic syndromes are Li-Fraumeni syndrome, Ataxia-Telangiectasia, Bloom syndrome, Peutz-Jeghers syndrome, Cowdens syndrome, HNPCC (Hereditary Non-Polyposis Colorectal Cancer), and Xeroderma Pigmentosa. Bloom Syndrome and HNPCC are covered in other sections. The other syndromes are not discussed further on this website because they are not associated with Jewish genetic disorders.
  • Common variations in genes: Recent research has been exploring the concept that some commonly occurring genetic variants might be low risk factors for certain types of cancer. The theory is that these factors may be much more common in the general population than high risk mutations, such as BRCA1 and BRCA2, and may have a larger effect on overall population risk. More information on these variations can be found in Common Genetic Variants and Breast Cancer Risk.

    What Can I do to Monitor for Breast Cancer?

    For women at all levels of risk to develop breast cancer, only mammography has been shown to be helpful in detecting breast cancer when it is still at an early stage. However, the following recommendations have been made for other forms of surveillance to encourage early detection:

    • Yearly clinical breast exam beginning at the age of 25 to 35 years.
    • Yearly mammograms beginning between the age of 40 and 50 years. For women known to be at high risk, yearly mammograms are recommended starting at the age of 25 to 35 years.

    Please note that the only monitoring technique that has been proven to be beneficial for individuals with a genetic susceptibility to breast or ovarian cancer is routine mammography screening. Yearly mammograms are recommended to women of average risk beginning at the age of 40 to 50 years. At this time, additional experimental approaches to surveillance of breast cancer are currently being evaluated, but to date are unproven to be helpful.

    What Happens When Breast Cancer Has Been Diagnosed?

    Once breast cancer has been diagnosed, five major types of treatment are commonly used. The therapy or combination of therapies that is undertaken depends upon the location, size, and staging of the tumor and the overall health of the patient.

    The different treatments are:

    • Surgery: Surgery is used to remove existing tumors. It may also be done prophylactically to remove tissue that is at high risk to become cancerous.
    • Radiation: This treatment consists of large doses of high-energy beams or particles that destroy cancer cells in a specifically targeted area.
    • Hormonal therapy: Hormonal therapy is used to block hormones (occurring naturally in the body) that are involved in stimulating the growth of cancerous cells. Examples of this type of therapy are anti-estrogen drugs. Sometimes, surgery is necessary to remove the source of the body’s naturally occurring hormone. For example, female hormones are produced by the ovaries, and their surgical removal (called an oophorectomy) blocks this production. (Estrogen is covered in more depth in The Role of Estrogen and Breast and Ovarian Cancer.)
    • Chemotherapy: This therapy involves the use of anticancer drugs that kill cancer cells and/or control their growth. When these drugs are administered, they enter the bloodstream and travel throughout the body. Chemotherapy is often used when metastasis has occurred.
    • Biotherapy: This treatment involves administering drugs which stimulate the body’s own defense system (immune system) to fight cancer by blocking the growth of cancer cells.


    Reviewed by Wendy Rubinstein, MD, PhD, Center for Medical Genetics, Evanston Northwestern Healthcare 8/03.