Breast Cancer Diagnosis and Screening

American Family Physician,  August 1, 2000  by Lecia M. Apantaku

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Approximately 180,000 new cases of breast cancer are diagnosed annually, accounting for about 48,000 deaths per year in the United States. The screening guidelines for the diagnosis of breast cancer are continually changing. Because of increased awareness of the signs and symptoms of breast cancer and the use of screening mammograms, breast cancers are increasingly being diagnosed at earlier stages. Annual mammograms and clinical breast examinations are recommended for women older than 40 years. Women older than 20 years should be encouraged to do monthly breast self-examinations, and women between 20 and 39 years of age should have a clinical breast examination every three years. These guidelines are modified for women with risk factors, particularly those with a strong family history of breast cancer. Ultrasonographic studies are most useful to evaluate cystic breast masses. For solid masses, diagnostic biopsy techniques include fine-needle aspiration, core biopsy and excisional biopsy. (Am Fam Physician 2000;62:596-602,605-6.)

Members of various family practice departments develop articles for "Problem-Oriented Diagnosis." This article is one in a collaborative series coordinated by David R. Rudy, M.D., M.P.H., from the Department of Family Medicine at the Chicago Medical School of Finch University of Health Sciences, and Martin Lipsky, M.D., from the Department of Family Medicine at Northwestern University Medical School, Chicago.

Breast cancer is the second most commonly diagnosed cancer among women, after skin cancer.(1) Approximately 182,800 new cases of invasive breast cancer will be diagnosed among women in the United States during 2000.(1) After increasing about 4 percent per year during the 1980s, breast cancer rates leveled off in the 1990s to about 110 cases per 100,000 per year.(1) Breast cancer is the second leading cause of cancer death in women, after lung cancer. Approximately 48,800 American women are expected to die of breast cancer in 2000.(1)

Demographics

The incidence of breast cancer increases with age (Table 1).(2) White women are more likely to develop breast cancer than black women. The incidence of breast cancer in white women in 1993 was about 113 cases per 100,000 women and in black women, 100 cases per 100,000.2 However, black women younger than 50 years have a higher incidence of breast cancer than white women. In 1993, black women were more likely to die of breast cancer than white women.(2) Although breast cancer usually is associated with women, 1 percent of breast cancers occur in men. Men should be aware of the relevant risk factors, including family history, and be encouraged to report any changes in their breasts to a physician.

Risk Factors

Several well-established risk factors (Table 2) are associated with the development of breast cancer,(3) primarily age and female sex.(4) Family history is highly significant in a first-degree relative (i.e., mother, sister, daughter) especially if the cancer has been diagnosed premenopausally.(3) Women who have premenopausal first-degree relatives with breast cancer have a three- to fourfold increased risk of developing breast cancer than women who do not. Having several second-degree relatives with breast cancer may further increase the risk of developing breast cancer, but this risk has not been quantified. It is important to note that most women with breast cancer have no identifiable risk factors.

Approximately 8 percent of all cases of breast cancer are hereditary. About one half of these cases are attributed to mutations in two breast cancer susceptibility genes, BRCA1 and BRCA2.(5) Hereditary breast cancer commonly occurs in premenopausal women and is more frequently bilateral than nonhereditary breast cancer.(5) Several family members are affected over three generations or more and can include women from the paternal side of the family. Screening tests are available that detect BRCA mutations.

Genetic testing is controversial and raises issues about the reliability of tests and the use made of test results. A woman who tests positive may worry about job or insurance discrimination. She may consider possible prophylactic mastectomy and oophorectomy. A woman who tests negative for a particular mutation may still be at risk for developing breast cancer from a sporadic mutation or a preexisting unidentified mutation. A false-negative test is also possible. Genetic counseling before being tested is highly recommended, and patients are required to sign a consent form.

Obtaining a history of previous breast biopsy is essential because a history of a proliferative abnormality such as atypical hyperplasia on biopsy may increase a woman's risk for developing breast cancer. A history of breast cancer increases the risk of developing a new breast cancer by 0.5 to 1.0 percent per year.(2) Because conservative treatments are increasingly common in women with first breast cancers, many second cancers now appear in the same breast.