Your test results may be positive, negative or uncertain.

Positive test result

A positive test result means that you have a mutation in one of the breast cancer genes, BRCA1 or BRCA2, and therefore a much higher risk of developing breast cancer or ovarian cancer compared with someone who doesn't have the mutation. But a positive result doesn't mean that you'll ultimately develop cancer.

Follow-up care after a positive test result might include taking specific measures to modify the type and frequency of screening for cancer and to consider procedures and medications designed to reduce your cancer risk. What you choose to do depends on many factors — including your age, medical history, prior treatments, past surgeries and personal preferences.

Your options might include:

  • Increased screening (surveillance). Surveillance for breast cancer if you have a BRCA mutation means having clinical breast exams every six months and mammograms and magnetic resonance imaging (MRI) exams every year. Some experts recommend alternating mammogram and breast MRI every six months. These tests don't prevent breast cancer but may help detect it early. Substituting mammography plus MRI screening for prophylactic mastectomy can offer comparable survival.

    You may also choose to perform monthly breast self-exams to become familiar with the normal texture of your breast tissue. Potentially worrisome breast changes may be easier for you to detect earlier if you know what's normal.

    Surveillance for ovarian cancer with available tests has not been found to be effective in early detection of cancer, nor has it shown a survival benefit. The tests include having semiannual pelvic exams and yearly transvaginal ultrasound imaging and a blood test to measure your cancer antigen 125 level.

  • Oral contraceptives. Oral contraceptive use has been shown to reduce ovarian cancer risk in BRCA mutation carriers. Your risk of breast cancer goes up slightly if you use oral contraceptives for more than five years, however.
  • Medication to reduce your risk of cancer (chemoprevention). Tamoxifen reduces the risk of developing breast cancer by about 50 percent in women who are at increased risk of the disease. Some small studies have shown that tamoxifen may help lower the risk in women specifically with a BRCA2 gene mutation.

    Other preventive medications include raloxifene (Evista), exemestane (Aromasin) and anastrozole (Arimidex), which also help reduce the chance of breast cancer in postmenopausal women at high risk, though they haven't been studied specifically in women with BRCA mutations.

  • Preventive surgery. Preventive (prophylactic) mastectomy — surgical removal of healthy breast tissue — reduces breast cancer risk for BRCA gene carriers by about 90 percent, according to several studies. Removal of healthy fallopian tubes and ovaries (preventive salpingo-oophorectomy) reduces breast cancer risk by as much as 50 percent in premenopausal women, and it reduces ovarian cancer risk in both pre- and postmenopausal women.

    Preventive surgery doesn't eliminate all cancer risk. It's possible for cancer to develop in any tissue that couldn't be removed through surgery.

Negative or uncertain test result

A negative test result means that no BRCA gene mutation was found. However, assessing your cancer risk is still difficult. The test result is considered a "true negative" only if it finds that you don't carry a specific BRCA mutation that's already been identified in a relative.

An ambiguous result, also known as a variant of uncertain significance, occurs when the analysis finds a genetic variant that may or may not be associated with an increased risk of cancer. It is helpful to meet with your genetic counselor to understand how to interpret this finding and decide on appropriate follow-up.

New models are being developed to help determine risk of cancer with ambiguous results. Most variants of uncertain significance are eventually reclassified into either a positive or negative result. To be informed when this happens, stay in touch with the doctor or genetic counselor who ordered your genetic test.

Keep in mind that a negative test result doesn't eliminate the chance of developing a nonhereditary breast cancer. You still have the same cancer risk as that of the general population.

Although the BRCA gene test can detect the majority of mutations in the BRCA1 and BRCA2 genes, you could have a gene mutation that the test wasn't able to detect. Or you may be at high risk of hereditary cancer if your family carries a high-risk gene mutation that researchers haven't yet identified. Finally, your family may have another hereditary cancer gene mutation that can be detected with other genetic tests.