What are the limitations of mammography and why is it important for women know about them?

Mammography is the best test we have at this time to find breast cancer early, but it has known limitations -- it will find most, but not all, breast cancers. The American Cancer Society supports informing women about the limitations of mammography so they will have reasonable expectations about its accuracy and usefulness. Studies show that informing women of the limitations of mammography before they have one decreases anxiety and improves later adherence with screening recommendations.

The accuracy of mammography improves as women age – thus, accuracy is slightly better for women in their 50s than women in their 40s and slightly better for women in their 60s than women in their 50s, and so on. However, a woman undergoing breast cancer screening needs to know that mammography at any age is not 100% accurate. Overall, mammography will detect about 85% of breast cancers.

Women also need to be prepared for the possibility of being called back for additional testing, even though most women who get further testing do not have breast cancer. On average, about 10% of women are recalled for further evaluation, including additional mammography and/or ultrasound, and sometimes a biopsy to determine if cancer is present.

Women also need to know that if their mammogram result is normal, but they detect a symptom months later before their next mammogram, they should see a doctor right away.