About Breast Cancer>Testing > Can a breast cancer diagnosis be wrong?

Can a breast cancer diagnosis be wrong?


It’s unusual but possible for breast cancer tests and even a breast cancer diagnosis to be inaccurate. Before a breast cancer is diagnosed, a person should have several screenings and tests. These may show abnormal results or suspicious tissue that do not always turn out to be breast cancer. It’s also possible for a screening test given alone, without further study, to miss suspicious tissue or other signs you may have breast cancer.

It is less common for a breast cancer diagnosis to be incorrect. No test is perfect. It’s possible that an expert has looked at tissue taken from a biopsy and said you had cancer when you do not, or has said you do not have cancer when you do. In the U.S., we don’t have standards in place to track how often that happens. Different sources believe a very small percentage of U.S. breast cancer diagnoses could be incorrect. Fortunately, there are things you can do to be more certain in your diagnosis and test results.

So how do diagnosis mistakes happen? Here are some examples:

  • If the doctor is not a breast cancer specialist, it’s possible that a symptom could be overlooked that a specialist is more likely to recognize.
  • Clinical errors can sometimes happen when doctors are looking at symptoms and performing a physical exam. One example is inflammatory breast cancer (IBC), which looks different than most breast cancers in that it may not cause a lump; some doctors may not recognize IBC during a clinical exam.
  • Tests can have false-negative and false-positive results:
    • A false-negative result says that there is no cancer present when there actually is cancer present.
    • A false-positive result, on the other hand, appears to be abnormal even though no cancer is present.
  • While no breast cancer test is perfect, a diagnosis is closer to certain once the suspicious tissue is removed from the breast and examined by a pathologist, a doctor who diagnoses diseases by studying cells and tissue under a microscope. Even then, pathology errors can happen. Examples include errors identifying the type of cancer, or whether the cancer has certain features. Still, in many cases, pathologists agree with each other.

If you have concerns about whether your diagnosis is accurate, seeking a second opinion with another doctor can help you better understand and feel more confident about your diagnosis. Learn more about deciding whether you should get a second opinion.

While an abnormal test result can cause feelings of anxiety, if you have an abnormal result, it’s always important to follow up with your doctor for next steps. Don’t wait. If it turns out to be breast cancer, you and your healthcare team may be finding it at an earlier stage, when it’s easier to treat. Or, you could receive confirmation that it’s not actually breast cancer.

Some breast cancers found by screening mammogram turn out not to be life-threatening. But doctors can’t always predict whether a breast cancer is likely to grow or spread away from the breast. Because of this uncertainty, standard practice today is to treat all diagnosed breast cancers. Some experts believe that some of these cancers never needed to be treated and refer to this as overdiagnosis and overtreatment. Overdiagnosis after mammography has been estimated to happen in 1 to 10 percent of cases.

While overdiagnosis remains a challenging issue, the good news is that technology is always improving. Research is also helping doctors define which cancers are life-threatening, and which are not. Advances in medicine are helping doctors to focus more specifically on a person’s unique medical history, genetics, and tumor characteristics to use the most effective screening and treatment plan. This is called precision medicine. Learn more about precision medicine.

Below, you can find more information about the benefits and limitations of common breast cancer diagnostic tests, as well as support resources to help you and your loved ones navigate a breast cancer diagnosis.


Accuracy of breast cancer screening tests

Each breast cancer test has strengths and limitations. This includes the test’s sensitivity and specificity:

  • Sensitivity measures how effectively a test identifies that a person actually has breast cancer.
  • Specificity measures how effectively a test identifies that a person does not have breast cancer.

The closer the test sensitivity and specificity get to 100 percent, the more likely it is that a person does or does not have breast cancer. At the same time, it’s important to know that a highly sensitive test could also bring a false-positive result, because it may pick up things that seem even slightly abnormal. Likewise, a test that is highly specific can overlook tissue that may be cancer and give a false-negative result. The most effective screening tests have both high sensitivity and high specificity.

Below, we’ll walk you through three common screening and diagnostic imaging tests.


Mammograms are x-ray pictures of the breast. They’re the most effective breast cancer screening method available today, looking across the broad groups of people who get screened for breast cancer.

Screening mammograms look for signs of cancer in people with no symptoms. Diagnostic mammograms are used if there are breast symptoms or changes seen on screening mammograms. Diagnostic mammograms can also be used to monitor people who’ve finished breast cancer treatment. It’s important to note that both screening and diagnostic mammograms consist of x-ray pictures of the breast, but they may differ in the types of pictures taken because they have different goals.

Even though mammograms are the best screening tool we have, they’re not perfect, and additional tests are often needed to confirm a diagnosis. It’s possible for mammograms to have false-positive and false-negative results:

  • False-positive mammogram results tend to happen in younger women, women with dense breasts, women who’ve had breast biopsies, and women who have a family history of breast cancer.
  • The likelihood of a false-positive mammogram is highest when you’re having your first mammogram. The odds of having a false-positive drop by about 50 percent once you have past mammograms available for comparison.
  • In women with dense breast tissue, false-negative test results are more likely. Dense breasts are more common in women under age 40, those with a low body mass index, and older women taking combination hormonal replacement therapy.
  • If previous tests have shown that you have dense breast tissue, your doctor may recommend additional testing for you.

Data gathered by the Breast Cancer Surveillance Consortium report screening mammogram sensitivity rates to be as high as 86.9 percent, and specificity rates to be as high as 88.9 percent. However, the sensitivity and specificity of mammography depend on many factors, including how dense the breasts are and how certain tissues are arranged. Some studies show that up to 20 percent of breast cancers cannot be detected on screening mammograms.

Certain types of breast cancer may not easily be found with mammography, such as invasive lobular cancer and inflammatory breast cancer. Diagnosing hard-to-detect breast cancers may require additional testing, such as clinical exam by a breast cancer specialist, ultrasound, MRI, or a nuclear medicine test.

If you’re concerned about radiation from mammograms, it’s important to know that the amount of radiation is small and the exposure is low. The benefits of mammogram for early detection are greater than any potential harm from radiation exposure.

If you receive an abnormal mammogram result, your doctor will talk with you about next steps. This may mean having additional tests to get more information, such as further imaging tests or a needle or surgical biopsy to examine a piece of breast tissue.

Learn more about mammograms.


Breast ultrasounds take pictures of the skin and inside of the breast using sound waves. This test can pick up growths, infections, fluid-filled cysts, and other changes that are often not cancer. These changes aren’t always easy to see on mammograms.

The most common reasons your doctor may recommend an ultrasound include:

  • If a lump can be felt in the breast, but a mammogram doesn’t pick it up
  • To capture more images of a suspicious finding from a mammogram
  • To look for changes in dense breast tissue
  • To tell the difference between solid masses, which may be cancer, and fluid-filled cysts, which are not likely to be cancer

Ultrasound is usually an easy and painless test to have, and it uses no radiation. However, ultrasound does not pick up tiny calcifications, the calcium deposits that, when found in certain patterns, can be signs of breast cancer. Mammograms pick up calcifications more effectively.

False-positive and false-negative results can also happen with ultrasound. In women with dense breasts, more cancers are found when a breast ultrasound is done in addition to mammography, but adding ultrasound to the screening also led to more false-positives. Because of this, it’s not recommended to use ultrasound alone to screen for breast cancer. Instead, it’s often used as a follow-up after mammogram or other tests.

If you receive a positive result after a breast ultrasound, your doctor may recommend a breast biopsy to examine the cells under a microscope and test them directly.

Visit ultrasounds to learn more.


A breast biopsy is a procedure that removes a small amount of tissue from the breast so that it can be studied in the lab. Depending on the situation, biopsies can be minimally invasive or more extensive. Some biopsies can be done with a needle in the doctor’s office. Other situations may require a surgeon making incisions (cuts) to remove the tissue in the operating room.

A biopsy is usually recommended if a mammogram or other tests, or both, show that breast cancer cells may be present. After a biopsy is performed and the tissue is examined, you’ll be given a pathology report that explains what was found. If cancer is found, the report includes information about the features of the cancer. This includes the cancer location, type, stage, hormone-receptor status, and other traits.

While the results of a biopsy are more accurate than results from a mammogram, ultrasound, or other imaging tests, errors can still happen. Pathology errors are not well-tracked in the U.S., but different sources believe a very small percentage of U.S. breast cancer diagnoses could be incorrect.

Visit biopsy and understanding your pathology report pages for more information.


Accepting your diagnosis

If doctors found that you have been accurately diagnosed with breast cancer, you may be experiencing many different emotions. Anger, fear, sadness, or numbness are all common emotional responses to a breast cancer diagnosis.

In our emotional health section, you and the people close to you can find information about processing feelings after a diagnosis, talking with loved ones, and creating an emotional support network. You can also visit the links below:


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Reviewed and updated: May 4, 2021

Reviewed by: Marion Brody, MD


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