What does 87% sensitivity actually mean for me?

It means that among 100 women who have breast cancer at the time of screening, the mammogram flags about 87 of them. The other 13 get a normal result and the cancer is found later. Sensitivity describes the test across a population, not your personal odds, which shift with age and breast density.

Is a normal mammogram a guarantee I do not have cancer?

No. The Breast Cancer Surveillance Consortium found about 0.8 cancers per 1,000 screens are present but not seen. A normal result lowers your chance of cancer but does not remove it. Report a new lump, nipple change, or skin change to your doctor even if your last mammogram was clear.

Do false positives mean the radiologist made a mistake?

Usually not. A false positive means the radiologist saw something that needed a closer look, and the extra imaging or biopsy showed no cancer. Recalls are more common on a first mammogram (16.3%) than on later ones (9.6%), because there are no prior images to compare against.

Will insurance cover a breast MRI or ultrasound if my breasts are dense?

Coverage varies by plan and state. The 2024 USPSTF statement found the evidence insufficient to recommend for or against supplemental imaging for dense breasts, so many plans treat it as optional. Ask your imaging center about cost before you schedule, and check whether your state has a supplemental screening coverage law.

Should I switch to annual screening to reduce the chance of a missed cancer?

Annual screening finds some cancers sooner, but it also raises your cumulative false-positive risk from about 42% to about 61% over 10 years. The USPSTF recommends every two years from 40 to 74. Women with dense breasts, a strong family history, or a high risk score may reasonably choose annual screening after talking with their doctor.

How Accurate Are Mammograms, and How Often Do They Miss Cancer?

The short answer: Screening mammography in U.S. community practice has a sensitivity of about 87% and a specificity of about 89%, based on 1.68 million digital exams in the Breast Cancer Surveillance Consortium (BCSC). That means it finds roughly 7 of every 8 cancers present at the time of screening and misses about 1 in 8. Accuracy is much lower in dense breasts: sensitivity falls to about 63% in extremely dense tissue versus 87% in fatty tissue. Over 10 years of annual screening, about 6 in 10 women will get at least one false-positive callback.

How often do mammograms miss cancer?

The best U.S. benchmark comes from the BCSC, a National Cancer Institute-funded network of mammography registries. A 2017 analysis of 1,682,504 digital screening mammograms read by 359 radiologists found:

Sensitivity: 86.9%. The share of cancers present at screening that the mammogram caught.
Specificity: 88.9%. The share of cancer-free women who got a normal result.
Cancer detection rate: 5.1 per 1,000 screens.
False-negative rate: 0.8 per 1,000 screens. Cancers present but not seen.
Recall rate: 11.6%. About 1 in 9 women were called back for more imaging.

The American Cancer Society puts it more simply: screening mammograms miss about 1 in 8 breast cancers. The NCI PDQ summary cites a lower overall sensitivity of about 79% across older and newer studies, and notes sensitivity is worse in younger women and in dense breasts.

A cancer that shows up after a normal screen and before the next scheduled one is called an interval cancer. NCI reports interval cancers at roughly 1 per 1,000 women aged 40 to 49 and 3 per 1,000 women aged 50 to 59. Interval cancers tend to be larger and more aggressive than screen-detected ones, which is why the rate matters.

Why does breast density change the numbers?

Dense breast tissue and cancer both look white on a mammogram. The more dense tissue you have, the easier it is for a tumor to hide. A BCSC study of 463,372 screening mammograms measured this directly. Adjusted sensitivity ranged from 87.0% in almost entirely fatty breasts down to 62.9% in extremely dense breasts. Specificity dropped too, from 96.9% in fatty breasts to 89.1% in extremely dense breasts. Age had a separate effect: sensitivity was 68.6% at ages 40 to 44 and 83.3% at ages 80 to 89.

NCI summarizes the same pattern: for women of all ages, high breast density is associated with 10% to 29% lower sensitivity. The FDA states that about half of U.S. women over 40 have dense breast tissue.

Since September 2024, the FDA's updated Mammography Quality Standards Act rule requires every mammography report to state one of four density categories. The letter you receive must also say whether your tissue is "dense" or "not dense." If it is dense, the letter must tell you that dense tissue makes cancer harder to find and raises breast cancer risk. Our guide to dense breasts walks through the four categories and what each means for you.

Density alone does not decide who needs extra imaging. A BCSC cohort of 831,455 digital screens found that about half of women with dense breasts had low to average 5-year risk. Their interval cancer rate was under 1 per 1,000 exams. High interval cancer rates showed up mainly in women who had dense breasts and an elevated BCSC risk score.

How common are false positives?

A false positive is a callback or biopsy that turns out to be benign. The BCSC tracked 169,456 women who started screening between ages 40 and 59. The results:

False-positive recall probability was 16.3% on a first mammogram and 9.6% on later ones.
False-positive biopsy recommendation was 2.5% on a first exam and 1.0% on later exams.
Over 10 years of annual screening starting at 40, the chance of at least one false-positive recall was 61.3%.
Over 10 years of biennial screening, that chance was 41.6%.
Cumulative false-positive biopsy recommendation was 7.0% with annual and 4.8% with biennial screening.
Having prior mammograms available for comparison halved the odds of a false-positive recall.

The 2024 USPSTF recommendation models a similar burden. Screening every two years from 40 to 74 produces an estimated 1,376 false-positive results per 1,000 women over a lifetime. The same model estimates 14 overdiagnosed cancers per 1,000 women screened. If you get called back, read our callback guide before you panic. About 9 in 10 callbacks end without a cancer diagnosis.

Does 3D mammography find more cancer?

Digital breast tomosynthesis (DBT, or 3D mammography) takes a series of thin image slices instead of one flat picture. The largest early U.S. study, published in JAMA in 2014, compared 454,850 exams at 13 centers before and after they added DBT. Adding tomosynthesis:

Cut the recall rate from 107 to 91 per 1,000 screens.
Raised the cancer detection rate from 4.2 to 5.4 per 1,000 screens.
Raised invasive cancer detection from 2.9 to 4.1 per 1,000 screens.

A 2023 BCSC follow-up looked at what happens over several rounds. In 523,485 DBT and 1,008,123 2D exams, DBT had a lower recall rate at every round. The advantage was largest on round one (3.3 percentage points lower) and shrank to 1.2 points by round three. DBT found more cancers only at round three and beyond (0.6 more per 1,000 exams). Interval cancer rates and advanced cancer rates were the same for both methods. The USPSTF reached a similar conclusion: both 2D and DBT are effective screening tools, with no significant difference in detection across two rounds. For a fuller comparison, see 3D vs 2D mammograms.

When does ultrasound or MRI make sense?

Supplemental screening adds a second test after a normal mammogram. The strongest evidence is for breast MRI in extremely dense breasts. The Dutch DENSE trial randomized 40,373 women aged 50 to 75 with extremely dense breasts and a normal mammogram. Women invited to MRI had 2.5 interval cancers per 1,000 screens, versus 5.0 per 1,000 with mammography alone. Among women who actually had the MRI, the interval cancer rate was 0.8 per 1,000. MRI detected 16.5 additional cancers per 1,000 screens. The cost was a false-positive rate of 79.8 per 1,000 MRI screens.

Guidelines differ on what to do with that evidence. The USPSTF says current evidence is insufficient to judge the benefits and harms of supplemental ultrasound or MRI for dense breasts alone. The American College of Radiology recommends annual supplemental MRI for women at higher-than-average risk, including those with a personal history of breast cancer and dense breasts. It also recommends a formal risk assessment for all women by age 25. If you want to understand what a breast MRI involves and how it differs from mammography, mri.md covers the exam in detail.

What can you do to improve your odds?

Know your density category. Your report letter now states it. If it says "dense," ask your doctor whether your overall risk justifies added imaging.
Get a risk estimate. The BCSC data show that density plus a 5-year risk score predicts interval cancer better than density alone.
Bring prior images. Comparison with earlier mammograms cut false-positive recalls in half in the BCSC cohort.
Ask about 3D. DBT lowers callbacks, especially on a first exam.
Report symptoms between screens. A normal mammogram does not cover a new lump, nipple discharge, skin dimpling, or a change in breast shape. These need a diagnostic workup regardless of your last screening date.
Keep the schedule. A missed cancer is far more likely if you skip screening than if you screen on time.

The bottom line

Mammography is a good test, not a perfect one. In U.S. practice it catches about 87% of cancers present at screening and misses about 1 in 8. In extremely dense breasts, that miss rate roughly triples. False positives are common: about 61% of women screened annually for 10 years will get at least one callback. 3D mammography lowers callbacks and finds a few more cancers. Supplemental MRI halves interval cancers in extremely dense breasts but adds false positives. Know your density, keep prior images, and report symptoms between screens.

Last updated: September 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your doctor or radiologist about your breast density, your personal risk, and whether supplemental screening is right for you.