The short answer
A mammogram is a low-dose X-ray of the breast used to screen for breast cancer, often finding tumors before they cause symptoms. Results are reported using BI-RADS categories. The USPSTF recommends women at average risk have screening mammograms every 2 years from ages 40 to 74.
A mammogram is a low-dose X-ray of the breast; screening mammograms can find tumors before they cause symptoms.
Mammograms can show masses, calcifications, and breast density; a radiologist looks for unusual changes.
Results are reported using BI-RADS categories (0–6), each with a recommended follow-up.
The USPSTF recommends women at average risk get screening mammograms every 2 years from ages 40 to 74.
Watch: Mammograms: when and how often
49 sec · Captioned · Mammograms every 2 years, ages 40-74 — and why callbacks usually aren't cancer.
Educational only — this video explains general report language and is not medical advice. Only your care team can say what a result means for you.
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The full explanation.
The simple version
A mammogram is an X-ray image of the breast. Screening mammograms look for breast cancer. They can find tumors at an earlier stage, before they cause symptoms. The same machine takes diagnostic mammograms too. Those check a lump or other change after it is found, using images from more angles.
What a mammogram can show
A radiologist studies the images for unusual changes. When possible, they compare them with your past mammograms. Mammograms can show:
- A mass (breast lump). Its size, shape, and edges matter. A smooth, round lump with clear edges is often a benign cyst. A jagged outline or irregular shape may need more tests.
- Calcifications are tiny calcium deposits. They have nothing to do with calcium in your diet. Larger ones (macrocalcifications) are usually benign. Tiny ones grouped together (microcalcifications) can sometimes signal DCIS or breast cancer.
- Breast density is the mix of dense and fatty tissue. Mammography is more likely to miss cancer in dense breasts.
If a symptom is why the mammogram was ordered, that symptom still matters. The deeper guides on breast pain, nipple discharge, and breast lumps can help you frame follow-up questions.
What to expect
Your breast is placed between two plates that press together. That pressure produces a clearer picture. Several images are taken from different angles. The compression can be uncomfortable or briefly painful. An over-the-counter pain reliever beforehand may help. It is best not to book the test right before or during your period. Skip deodorant, powder, lotion, and perfume on the breasts and underarms that day.
How results are reported (BI-RADS)
You'll usually get the radiologist's report within about two weeks. It typically includes a BI-RADS category. That is a standard way of describing findings and the follow-up they call for.
- 0 — More imaging is needed before a category can be given.
- 1 — Negative; continue regular screening.
- 2 — Benign finding; continue regular screening.
- 3 — Probably benign; a 6-month follow-up mammogram.
- 4 — Suspicious; may require a biopsy.
- 5 — Highly suggestive of cancer; requires a biopsy.
- 6 — Known, biopsy-proven cancer.
Being called back for more testing can feel scary. But most people who are called back are not found to have breast cancer.
When to be screened
The U.S. Preventive Services Task Force recommends screening mammograms every 2 years between ages 40 and 74 for women at average risk. Some people are at higher risk. Examples are those with harmful BRCA1 or BRCA2 gene changes, or who had chest radiation for a childhood cancer. They may be advised to begin earlier or screen more often. Your doctor can help you weigh your own personal and family history.
Cost and access
Mammograms are done at breast clinics, hospital radiology departments, mobile vans, and radiology and doctors' offices. You may be able to book a screening mammogram without a referral. Under the Affordable Care Act, screening mammograms are covered as a preventive benefit every 1–2 years for women 40 and over, with no copays. Medicare covers annual screening mammograms for beneficiaries 40 and older. The CDC's National Breast and Cervical Cancer Early Detection Program offers free or low-cost screening for people who are uninsured or low income. NCI's Cancer Information Service (1-800-4-CANCER) can help you find a certified facility.
Words to know
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Common questions
What is a mammogram?
Mammograms are X-ray images of the breasts. They are used for breast cancer screening because they can find tumors at an earlier stage, before they cause symptoms. A mammogram can also be used to check for cancer after a lump or other change is found — this is called a diagnostic mammogram.
What can a mammogram show?
Mammograms can show a mass (breast lump), deposits of calcium called calcifications, breast density, and other changes. A radiologist studies the images for unusual changes and, when possible, compares them with your past mammograms. A smooth, round lump with clear edges is often a benign cyst, while a jagged or irregular shape may need more tests.
What happens during a mammogram?
Your breast is placed between two plates that press together, which helps produce a clearer X-ray. Several images are taken from different angles. The compression can be uncomfortable or briefly painful for some people; an over-the-counter pain reliever beforehand may help. Try not to schedule it right before or during your period, and avoid deodorant, powder, or lotion on the breasts and underarms that day.
What do BI-RADS categories mean?
BI-RADS is a standard way radiologists report mammogram findings, from 0 to 6, each with a recommended follow-up. For example, category 1 is negative and category 2 is a benign finding — both mean continue regular screening; category 0 means more imaging is needed; and categories 4 and 5 (suspicious or highly suggestive of cancer) may require a biopsy. Your results letter explains any follow-up you need.
When should I have a screening mammogram?
The U.S. Preventive Services Task Force recommends that women at average risk have screening mammograms every 2 years between ages 40 and 74. People at higher risk — such as those with harmful BRCA1 or BRCA2 gene changes, or who had chest radiation for a childhood cancer — may be advised to start earlier or screen more often. Talk with your doctor about your personal risk.
What is a 3D mammogram?
Three-dimensional mammography, also called digital breast tomosynthesis (DBT), takes pictures of thin 'slices' across the breast that are assembled into a 3D image. DBT combined with standard mammography is better at finding tumors than standard mammography alone, though it is not yet known whether it reduces deaths from breast cancer more effectively. An NCI-sponsored trial is studying this question.
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Last updated: 2026-08-10Next planned review: 2027-01-03
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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