Understanding results: what the BI-RADS categories mean

A breast screening result often arrives as a short letter, often with a single number. This page explains how the numbered BI-RADS categories work, what being called back means, and which tests can follow. It describes the system in general and cannot say what any one person's result means. Screening policy differs between countries and between people, and your own doctor or screening service has the final word.

What a screening report or letter can contain

After a mammogram, a low-dose x-ray picture of the breast, a radiologist (a doctor who interprets imaging tests) reads the images. In the United States, the National Cancer Institute says the report usually includes the BI-RADS category and a note on breast density, and that screening results reach you within about 2 weeks by mail or in an electronic record.11National Cancer Institute: Mammograms Describes the report, the BI-RADS table and the usual 2 week wait for screening results in the US; page opened 11 October 2026. The NHS describes a similar pattern in England, with a letter usually within 2 weeks and a copy to the person's GP.22NHS: Your breast screening results Page last reviewed 9 October 2025; results usually within 2 weeks, sent by letter.

A full radiology report is written for your healthcare provider and may contain unfamiliar terms. RadiologyInfo.org suggests marking what you do not understand and writing down questions, and notes you should also receive a letter in an easier format.33RadiologyInfo.org: How to Read Your Breast Imaging Report using BI-RADS Last reviewed 9 September 2024; explains the sections of a breast imaging report.

The BI-RADS categories, 0 to 6

BI-RADS stands for Breast Imaging Reporting and Data System. Doctors use it so everyone describes mammogram findings in the same words, which makes sharing results and arranging follow-up easier. The same categories are also used for breast ultrasound and breast MRI, although recommended next steps after those tests can differ slightly.44American Cancer Society: Understanding Your Mammogram Report Last revised 23 July 2026; source of the category names and percentages in the table below.

1. 0Incomplete
2. 1Negative
3. 2Benign
4. 3Probably benign
5. 4Suspicious
6. 5Highly suggestive of malignancy
7. 6Known biopsy-proven malignancy

A BI-RADS number is not a diagnosis. RadiologyInfo.org describes it as a way for the radiologist to pass impressions and recommended next steps to your doctor, and says a report can carry more than one number because different findings may be rated differently.33RadiologyInfo.org: How to Read Your Breast Imaging Report using BI-RADS States that a BI-RADS score is not a diagnosis and that a report may include more than one number. A biopsy, in which a small tissue sample is examined under a microscope, is what provides a diagnosis.

Breast density in a letter

Reports also describe breast density, meaning how much fibrous and glandular tissue the breasts contain compared with fat. The American Cancer Society notes that denser breasts make abnormal areas harder to see on a mammogram, and that BI-RADS sorts density into four groups labeled A to D.44American Cancer Society: Understanding Your Mammogram Report Describes density and the four BI-RADS density groups. What a density note means for later steps is covered on the page about dense breasts and screening.

What a recall, or callback, means

A recall is a request to return for more imaging after a screening test. The American Cancer Society calls it fairly common, says it does not mean you have breast cancer, and states that fewer than 1 in 10 women called back for more tests are found to have cancer.55American Cancer Society: Getting Called Back After a Mammogram Source of the fewer than 1 in 10 figure, which refers to women called back after a screening mammogram. The NHS likewise says most people who need further tests will not be diagnosed with breast cancer.22NHS: Your breast screening results Reviewed 9 October 2025; most people who need further tests are not diagnosed with breast cancer. These figures describe groups of people, not any one person.

RadiologyInfo.org puts the share of screening mammograms needing more testing at 5% to 15%, and says most of those tests turn out to be normal.66RadiologyInfo.org: Mammography Last reviewed 4 February 2025; gives the 5% to 15% range for screening mammograms needing more testing. Recalls are more common after a first mammogram, when there are no earlier images to compare, before menopause, and with denser tissue.55American Cancer Society: Getting Called Back After a Mammogram Lists situations in which a callback is more common. The trade-off between extra tests and early detection is covered on the page about benefits and harms of screening.

Tests that can follow a recall

The next step depends on the reason for the recall. The NHS lists an examination of the breast, more mammograms, ultrasound scans and a needle biopsy.22NHS: Your breast screening results Lists the further tests that may be offered after a screening result. A diagnostic mammogram is done like the first one but with more pictures, so an abnormal area can be studied closely, and ultrasound uses sound waves to picture areas inside the breast.55American Cancer Society: Getting Called Back After a Mammogram Describes diagnostic mammograms, ultrasound and the recall visit. The methods of breast cancer screening page compares these tests.

If a biopsy is advised, the American Cancer Society says most biopsy results are not cancer, though a biopsy is the only way to know for sure.55American Cancer Society: Getting Called Back After a Mammogram States that most biopsy results are not cancer and that biopsy is the only sure test. The same page says worry is normal in this period and that talking with a loved one, a counselor or others who have been called back may help.

Questions to bring to the next appointment

Useful questions: which category was assigned, what follow-up is recommended, and whom to call. RadiologyInfo.org advises asking when results will be available and not assuming they are normal if you hear nothing.66RadiologyInfo.org: Mammography Advises asking when results will be available and not assuming they are normal if you do not hear. The National Cancer Institute advises contacting your provider if results have not arrived within 2 weeks.11National Cancer Institute: Mammograms Advises contacting your provider if screening results have not arrived within 2 weeks. For earlier steps see preparing for a screening appointment, or return to the main guide. Guidance can change, so check the current advice of your own screening service.