BI-RADS
Meaning of BI-RADS: A shared vocabulary and a numbered ending for breast imaging reports, built so the same words mean the same thing everywhere.
Definition of BI-RADS
BI-RADS is a standardized system for describing and reporting breast imaging, covering mammograms, ultrasound and MRI scans. It supplies a fixed vocabulary for what is seen, a required structure for the report, a numbered assessment category summarizing the level of concern, and the recommendation that follows from that category. It also grades how dense the breast tissue appears on the images.
What do the categories mean?
| Category | Meaning | What follows |
|---|---|---|
| Zero | Assessment incomplete | More images, or comparison with older ones |
| One | Nothing abnormal seen | Return to routine screening |
| Two | A definitely harmless finding | Return to routine screening |
| Three | Probably harmless | Repeat imaging sooner than usual |
| Four | Suspicious | Tissue sampling advised |
| Five | Strongly suggestive of cancer | Tissue sampling, with treatment anticipated |
| Six | Cancer already proven by biopsy | Used while treatment is under way |
The numbers are not a scale of size or severity. Each states what the imaging suggests and what should happen next, and the first sits outside the sequence entirely, marking a study that cannot yet be assessed.
Why does the wording matter as much as the number?
Because the report is read by someone who never saw the images. Before the system existed, radiologists described findings in their own words, and terms such as suspicious or possible carried whatever weight the reader chose to give them. Two accounts of the same mammography study could lead to opposite decisions. The system fixes the descriptive terms instead: the shape of a mass, the character of its edge, the pattern of any calcium specks, and where in the breast it lies. Each carries an agreed meaning, so the final category follows from the description rather than from tone. That consistency also makes a service auditable, since real outcomes can be checked against what the reports predicted.
What does the density grade add?
A judgment about the background rather than about any finding. Dense tissue and cancer both appear white on a mammogram, so a dense breast hides small tumors more easily and the scan detects less in that person. Density is graded on a four-step scale running from almost entirely fat to extremely dense. It counts twice over: it warns the reader that a normal result offers less reassurance than usual, and dense tissue is itself associated with a higher chance of breast cancer. Density generally falls with age and cannot be judged by feel.
Also known as
Used in a sentence
The mammogram was reported under BI-RADS as suspicious, and a biopsy was arranged.
Good to know
The assessment categories state what the imaging suggests and what step follows rather than the size or severity of a finding, and category zero means the assessment is incomplete rather than that nothing abnormal was seen.