Understand your BI-RADS score
Your mammogram report ends with a number nobody explained. Here is what each category means, what happens next — and why category 4 is not stage 4.
Find the two results on your report
A mammogram report carries two separate graded results, and they are routinely confused with each other.
- Assessment category — a number from 0 to 6. How suspicious the radiologist finds the picture.
- Breast density — a letter from A to D. How much dense tissue you have. Not a measure of risk from this scan.
The category is the radiologist telling you how confident she is — like a weather forecast giving a chance of rain. A forecast is not the weather, and a category is not a diagnosis.
Most findings placed in category 4 turn out not to be cancer. The number describes the picture, not you.
What each category means
The categories are a scale of concern, not a scale of severity. Each one carries a different next step. Find yours.
Category 0
Incomplete
More images needed. This is not a finding.
Category 1
Negative
Nothing found. Back to routine screening.
Category 2
Benign
Clearly not cancer. Back to routine screening.
Category 3
Probably benign
Short-interval follow-up to confirm it does not change.
Category 5
Highly suggestive
Biopsy strongly advised. Planning often begins in parallel.
Category 6
Already confirmed
A biopsy has already proven cancer. The scan is for planning.
Not sure which category you have been given? Send us your report. A specialist will tell you what it says and whether anything needs doing now.
Get my scan report explainedLook up your category
Tap the number on your report to see what it means, how worried to be, and what usually happens next.
If your report shows a letter A to D as well, that is breast density — a separate thing. Explained below ↓
Category 3
Very likely harmless. The radiologist is not worried, but wants to confirm the finding does not change over a short interval.
What usually happens: a repeat scan after a short interval rather than a biopsy. If nothing changes, you return to routine screening.
General explanations to help you follow your own report — not a diagnosis, and no substitute for a specialist reading your images. No category is a confirmed cancer; only a biopsy can decide that. Call 1800 202 8726 if your report does not match anything here.
All categories
- Category 0
- Incomplete — more images needed. Not a finding.
- Category 1
- Negative — nothing found. Routine screening.
- Category 2
- Benign — something seen, clearly not cancer. Routine screening.
- Category 3
- Probably benign — short-interval follow-up to confirm no change.
- Category 4A
- Low suspicion — biopsy advised. Most turn out benign.
- Category 4B
- Moderate suspicion — biopsy advised.
- Category 4C
- High suspicion — biopsy advised. Still not a diagnosis.
- Category 5
- Highly suggestive — biopsy strongly advised.
- Category 6
- Already biopsy-proven. The scan is for planning or monitoring.
BI-RADS 4 is not stage 4
This is the single most distressing misreading of a mammogram report, and it happens constantly. They are not the same scale, and not even the same subject.
- A category describes the photograph, before anyone knows what the finding is.
- A stage describes a confirmed cancer and how far it has spread — and it can only be given after a diagnosis.
Both use small numbers, and that is the only thing they share. A hotel star rating and a room number use the same digits and mean completely unrelated things.
If you have been given a category 4, you do not have a stage. You have a recommendation for a biopsy. How staging actually works →
Category 4 comes in three strengths
If your report says 4A, that is the mildest of the three — and most people reading a bare "4" assume the worst available meaning of the number.
The letters are not degrees of how bad it is. They describe how strongly the picture argues for a biopsy. All three end in the same place — a biopsy, which is the only thing that actually decides.
Even 4C is not a diagnosis. It is a strong reason to find out.
Dense breasts — why your report mentions this
Density is reported on every mammogram, as a letter from A to D. It is not a disease and not a diagnosis — it describes how much dense tissue you naturally have.
It matters for one practical reason, and it explains why an ultrasound is often added.
On a mammogram, dense tissue is white and a lump is also white. It is like trying to spot a white cricket ball on a white bedsheet instead of on a green field.
Dense breasts are a normal finding, and they are more common in younger women. If your report mentions density, it is telling the next doctor how easy or hard the picture was to read.
Decode a word from your scan report
The descriptive words on a mammogram report are the most opaque part of it. Tap any you can see.
Mass
A three-dimensional lump the radiologist can see on more than one view. The word says nothing about whether it is harmless.
Why it matters: what follows it on the report — the shape and the margin — is what actually moves the category up or down.
General explanations to help you follow your own report — not a diagnosis. If a word on your page isn’t here, call 1800 202 8726.
All terms
- Mass
- A three-dimensional lump seen on more than one view. Says nothing yet about whether it is harmless.
- Calcifications
- Specks of calcium. Extremely common and mostly harmless; the pattern is what matters.
- Microcalcifications
- Very fine specks. Assessed by pattern — scattered is ordinary, tightly clustered needs a look.
- Asymmetry
- One breast shows tissue the other does not, at the same spot. Often normal variation.
- Architectural distortion
- The tissue lines look pulled, without a clear lump. Worth investigating because it can be subtle.
- Cyst
- A fluid-filled sac. Very common and not cancer.
- Fibroadenoma
- A common benign solid lump, most often in younger women.
- Circumscribed
- The edge is smooth and clearly defined. Usually reassuring.
- Indistinct
- The edge cannot be clearly made out. Not alarming on its own; it means less certainty.
- Obscured
- The edge is hidden by overlying tissue rather than being genuinely unclear.
- Spiculated
- The edge has fine spikes radiating outward. This raises suspicion.
- Lobulated
- A gently wavy outline with rounded bumps. Usually a mild descriptor.
- Skin thickening
- The skin over the breast looks thicker than expected. Has many causes, including infection.
- Breast density A–D
- How much dense tissue you have, A to D. A normal finding, not a diagnosis.
- Fibroglandular
- The normal working tissue of the breast, as opposed to fat.
- Heterogeneously dense
- Density category C. Enough dense tissue that a small finding could be hidden.
- Involuted
- Dense tissue has naturally been replaced by fat over time. Makes scans easier to read.
- Short-interval follow-up
- A repeat scan sooner than routine, to confirm a finding has not changed.
- Ultrasound correlation
- An ultrasound is added to look more closely at what the mammogram found.
- Diagnostic mammogram
- A targeted scan of a specific concern, rather than a routine screening scan.
- Tomosynthesis / 3D
- A mammogram taken in thin slices, which reduces the tissue-overlap problem.
- Stereotactic biopsy
- A needle biopsy guided by mammogram images, used for findings that cannot be felt.
What to do next
Get the images, not just the report
Ask for the films or the CD. Any second reading needs the images themselves, not the printed summary.
Note the exact category
Including the letter if there is one. 4A and 4C lead to the same next step but very different levels of concern.
Do not wait on a category 4 or 5
Both mean a biopsy is advised. Booking it is the fastest route out of uncertainty.
Been advised a biopsy? How to read the report you will get →
Not sure what your next step should be?
Send us the report and the images. A specialist will tell you whether the recommended next step is the one we would advise.
Or call 1800 202 8726 — toll free, no obligation.
Support that comes with your care
If your scan does lead further, these run alongside treatment at CION rather than as afterthoughts.
Nutrition
Appetite, weight and strength through treatment.
Psychology
Support through uncertainty, for patient and family.
Genetic counselling
Hereditary risk for you and close relatives.
Rehabilitation
Shoulder mobility and lymphoedema care.
Screening
Regular checks for you and close relatives.
Second opinion
A written review of your scan and plan.
We will tell you what your category actually means
A specialist will read your report and your images, explain the category in plain terms, and tell you whether the recommended next step is the one we would advise. Bring the films or the CD if you have them.
Toll free 1800 202 8726 · Advancing Care. Passionately.