Breast BI-RADS

3 things to know first

1. It is a communication tool, not a cancer diagnosis. BI-RADS helps radiologists tell doctors and patients what a finding means and what to do next.
2. Lower numbers are more reassuring. Categories 0–2 usually mean no immediate concern; categories 3–5 mean closer follow-up or biopsy may be needed.
3. It is used for mammogram, ultrasound, and breast MRI. The same scale applies across these imaging tests.

What it is

BI-RADS stands for Breast Imaging-Reporting and Data System. It is a standardized scoring system created by the American College of Radiology. After a breast imaging study, the radiologist assigns a category from 0 to 6. Each category has a defined meaning and recommended next step.

The categories are:

• 0: Incomplete — more imaging is needed before a final assessment can be made.
• 1: Negative — no significant findings; routine screening continues.
• 2: Benign — a non-cancerous finding; routine screening continues.
• 3: Probably benign — very low likelihood of cancer; short-term follow-up imaging is recommended.
• 4: Suspicious — there is a concern that warrants a biopsy. This category is sometimes divided into 4A, 4B, and 4C to indicate increasing suspicion.
• 5: Highly suggestive of malignancy — imaging strongly suggests cancer; biopsy is recommended.
• 6: Known cancer — cancer has already been diagnosed and imaging is being used for staging or follow-up.

Why it appears on your report

Radiologists use BI-RADS to make breast imaging reports consistent and clear. Instead of vague language, the category gives the referring doctor a specific signal about risk and the recommended action. Insurance and scheduling systems also use BI-RADS to authorize follow-up tests.

How serious is it

The seriousness depends entirely on the category:

• Categories 0–2: Usually not serious. Category 0 simply means the test is not finished.
• Category 3: Very low risk of cancer, typically less than 2%. Most findings are monitored rather than biopsied.
• Category 4: Intermediate suspicion. A biopsy is often recommended, but many category 4 findings turn out to be benign.
• Category 5: High suspicion. A biopsy is strongly recommended.
• Category 6: Already known cancer; imaging helps guide treatment.

Your doctor will explain what your specific category means for you.

When to seek care urgently

BI-RADS itself does not usually require emergency action. Seek urgent care if you notice new symptoms such as:

• A rapidly growing breast lump
• Skin dimpling or thickening that looks like an orange peel
• New nipple inversion or bloody nipple discharge
• Severe redness, warmth, and swelling of the breast with fever

What usually happens next

1. Read the full report. Look at both the BI-RADS category and the radiologist's description.
2. Discuss with your doctor. They will explain the recommended next step based on the category.
3. Follow the recommended action. This may be a repeat scan in 6 months, additional imaging, or a biopsy.
4. Keep up with screening. Even after a benign result, continue routine breast screening as recommended.

A simple analogy

Think of BI-RADS as a weather forecast scale. A score of 1 or 2 means clear skies. A score of 3 means a small chance of rain, so take an umbrella later. Scores of 4 or 5 mean a storm may be coming, so it is time to check the radar more closely.

Further reading

• American College of Radiology — BI-RADS
• CDC — What is breast cancer screening?