BI-RADS

What it means

Breast imaging — mammography, ultrasound, and MRI — needs a shared language so that a result means the same thing everywhere. BI-RADS (Breast Imaging Reporting and Data System) is that language: a single category that captures how concerning the images are and pairs each level with a clear recommendation, from routine screening to biopsy.

Why it appears on a CT or MRI report

The categories run 0 through 6. Category 0 means the study is incomplete and more images are needed. Category 1 is a normal study. Category 2 is a benign finding, such as a simple cyst. Category 3 is probably benign, with a short-interval follow-up (often six months) to confirm stability. Category 4 is suspicious and prompts a biopsy, sometimes subdivided 4A-4C by level of concern. Category 5 is highly suggestive of cancer. Category 6 is used when cancer is already proven by biopsy. The report gives the category and the recommended next step.

What it usually means

The overwhelming majority of screening results are category 1 or 2 — normal or benign — and simply mean returning for routine screening. A category 3 is reassuring but earns a follow-up scan rather than a biopsy, because the chance of cancer is very low but not zero. Categories 4 and 5 move toward tissue sampling, yet even here many category 4 findings turn out benign after biopsy. The category is a structured recommendation about what to do next, not a verdict about whether you have cancer.

When to follow up

Always follow the recommendation tied to the category: routine screening for 1-2, a timed follow-up for 3, and a biopsy discussion for 4-5. Do not skip a category 3 follow-up — its whole purpose is to catch the rare change early. Report any new breast lump, skin change, or nipple discharge to your doctor regardless of a prior category, since symptoms are assessed on their own.

A plain-language way to picture it

Think of it as a traffic system with clear instructions at each light. Green (1-2): drive on, come back at the usual time. Flashing yellow (3): slow down and check again shortly. Red (4-5): stop and take a closer look with a biopsy. Each color is not a destination — it is an instruction for the very next move.