BIRADS Categories

Category 0 -- Incomplete
Your mammogram or ultrasound didn't give the radiologist enough information to make a clear diagnosis. Don't worry, this may mean that scar tissue from a previous surgery or biopsy may have shown up, or that a lump that is big enough to be easily felt isn't imaging clearly. You will need to have a follow-up image done.
Category 1 -- Normal
There are no suspicious masses or calcifications to report; tissue looks healthy.
Category 2 -- Benign or Negative
Breasts are same size and shape and tissue looks normal. Any cysts, fibroadenomas, or other masses appear benign.
Category 3 -- Probably Benign
There are no suspicious lesions, masses, or calcifications to report, but follow-up to confirm that no cancer exists is recommended. This may be needed if your radiologist does not have your baseline or previous mammogram for comparison.
Category 4 -- Possibly Malignant
There are some suspicious lesions, masses, or calcifications to report; a biopsy is recommended to check the suspicious area.
Category 5 -- Malignant
There are masses with an appearance of cancer. A biopsy is recommended to make an accurate diagnosis.
Category 6 -- Malignant Tissue from a biopsy has been examined and found to be cancerous, and treatment such as surgery, chemotherapy, and/or radiation is required.

_{Sources:
American College of Radiology. BI-RADS US (PDF document) Copyright 2004.
breastscore.com. Breast Ultrasound Computer-Aided Scoring For Level Of Suspicion To Cancer. Copyright 2004.
Christopher Comstock MD, Associate Clinical Professor, Director of Breast Imaging, UCSD Dept of Radiology, La Jolla CA. 8/31/07 interview.} PTable 1. Evidence Table for Clinical Management Recommendations for Mammograms by Breast Imaging Reporting and Data System (BI-RADS) Category
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Here is a table of the BIRAD scores.

BI-RADS Category	Assessment	Clinical Management Recommendation(s)	Strength of Recommendation	References	Comments on References
0	Assessment incomplete	Need to review prior studies and/or complete additional imaging	A	3	All or none study; consensus guidelines
1	Negative	Continue routine screening	A	3, 8	Consensus guidelines; validated clinical decision tool
2	Benign finding	Continue routine screening	A	3, 8	Consensus guidelines; validated clinical decision tool
3	Probably benign finding	Short-term follow-up mammogram at 6 months, then every 6 to 12 months for 1 to 2 years	B	3, 6, 8, 10–15	Consensus guidelines; cohort studies; large case series; validated decision tool; less patient stress; lowered costs with surveillance
4	Suspicious abnormality	Perform biopsy, preferably needle biopsy	A	3, 8–10	All or none study; validated clinical decision tool
5	Highly suspicious of malignancy; appropriate action should be taken.	Biopsy and treatment, as necessary.	A	3, 8–10	All or none study; validated clinical decision tool
6	Known biopsy-proven malignancy, treatment pending	Assure that treatment is completed