The American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS)

There are 7 ACR BI-RADS standardized categories:

• Category 0, or "need additional imaging evaluation," is used if additional imaging is needed (this category is almost always used in a screening situation and should be used only rarely after a full imaging workup; additional imaging evaluation includes the use of spot compression and magnification views, along with other tailored mammographic views and ultrasonography).
 
• Category 1, or "negative," is used if there are no findings to comment on; for example, the breasts are symmetrical, and no masses, architectural disturbances, or suspicious calcifications are present.
 
• Category 2, or "benign finding(s)," is used if the radiologist wishes to describe a benign finding while still concluding that there is no mammographic evidence of malignancy.
 
• Category 3, or "probably benign finding initial short-interval follow-up suggested," is used when a noted finding has a very high probability of being benign; the finding is not expected to change over the follow-up interval, but the radiologist prefers to establish its stability over time.
 
• Category 4, or "suspicious abnormality–biopsy should be considered," is used when a finding has a definite probability of being malignant.
 
• Category 5, or "highly suggestive of malignancy–appropriate action should be taken," is used when a finding has a high probability of being cancerous. 
 
• Category 6, or "known biopsy-proven malignancy-appropriate action should be taken," is "reserved for lesions identified on imaging study with biopsy proof of malignancy prior to definitive therapy".