The BI-RADS System
Table 1 presents BI-RADS classifications and management recommendations as an evidence table. Classifications are divided into an incomplete assessment (category 0) and completed assessments (categories 1, 2, 3, 4, 5, 6).[1,3] Although there are 7 assessment categories, only 4 outcomes are possible: (1) additional imaging studies, (2) routine interval mammography, (3) short-term follow-up, and (4) biopsy. All categories reflect the radiologist's level of suspicion for malignancy, and these assessment categories have been shown to be correlated with the likelihood of malignancy. Because each BI-RADS category has only one specific recommendation, this system can both inform family physicians about findings and direct appropriate follow-up and management.
The BI-RADS lexicon offers a number of strengths, including the application of a standardized common language to facilitate communication between radiologists, referring physicians, and patients. The system also clarifies the reporting of mammography results and will support the completion of quality improvement activities and clinical research.
The vast majority of screening mammograms are classified as BI-RADS 1 and 2. Between 5% and 9% of screening mammograms will require additional follow-up or biopsy including up to 7% of mammograms classified as BI-RADS category 3 as well as the 2% of BI-RADS 4 or 5 mammograms.[5,6,7] The positive predictive value of a biopsy positive for malignancy increases from <2% for BI-RADS category 3 mammograms to 23% to 30% for category 4 mammograms and to 95% for category 5 mammograms.[8,9] Specific mammographic features with the highest positive predictive value of malignancy include masses with spiculated margins and/or irregular shape, as well as calcifications with linear morphology and/or segmental distribution.
Table 2 summarizes findings from a population-based mammography registry in New Hampshire showing the proportion of breast cancers observed by BI-RADS category. The rate of breast cancer among women with BI-RADS category 1, 2, or 3 mammograms after 1 year of follow-up was approximately 1/1000 compared with 136/1000 among those with category 4 and 605/1000 with category 5 mammograms.
J Am Board Fam Med. 2006;19(2):161-164. © 2006 American Board of Family Medicine
Cite this: BI-RADS Classification for Management of Abnormal Mammograms - Medscape - Mar 01, 2006.