Understanding BI-RADS Category 3.

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• The Breast Imaging Reporting and Data System (BI-RADS) category 3 is defined as "probably benign" with <2% malignancy risk.
• Its application aims to enhance specificity and decrease unnecessary breast biopsies.
• Category 3 is validated for mammography and breast ultrasound, with emerging use in contrast-enhanced MRI.

Purpose of the Study:

• To clarify appropriate use and characteristic imaging findings for BI-RADS category 3 across different modalities.
• To address existing misuse and confusion surrounding BI-RADS category 3 assessments.
• To highlight the importance of short-term follow-up for category 3 findings.

Main Methods:

• Review of established BI-RADS category 3 criteria for mammography and breast ultrasound.
• Analysis of recent studies identifying characteristic findings for MRI category 3.
• Discussion of the role of short-interval imaging surveillance.

Main Results:

• Validated mammography findings for category 3 include grouped round calcifications, oval circumscribed masses, and nonpalpable asymmetries.
• Validated breast US findings include oval circumscribed parallel solid masses and complicated cysts.
• Emerging MRI findings for category 3 include oval circumscribed masses with T2-hyperintense signal, focal non-mass enhancement, and foci of enhancement with T2-hyperintense signal.

Conclusions:

• Accurate application of BI-RADS category 3 requires understanding specific imaging features and avoiding its use in screening without comprehensive evaluation.
• Short-term imaging surveillance is crucial for monitoring stability and detecting changes that may necessitate biopsy.
• Updated guidelines for MRI category 3 are anticipated in the sixth edition of the BI-RADS atlas.