Breast imaging-reporting and data system (BI-RADS) assessment category 4

Last revised by David Luong on 27 Jun 2021

A BI-RADS 4 lesion under the breast imaging-reporting and data system refers to a suspicious abnormality. BI-RADS 4 lesions may not have the characteristic morphology of breast cancer but have a definite probability of being malignant. A biopsy is recommended for these lesions. If possible, the relevant probabilities should be cited so that the patient and her physician can decide on the ultimate course of action. BI-RADS 4 lesions can be further subclassified into:

  • BI-RADS 4A: low level of suspicion for malignancy and has a > 2% to ≤ 10% likelihood of malignancy4

  • BI-RADS 4B: moderate level of suspicion for malignancy and has a > 10% to ≤ 50% likelihood of malignancy4

  • BI-RADS 4C: high level of suspicion for malignancy and has a > 50% to < 95% likelihood of malignancy4

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Cases and figures

  • Case 1: BI-RADS 4 on combined imaging
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  • Case 2
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  • Case 3: BI-RADS 4c
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