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

Last revised by Mohammad Taghi Niknejad on 23 Jun 2023

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 malignancy 4

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

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