An incomplete (BI-RADS 0) classification warrants either an effort to ascertain prior imaging for comparison or to call the patient back for additional views and/or higher quality films. A BI-RADS classification of 4 or 5 warrants biopsy to further evaluate the offending lesion.ACR Practice Guideline for the Performance of Ultrasound-Guided Percutaneous Breast Interventional Procedures Res. 29; American College of Radiology; 2009 Some experts believe that the single BI-RADS 4 classification does not adequately communicate the risk of cancer to doctors and recommend a subclassification scheme:
