The 5-tier ACR system was a previously used system for classification of radiologic breast findings, proposed by the American College of Radiologists (ACR). It is no longer in widespread use, having been gradually superseded by the new 6-tier BIRADS classification system first published in 1992.
- 5: malignant
- 4: probably malignant: biopsy should be considered
- 3: probably benign: initial short term follow up recommended
- 2: benign
- 1: normal
- 0: need additional views