The 5-tier ACR system was a previously used system for classification of radiologic breast findings, proposed by the American College of Radiology (ACR). It is no longer in widespread use, having been gradually superseded by the 6-tier BI-RADS classification system first published in 1992.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