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5-tier ACR system of radiologic breast findings

Last revised by Dr Daniel J Bell on 14 Nov 2019

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 It is no longer in widespread use, having been gradually superseded by the 6-tier BI-RADS classification system first published in 1992. Interestingly, despite its name, it was actually a 6-tier system!

  • 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

See also

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