The probably benign assessment.

The probably benign assessment (category 3 in the Breast Imaging Reporting and Data System) is associated with a less than 2% probability of malignancy. Its use in mammography is well supported by robust data from various large-scale prospective studies. Use of the probably benign assessment for lesions visible only at ultrasound or MR imaging is much less well established. This article examines in depth the use of the probably benign assessment: which lesions should be assessed as probably benign, the published evidence supporting such use, pitfalls in misuse, and areas of potentially expanded use that currently are under investigation.