A mammogram is read by a radiologist, and a report of the findings is prepared for the patient’s doctor. In the United States the mammogram report is required to include a final assessment or management recommendation for the patient. Most radiologists use a standardized reporting terminology developed by the American College of Radiology known as BIRADSTM.

In BIRADSTM there are seven categories:

0 – abnormal screening, needs additional views
1 – negative
2 – benign findings
3 – probably benign findings
4 – suspicious
5 – highly suspicious for malignancy
6 – known cancer

It is the Category 3 “Probably Benign” report that sometimes causes anxiety on the part of the patient. Most often category 3 mammograms are followed in 6 months rather than 1 year.

Typically, the BIRADSTM 3 – “probably benign” category accounts for a small number of mammograms read. This designation should not be based on a screening mammogram alone, but instead follows a diagnostic mammogram and possible ultrasound. Based on this more extensive evaluation, the features of the lesion are considered very likely benign and not suspicious enough to warrant a biopsy. The likelihood that a probably benign lesion is actually a breast cancer is less than 2%. These lesions are typically followed carefully with diagnostic mammography at 6 months intervals at least for 1 year, then yearly thereafter. This is a safe interval to follow the abnormality in the very small chance that there would be a change. If for any reason there is an increase is size of the lesion at any point, needle biopsy is usually recommended.

Take home points:

• The “Probably benign” designation on mammography occurs after a careful diagnostic mammogram to evaluate an abnormality found on a screening mammogram.
• “Probably benign” finding have a greater than 98% probability of representing a benign lesion.
• “Probably benign” lesions are followed with diagnostic mammography at a shorter interval (usually 6 months).

By Ellen Shaw de Paredes, MD, FACR