Case 16 Answer 2
The positive biopsy rate that is published as a general guideline of what is appropriate in standard screening practice is about 30%. Thus, 2 of every 3 biopsies yield benign results. This is for a screening population only.
There is no published guideline for diagnostic mammography, but published studies suggest that this number should be even higher-- because patients coming to diagnostic work-up for breast problems (especially palpable lumps) have a higher likelihood of having cancer than those who are asymptomatic [Dee & Sickles, AJR, 2000].
Every radiologist practicing mammography is required to perform a medical audit of her/his practice, and this is one of the critical variables analyzed. If your positive biopsy rate is 10%, that means you are performing too many biopsies on benign findings biopsying in order to find a cancer. On the other hand, if your positive biopsy rate is 70%, that means you are not performing enough biopsies on some suspicious findings and likely missing cancers (or you are better at picking out cancers than the world's experts!).