As far as I know - about 70/75% of biopsies return benign results.
The problem with biopsies is false negatives. Take the following with a grain of salt, but if interested, one can check it further
“Based on the search results, there are a few key reasons why prostate biopsies can have a high rate of false negatives:
1. Prostate biopsies only sample a small portion of the prostate gland (less than 1%), so cancer can be missed if it is located in an unsampled area[1][2][3].
2. Prostate cancer can be difficult to detect, especially in its early stages. Factors like younger patient age, smaller prostate size, lower PSA levels, and lower Gleason scores can all contribute to a higher false negative rate[1].
3. The 12-core biopsy technique, while more comprehensive than earlier sextant biopsies, still has a considerable false negative rate of around 30-40% [4]. Repeat biopsies are often needed to detect cancer that was missed initially.
4. Limitations of the imaging techniques used, such as transrectal ultrasound, can make it challenging to visualize and target all suspicious lesions within the prostate[2][3].
5. There is inherent variability in how prostate biopsy samples are interpreted by pathologists, which can lead to some cancers being missed[1].
In summary, the small sampling size, difficulty in detecting early-stage prostate cancer, and limitations of current diagnostic tools all contribute to the high false negative rates associated with prostate biopsies. Improved imaging techniques and risk stratification methods are needed to enhance the accuracy of prostate cancer detection[3][5].
