Understanding Positive Biopsy Cores
What Are Positive Biopsy Cores?
During a prostate biopsy, a urologist removes multiple small tissue samples — called cores — from different areas of the prostate. Each core is then examined by a pathologist under a microscope.
A 'positive' core is one in which cancer cells were found. A 'negative' core showed no cancer. Your pathology report will tell you how many cores were taken and how many were positive — for example, '4 of 12 cores positive.'
Why Does the Number of Positive Cores Matter?
The number of positive cores gives your care team a sense of how much of the prostate is involved with cancer. More positive cores generally suggest:
- A larger volume of cancer within the prostate
- A higher likelihood that cancer may have spread beyond the prostate capsule
- A higher risk category overall
However, the number of positive cores is always interpreted alongside your Gleason score, PSA level, and other findings — not in isolation.
It is not just how many cores are positive, but where they are. Positive cores near the apex (bottom) of the prostate, near the seminal vesicles, or on both sides of the gland may have different implications than a single positive core in one location. Your report will describe the location of each positive core.
How Positive Core Count Is Used in Risk Assessment
Several widely used risk stratification systems incorporate positive core count. For example:
- The NCCN (National Comprehensive Cancer Network) guidelines use the number of positive cores as one criterion for distinguishing favorable from unfavorable intermediate-risk cancer.
- Having fewer than 50% of cores positive is generally considered more favorable than having 50% or more positive.
- Positive core count is also used in nomograms — mathematical tools that predict outcomes such as the probability of organ-confined disease or biochemical recurrence.
Unilateral vs. Bilateral Involvement
Your report may describe cancer as unilateral (found on one side of the prostate only) or bilateral (found on both sides). Bilateral involvement generally indicates more extensive disease and may influence surgical planning.
For men considering nerve-sparing surgery, knowing which side(s) are involved helps the surgeon decide how aggressively to preserve the neurovascular bundles.
Even one positive core with a high Gleason grade can indicate significant cancer. Conversely, multiple positive cores with low-grade cancer (Grade Group 1) may still be appropriate for active surveillance. The grade of the cancer in each core matters as much as the count.
When you see a result such as "4 of 12 cores positive," it is natural to focus on the number 4. But the number of positive cores is only part of the story.
Look at what was found in those cores too: the Gleason score/Grade Group, how much of each core contains cancer, where the positive cores were located, and whether cancer was found on one or both sides of the prostate.
A small number of positive cores can still contain higher-grade cancer, while a larger number of cores containing low-grade cancer may lead to a very different treatment discussion.
Ask your urologist:
"When you look at the number, location, grade, and amount of cancer in my positive cores together, what does that tell you about my overall risk?"