One of the most important aspects of starting your prostate cancer journey is understanding the pathology report from your prostate biopsy. This will include key information about how your doctor will counsel you on treatment options. At the time of your prostate biopsy, your urologist will send each piece of tissue to a pathologist who will look at each specimen under a microscope to determine if there is prostate cancer. If there is prostate cancer, there are several important aspects of the pathology to understand. The most common type of prostate cancer is adenocarcinoma, which is a type of cancer that develops in prostate glands.
What is the Gleason Grade/Gleason Score?
Pathologists use a scale from Grade 1 to 5 to describe how aggressive the prostate cancer cells look using the microscope. Typically, Grades 1 and 2 are not used for biopsies, thus the majority of biopsy samples are Grade 3 or higher. High grades of prostate cancer behave more aggressively: Grade 3 is low-grade prostate cancer, whereas Grade 5 represents very abnormal prostate cancer cells which typically act aggressively.
Since a biopsy specimen may have different areas with different grades of prostate cancer, pathologists will assign two grades for each positive specimen. The first number is the grade that is found most commonly in the specimen. The second number is the second most common grade in the specimen. For example, Gleason 4 + 3 prostate cancer means that the most common grade is 4 and the second most common grade is 3 for a Gleason score (or sum) of 7.
Of particular importance is Gleason score 7 prostate cancer, which can be either 3 + 4 = 7 or 4 + 3 = 7. Gleason score 3 + 4 prostate cancer, especially if low volume, may have a good prognosis. Gleason score 4 + 3 prostate cancer is more aggressive, although not as aggressive as Gleason score 8 disease.
The majority of positive specimens will have two Gleason grades. Occasionally, if there are three grades in a specimen, the pathologist may list the Gleason score (two most common grades) with an additional statement noting a tertiary grade (often “tertiary Gleason grade 5”). If the sample has all of the same grade of prostate cancer, then the Gleason grade is the same number for both the primary and secondary grades (i.e., 3 + 3). Additionally, different areas of the prostate may have completely different Gleason score disease (i.e., Gleason score 3 + 3 on the right and Gleason 4 + 3 prostate cancer on the left).
Generally, the highest Gleason score on the entire biopsy will be the driver of how your doctor counsels you on appropriate treatment options. Because a prostate biopsy only samples part of the prostate, the Gleason score does not represent the entire prostate. This means there may be more aggressive disease that was not biopsied and can only be assessed if the entire prostate gland is removed with surgery.
What are the Grade Groups?
There has been a recent push in the pathology and urology communities to assign a “Grade Group” to further stratify patients into appropriate cohorts, or groups, that may (or may not) need treatment. Because Gleason scores are often inappropriately lumped into three groups (6, 7, or 8-10), the Grade Group clearly separates these scores to provide clearer prognostication (predictions about how the disease will develop). The following are the Grade Group breakdowns:
- Grade Group 1 = Gleason score 6 or less
- Grade Group 2 = Gleason score 3 + 4 = 7
- Grade Group 3 = Gleason score 4 + 3 = 7
- Grade Group 4 = Gleason score 8
- Grade Group 5 = Gleason score 9-10
Other Important Aspects of the Prostate Biopsy Report
In addition to the grade of prostate cancer noted, the number of sites of disease (i.e., number of biopsy cores that show cancer), their location, and the amount of each core that has cancer (either taken as a linear measurement in millimeters or as a percentage of the length of the biopsy sample) provides important information to your doctor. The extent of cancer (i.e., more cores and a greater proportion of each core) can contribute importantly to treatment decision-making as this may affect your prostate cancer risk group.
There are nerves inside the prostate gland. When prostate cancer tracks along these nerves this is called perineural invasion. When this is seen under the microscope, it means that the prostate cancer has a higher chance of spreading outside of the prostate gland (although this does not mean that it definitely has spread outside the prostate gland). The pathologist may further note specific pathologic findings (including the presence of intraductal carcinoma or cribriform tumor pattern) that may indicate a more aggressive tumor. This information is taken into account with the rest of your information, such as your Gleason score and PSA blood test.
There are other, non-malignant (benign, or non-cancerous) findings that the pathologist may note on the biopsy. High-grade prostatic intraepithelial neoplasia (PIN) is a pre-cancer of the prostate, which is not typically important in making treatment decisions if other samples from your biopsy show prostate cancer.
Atypical small acinar proliferation (ASAP) means the pathologist sees cellular features under the microscope that are worrisome, but cancer is not explicitly present. However, again, if there are other samples on the biopsy that show prostate cancer, ASAP is not an important finding.
In addition to prostate cancer, your biopsy may also mention “acute inflammation” or “chronic inflammation.” Another term for these findings is prostatitis (not necessarily related to an infection), which has no additional bearing on your prostate cancer prognosis (how the disease may develop) or treatment. However, it may be an explanation for why your PSA blood test is elevated (particularly in situations when the PSA is higher than expected in relation to the prostate cancer Gleason score).
At your post-prostate biopsy clinic appointment, your doctor will go into detail about the information on the biopsy report and what it means for treatment options. The biopsy report includes information that— along with your PSA, age, and overall health—will be factored into appropriate treatment recommendations.