Understanding Your Pathology Report: Prostate Cancer

What is a pathology report?

A pathologist is a medical doctor who uses laboratory tests and techniques to help diagnose diseases. Pathologists look at tissue from the body that is removed during surgery or a biopsy. You will probably never meet the pathologist, but samples of your prostate tissue will be sent to them for review. The pathologist prepares a summary of their findings, which is called the pathology report.

You should get a copy of your pathology report for your personal records and to share with your healthcare team. Understanding this report can help you when making treatment decisions.

What will you find on a pathology report?

The information in the report depends on the method used to get a sample of your prostate tissue. Prostate tissue samples can be from a biopsy or surgery. If you have a biopsy of your prostate, the pathologist will get “cores” of prostate tissue (cylinder-shaped samples). If you have surgery, called a prostatectomy, the pathologist will get samples of the entire prostate gland, seminal vesicles, vas deferens, and lymph node(s). The report has a few sections:

• Some information about the patient.
• Diagnosis (suspected or known).
• The procedure that was done to get the prostate tissue.
• The date the specimen was collected and when it got to the laboratory.
• A description of what the specimen looks like to the naked eye (called gross description).
• A description of what was seen under the microscope (microscopic description).
• A pathologic diagnosis (a diagnosis based on what the pathologist saw under the microscope.

If there are any tissue pieces that have cancer cells, the pathologist will give a Gleason grade and score (discussed below). The report will also say how much of the sample had cancer cells. While all reports will have this information, the words they use may be different. To help you read your report, let’s go through each of these sections.

Types of Samples

When a prostate biopsy is done, the physician takes 10 or more samples from many areas of the prostate gland. These samples are taken using one of two biopsy methods:

1. Transrectal Biopsy (through the rectum): Uses a small ultrasound probe put into the rectum to guide the biopsy needles through the rectal tissue into the prostate. This is the most common biopsy done for the prostate.
2. Transperineal Biopsy (through the perineum): Needles are placed through the perineum (the skin between the scrotum and rectum) into the prostate tissue. 

The tissue samples taken from a biopsy are called "cores.” Cores are pieces of prostate tissue shaped like cylinders. The prostate is shaped like a chestnut and wraps around the urethra (where urine leaves your body). The cores are taken from the top (apex), middle, and bottom (base) parts of both sides of the prostate gland.

When a prostatectomy is done, the entire prostate gland is taken out along with nearby fat and tissue. The sample may include the seminal vesicles (glands that produce about 60% of semen volume) and the vas deferens (the tube that semen passes through). The sample may also have one or more lymph nodes.

Gross Description

The gross description describes how the prostate samples were received (in one container or several) and how they were labeled. It describes what the pathologist sees with the naked eye. The pathologist may describe the color, shape, feeling, and size of the tissue. After prostate surgery, large pieces of tissue and lymph nodes may be looked at and described in the report. This description might report the presence of "inked" margins or sutures, which the surgeon adds so the pathologist can tell "which end is up" after the tissue is taken out of  the body. The report may also mention surgical clips or wires that were used by the surgeon to be sure that the suspicious area was taken out. 

The gross description tells you the size of the tissue, but not the size of the actual cancer. The gross description isn't helpful in determining the stage of your cancer or which treatment might be best. We will discuss these in the next sections. 

Microscopic Diagnosis

This section may be called “microscopic diagnosis,” “description,” or just “diagnosis.” This part of the report has the most useful information to you. Not every report goes through the microscopic diagnosis in the same order. Some use different terms to describe the same thing. In this section, we will go over each part of the microscopic diagnosis section in detail. Sometimes the laboratory tests are done in different laboratories or take different lengths of time to complete, so you may not get all your results at once. It is important to wait for all the results to best understand your case.

Terms used to describe the tissue:

• Benign tissue: Tissue that is not cancerous.
• Tissue inflammation or prostatitis: This means there was inflamed tissue, which can be the cause of a high Prostate-Specific Antigen (PSA) level when cancer is not found.
• High-grade prostatic intraepithelial neoplasia (PIN): A benign (non-cancerous) condition that is often seen along with cancer. PIN is thought to be a pre-cancer.
• Adenocarcinoma: The type of cancer that is found in 95% of prostate cancer cases. This article will only address adenocarcinomas.

If the pathologist finds adenocarcinoma in your prostate tissue, more details about the cancer will be in the pathology report. These sections are discussed below. 

Gleason Grade and Score

The Gleason score is a system that helps us to separate the less aggressive prostate cancers from those that are more aggressive. It represents the "grade" of the tumor, which is the degree of differentiation of prostate cancer cells. Differentiation refers to how "normal" a cancer cell looks under a microscope compared to a normal prostate cell. 

• Poorly differentiated or undifferentiated: The cancer cells look much different than normal, healthy cells.
• Well differentiated: The cancer cells look similar to normal, healthy cells.

As you might expect, more aggressive cancers are poorly differentiated. More aggressive, poorly differentiated tumors have a hard time controlling their growth, which lets them multiply in an uncontrolled way.

The Gleason score is a sum of two Gleason grades. The grade is a number from 1-5, with 1 being the most well differentiated (least aggressive) and 5 being the most poorly differentiated (more aggressive) pattern. The pathologist gives a primary grade to the tumor cells that make up the majority of the tumor and a secondary grade to the cells making up a minority of the tumor. The Gleason score is the sum of these two grades. The range of Gleason scores could be from 2 (1+1) to 10 (5+5). The most prominent (primary) grade is either reported as the Gleason grade or is the first number in the score. For example:

• In a report of Gleason 7 (3+4), grade 3 is the most prominent, making up a majority of the tumor.
• In a report of Gleason grade 4, score 7; grade 4 is the most prominent, with the total score being 7 (therefore grade 3 is the second most prominent score).

Often, when a prostate is biopsied for diagnosis and then removed later with a radical prostatectomy, Gleason scores are the same between the biopsy and surgery specimens only 75% of the time. In about 20% of the cases, the surgery specimen actually ends up having a higher Gleason score (a more aggressive cancer) than what had been found on the initial biopsy. The reverse (lower Gleason score at surgery than at biopsy) happens less than 5% of the time. These differences can happen because of an incomplete biopsy or the expertise of the pathologist. A pathologist’s interpretation is subjective (each pathologist may grade differently), so it is important to have your tumor reviewed by an expert pathologist. Many experts recommend having a second pathologist look at the specimen to be sure the Gleason grading is correct.

Your Gleason score is a very strong tool to predict the course of your prostate cancer.

How much tumor is present?

This information can be given in a few ways. In a core sample from a biopsy, the pathologist may report the amount using a measurement in millimeters and/or a percentage of the core. They will also say how many cores had cancer cells (for example: tumor present in 4 out of 5 cores). This information can help determine the tumor’s overall size and aggressiveness.

A prostatectomy sample report will describe what percent of the gland has cancer. The prostate is made up of a central zone, transitional zone, and peripheral zone. The pathologist will identify which zones have cancer. If the tumor goes outside the prostate gland, this will be described as involving or extending beyond the prostate capsule (capsular involvement). If there is capsular involvement, the report may give the percent of involvement. The pathologist also looks at the seminal vesicles for any cancer cells.

Your report may comment on margins. This is the area at the edge of the sample that was submitted. When performing a cancer surgery, the surgeon attempts to remove the entire tumor and some normal tissue around it. This area of "normal tissue" is important because stray cancer cells may be included in this. If the edge (or margin) contains tumor, there may have been cancer cells left behind. The goal of surgery is to have a "clear margin,” that is, clear of any cancer cells. In the case of a positive margin (that has cancer cells), more treatment may be needed. 

If a prostatectomy sample has surrounding fat and/or lymph node(s), the pathologist will note if these tissues contain cancer cells.

Staging

"Staging" is used to describe and group cancers based on the size and extent of the tumor. The staging system most often used for prostate cancers is the American Joint Committee on Cancer (AJCC) staging system. This system uses the extent of the primary tumor (labeled T0-4b), if there is cancer in the lymph nodes (Nx-3), and if there is metastasis (Mx-1b) to give a TNM rating, which makes up the stage of the cancer. See the article  Prostate Cancer: Staging and Treatment for complete staging information.

Putting it all together

In prostate cancer, both Gleason score and staging are used to predict the aggressiveness of the cancer and what treatment is needed. By understanding the basics of the report, you will be better able to talk about your treatment options with your healthcare team.