Understanding Your Pathology Report: Prostate Cancer

What is a pathology report?

A pathologist is a medical doctor who specializes in diagnosing 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 report of their findings, which is called the pathology report.

You should get a copy of your pathology report for your personal health records and to share with the rest of your healthcare team. Understanding this report will help you in making treatment decisions.

What will you find on a pathology report?

The information in the report depends on how the prostate specimen was obtained. Prostate tissue samples can be from a biopsy or surgery. If you have a biopsy of your prostate, the pathologist will receive “cores” of prostate tissue (cylinder-shaped samples). If you have surgery, called a prostatectomy, the pathologist will receive samples of the entire prostate gland, seminal vesicles, vas deferens, and lymph node(s). The report is broken down into a few sections, including:

• 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 was received in 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 the Gleason grade and score (discussed below). The report will also say how much of the sample contained cancer. 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 Specimens

When a prostate biopsy is performed, 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 placed 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 specimens taken from a biopsy are called "cores.” Cores are are pieces of prostate tissue shaped like cylinders. The prostate is shaped like a chestnut and surrounds the urethra, where urine drains through. The cores are taken from the top (apex), middle, and bottom (base) parts of both lobes (sides) of the prostate gland.

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

Gross Description

For the most part, the gross description is not that important for your understanding of the report. It will describe how the specimens were received (in one container or several) and how they are labeled. It describes what the pathologist sees with the naked eye. In a biopsy, the specimen is likely a small, nondescript piece of tissue. 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 submitted 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" once the tissue is removed from the body. There may be mention of surgical clips or wires that were used by the surgeon to be sure that the suspicious area was removed.

The gross description tells us the size of the tissue submitted, but not the size of the actual cancer. The gross description isn't helpful in determining the stage of the cancer or which treatment might be best, which is important to you. 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 contains 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 discuss each part of the microscopic diagnosis section in detail. Sometimes the tests are performed in different laboratories or take different lengths of time to complete, which can mean you may not get all the 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 inflammation or infection 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 a cancer. PIN is thought to be a pre-cancer.
• Adenocarcinoma: The type of cancer that is found in 95% of prostate cancer cases. Other rare types, making up 5% of cases, are small cell, mucinous, endometrioid, transitional cell, squamous cell, basal cell, adenoid cystic, signet-ring cell, and neuroendocrine carcinomas. 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 named after Dr. Donald Gleason, the pathologist who first studied and made a scoring system of the aggressiveness of prostate cancers. This system helps us to separate the less aggressive prostate cancers from those that are more aggressive. In more technical terms, 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 when 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 manner.

The Gleason score is actually 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 most dominant 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.
• 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 discrepancies can happen because of an incomplete biopsy or the expertise of the pathologist. Because the pathologist’s interpretation is subjective (each pathologist may grade differently), 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.

The Gleason score has been very clearly linked with expected trends in biochemical (PSA) survival without relapse (cancer coming back) and overall survival. In other words, it is a very strong tool to predict the course of prostate cancer.

How much tumor is present?

This information can be given in a few ways. In a core specimen 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 (ex- tumor present in 4 out of 5 cores). This information can help determine the tumor’s overall size and aggressiveness.

A prostatectomy specimen 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 extends outside the prostate gland, this will be described as involving or extending beyond the prostate capsule (capsular involvement). If capsular involvement is present, 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 specimen 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 any 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), further 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. Different staging systems are used for each type of cancer. The staging system most commonly used for prostate cancers is the American Joint Committee on Cancer (AJCC) staging system. This system utilizes the extent of the primary tumor (labeled T0-4b), the absence or presence of cancer in the lymph nodes (Nx-3), and the existence of metastasis (Mx-1b) to assign a TNM rating, which makes up the stage of the cancer. See the article All About Prostate Cancer 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 discuss your treatment options with your healthcare team.