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Gleason Grade and Score

The Gleason score was invented in 1966 by Dr. Donald Gleason, a pathologist. He based the score on information derived from studies of the biopsies of nearly 3,000 patients who had been diagnosed with prostate cancer. Pathologists worldwide rely on the Gleason score. The score provides an effective measurement that helps your doctor determine how severe your prostate cancer is, based on the appearance of the cancer cells when viewed under a microscope. All cancer looks abnormal to a pathologist, but low-grade cancers have cells that often look similar to healthy cells from the gland or organ that has been affected by the cancer. As a result, the pathologist can recognize that she's looking at prostate cells under the microscope. But when the cancer is aggressive, the cancer cells look less and less like normal prostate cells (or any other kind of cells).

Pathologists find the Gleason grading system to be very reliable. For example, if the Gleason score indicates that the cancer is an intermediate risk cancer (a Gleason score of 7) it nearly always is an intermediate risk. As a result, doctors can make predictions from Gleason grades. The more distorted and aggressive the cancer looks, the higher the Gleason grade, and the more aggressive the cancer behaves in the body.

How it works

The pathologist looks at the biopsied tissue samples through a microscope to determine where the cancer is the most prominent (the primary grade) and then where it's next most prominent (the secondary grade). Next, he assigns a score from 1 to 5 to each area: one score for the primary grade and one score for the secondary grade. The Gleason score is the sum of the primary and secondary grades.

The Five Gleason Grades

Grade 1: The least common pattern, especially in needle biopsies. Consists of a circumscribed mass of evenly placed uniform glands that closely resemble normal prostate glands
 

Grade 2: Cancer glands are similar to those seen in Grade 1 but do not form a circumscribed mass. There may be slight variation in size, shape, and spacing of the glands. The glands can be seen infiltrating (spreading) through the surrounding stroma. Click on Gleason Pattern 2
 

Grade 3: The most common pattern showing considerable variation in size, shape, and spacing of the glands. Irregular infiltration of the surrounding stroma may impart a ragged appearance to the cancer focus when seen at low-magnification under the microscope.Gleason Pattern 3
 

Grade 4: The most important feature of this grade is fusion of glands forming an anastomosing network punctuated by glandular lumens. Glands are no longer recognized as individual units.Gleason Pattern 4
 

Grade 5: The cancer cells form solid sheets and clusters or may infiltrate the prostate as individual cells. Necrosis may be present. There is no attempt at gland formation by cancer.Gleason Pattern 5
 

The Significance of the Gleason Score

The Gleason score indicates the aggressiveness of the prostate tumor. Patterns 1 and 2 are well differentiated; Pattern 3 is moderately-differentiated; and Patterns 4 and 5 are poorly differentiated. What is differentiation? Well, cells that are completely differentiated know exactly what they are doing in life. Perfectly differentiated prostate cells are happy to go about their business in the prostate making PSA and ejaculatory juices. They look and act like the mature prostate cells they are. They interact with other perfectly differentiated prostate cells to create the tiny tubular structures that the prostate requires to deliver its product to the urethra. Once they become malignant, however, the prostate cells become less differentiated and behave less like well-disciplined prostate cells. The tubules they make with other malignant cells are distorted and haphazardly arranged. As they become even less differentiated, they form solid clumps and may become anti-social, preferring to go off on their own and not even attempt to make tubules with other cells.

Interpreting the Results

The Gleason score is written as the sum of the two most prominent Gleason patterns. The lowest possible Gleason score is 1+1=2 when both the primary and secondary patterns are Grade 1. The highest possible Gleason score is 5+5=10 when both the primary and secondary patterns are Grade 5 .  So a Gleason score of 2+3=5 has a dominant well-differentiated pattern (i.e., pattern 2) and a less dominant moderately-differentiated pattern (i.e., pattern 3). A score of 4+3=7 means that a poorly differentiated component (pattern 4) is dominant. If 95% or more of the tumor is composed of one pattern, the corresponding number is counted twice; thus, a wholly moderately-differentiated tumor would be scored 3+3=6. Note: not all scores are equal. A score 7 from 3+4 is better than one from 4+3. So if you want to know the real deal on your Gleason score, get a breakdown of the two numbers that comprise the score. Ask your doctor for your Gleason score, starting with the primary grade first, followed by the secondary grade and then the total.

The Gleason score is determined by the pathologist, a physician who spends much too much time looking at little squiggly things through his microscope. I have seen cancers reported out as 2+3=6. This means that the pathologist has a difficulty with math.

Gleason scores can be determined by examining prostate biopsies or they can be determined by examining the entire prostate after the prostate is removed surgically. Since the biopsies represent only a small portion of the entire prostate, they may not be representative of the entire gland as a whole. The Gleason score as determined from the biopsy specimen, however, has been shown to be one of the strongest prognostic factors available. An accurate Gleason score can help one decide which treatment may be beneficial.