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Gleason Grading
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, prefering to go off on their own ands not even attempt to make tubules with other cells.
The Gleason score is written as the sum of the two most prominent Gleason patterns. 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. 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.
Warning: The term "Gleason Grade" is hopelessly confusing. Both doctors and patients alike use this term for both Gleason score and Gleason pattern. Since the highest pattern is 5, when one hears the term Gleason grade 6 or higher, one can assume that Gleason score is meant. On the other hand, a Gleason Grade 3 or 4, could refer to both a Gleason pattern or a Gleason score. It is always wise to avoid confusion, Kimosabe.