The Gleason score is the summation of the Gleason grades identified during histologic examination of the prostate.
Usually the Gleason score is the sum of the 2 most common patterns. Sometimes the third most common grade is reported, especially if it represents Grade 4 or 5.
General rules:
(1) If only 1 pattern is present, then the 2 value Gleason score is 2 times the pattern.
(2) If there are 2 patterns in equal amounts then the higher grade is considered the primary pattern.
(3) When reporting the Gleason score the primary and secondary patterns may be reported separately. This is often done with Gleason score 7 composed of patterns 3 and 4. A tumor with Gleason score 7 (4 + 3) tends to be more aggressive than one (3 + 4)
Implementation:
(1) Each pattern is compared to the other 4 patterns.
(2) The pattern is greater than the other 4 is the primary pattern.
(3) The pattern that is greater than the other 3 is the secondary pattern.
(4) The pattern that is greater than the remaining 2 is the tertiary pattern.
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